BRIEF REPORTS / RAPPORTS BREFS
Sensory irritation response in mice to sulfur dust C H R I S ~ P HBE E RVAN^
AND
FREDERICK T. WHITMAN
Can. J. Physiol. Pharmacol. Downloaded from www.nrcresearchpress.com by San Diego (UCSD) on 01/08/15 For personal use only.
Exxon Biomedical Sciences Inc., Mettlers R~cad,CN 2350, East Milbstone, N. J. 08875, U.S. A. Received April 88, 1992
BEVAN,C., and WHITMAN, FaT. 1992. Sensory irritation response in mice to sulfur dust. Can. J. Physiol. Bkarmacol. 70: 1291 - 1293. The potential of sulfur dust to produce sensory irritation was evaluated in mice. Male Swiss- Webster mice were exposed by head-only inhalation to 104, 263, or 458 mg/m3 sulfur dust aerosol at room temperature. Breathing frequency and patterns were monitored before, during, and after exposure to evaluate the animal's sensory irritation response to the test atmosphere. Group average breathing rates were decreased 7 and 17% below pretest values in mice exposed to 104 and 243 mg/m3, respectively; however, breathing patterns appeared normal, indicating that there was no sensory irritation. Mice exposed to 451 mg/m3 showed an increase in breathing frequency of 776, with 114 mice displaying very slight signs of pulmonary (deep lung) irritation. Some of the mice in the low- and high-dose groups exhibited signs of slight eye irritation immediately after exposure, but all mice were normal 1 day later. On the basis of these findings, exposure to sulfur dust up to 451 mg/m3 did not produce any sensory or upper airway irritation in mice. Key words: sensory irritation, sulfur dust, dust aerosol. BEVAN,C., et WHITMAN, E Te 1992. Sensory irritation response in mice to sulfur dust. Can. J . Physiol. Pharn~acol.70 : 1291 - 1293. On a CvaluC la capacitC de fines particules de soufre de provoquer une irritation sensorielle chez les souris. On a expos6 des ssuris Swiss-Webster males B 106, 263, ou 451 mg/m3 de poussikre de soufre en airosol, B temperature ambiante. On a enregistre la frtquence et les profils respiratoires avant, pendant et aprks l'exposition, pour Cvaluer la rCponse de 19irritation sensorielle des animaux ii lqatmosphbre-test. Ees taux respiratoires moyens des groaapes ont dirninue de 7 et de 17% au-dessous des valeurs pr6test chez les souris expostes il 106 et 263 mg/m3, respectivement; toutefois, les profils respiratoires ont sernblC normaux, indiquant B'absence d'irritation sensorielle. Les souris exposkes B 451 rng/m3 ont montre une augmentation de la frkqaaence respiratoire de 7 % , le 114 des souris pr6sentant de trks lCgers signes d'irritation pulmsnaire (poumon infbrieur). Quelques souris des groaapes avec dose faible et dose forte ont prksentt des signes de ICgkre irritation oculaire imm6diatement aprks l'exgosition, mais celle-ci avait dispam le lendemain. D'aprks ces rbsultats, une exposition A plus de 451 mg/m3 de poussikre de soufre n'a provoqub ni irritation des voies aeriennes supCrieures ni irritation sensorielle chez les souris. Mots clds : irritation sensorielle, poussikre de soufre, poussikre en abrosol. [Tradeait par la rddaction]
The Provincial Government of Alberta has set the occupational exposure limit for sulfur dust at 16 mg/m3 on the assumption that sulfur dust is a nuisance dust with no intrinsic tcexicologicd properties. Because little is known about the irritating properties of sulfur dust, the potential s f sulfur dust to produce an upper airway or sensory irritation response was investigated. The test system that. was chosen for the present study was an Alarie test (Alarie 1966), which measures the ability of a chemical to activate the trigerninal nerve endings in the nasal passages (Meele 1962; Cauna et a&.1969). A sensory irritant, when inhaled via the nose, will stimulate the trigeminal nerves, evoking a painful burning sensation of the nose and throat. In an acute exposure, this stimulation occurs in the absence of any histological damage to the nasal epithelium. The Alarie test has been validated for a wide range of gaseous and liquid aerosol irritants, covering a broad range of exposure concentrations and particle sizes (Marie 1993, 1981). The model involves two respiratory parameters: breathing pattern and frequency. The breathing pattern identifies whether the irritation is an upper airway response or a 'Author for correspondence. Printed in C a n d a 1 Imprim6 au Canada
lower (pulmonary) response, and the breathing frequency is used to measure the sensory irritation response. The decrease in breathing frequency observed with sensory irritants has been shown to be concentration dependent and can be quantitated to yield the RD5() (the exposure concentration that reduces the breathing frequency by 50%). The present study has characterized the type and degree sf change in respiratory behavior at sulfur dust concentrations in the range 100450 rng/m3.
Materials and methods Aazimals Male Swiss -Webster mice were supplied by Charles River B r e d ing Eaboratgbries (Portage, Michigan) and were approximately 6-7 weeks of age at the time of the study. Animals were housed individually in elevated, stainless steel wire mesh cages and maintained on a 12 h light : 12 h dark cycle. Animals were maintained and monitored in accordance with the Guide for the Care and Use of h b o r ~ t o r y Animals (1985). Food ( h r i n a 5002) and tap water were provided ad libitum. Room temperature and humidity were maintained at a range from 22 to 24'C and 41 to 69% respectively. '@,
Aerosol generation and exposure measurements Solid sulfur in the form of yellow pellets or chunks was obtained through the Canadian Petroleum Association. The test mterial was composed of a mixture of samples from each of the participating com-
CAN. J. PHYSIOL. PHAWMACOL. VOL. 70, 1992
1292
TABLE 2. Sensory irritation response of mice to sulfur dust aerosol
TABLE1. Characterization of the sulfur dust aerosol Sulfur dust exposure group Low Nominal chamber concn. (rng/rn3)"
Can. J. Physiol. Pharmacol. Downloaded from www.nrcresearchpress.com by San Diego (UCSD) on 01/08/15 For personal use only.
Actual chamber concn. (rnglrn")"
Middle
1205
2410
106
263
Response ($6 of control values)
High 3359 451"
Exposure (mfdm')
Exposure period
Recovery period
Particle sizea 50% size (pm) Geometric SD NOTE:Values represent the mean f SD, ?= l
"Value represents a single sample. b ~ a l u represents e the mean of two samples.
panies and was comidered to be representative of current production, taken directly after the sulfur-forming operation or from the sulfur pit. Solid sulfur was hand ground with a mortar and pestle at room temperamre and passed through a 60-mesh sieve. The dust was compressed and made airborne using a Wright Dust Feeder, which expelled the dust aerosol into a glass premixing vessel. The dust aerosol was then delivered into an -4-L glass exposure chamber with a flow rate of 39 L/min so that the chamber concentration was rapidly equilibrated ( t , 28.5 s). The chamber equilibration time and stability s f the test material administration were monitored with an optical aerosol instrument (Sibata model P-5) and a strip chart recorder. Exposure concentrations were determined on both a nominal and actual basis. The nominal concentration was calculated by dividing the net weight loss of test material from the preweighed Wright Dust Feeder cup by the total volume of air passing through the chamber during exposure. The actual exposure concentration was determined gravimetrically. Timed air samples were drawn from the chamber during the exposure period, using a calibrated critical orifice and preweighed, 25-mm glass fiber filters. The filters were weighed again after sampling, and the aerosol concentration was calculated by dividing filter weight gain by the sample volume. At least two such samples were taken during each exposure. A bulk estimation technique was employed to characterize the particle size distribution of the test atmosphere. Particle size determinations of the test atmosphere were conducted during the exposure using a Sierra model 210 Cascade Impactor. Breweighed glass fiber filters were used to collect the aerosol on each stage. The change in weight of the filter for each stage was measured, and the cumulative percent of the sample collected on each stage was calculated. This information plus the stage constants for the impactor were used with the aid of a computer. fiperimefital design Animals were considered acceptable for testing on the basis of body weight (25-38 g) and general health. For each experiment, four mice were selected using a manually generated randomization method. The body of each mouse was held in a plethysmograph and inserted into the exposure chamber. The plethysmograph was sealed at one end with a rubber stopper, and at the other end with the head of the mouse, which extended into the exposure chamber. An airtight seal was provided by a rubber dam around the neck of the mouse. Each of the four plethysmographs of the mouse exposure chamber were connected to a pressure transducer. A positive pressure was created in the plethysmograph as each mouse inhaled; when the mouse exhaled, a negative pressure resulted. These pressure changes were sensed by pressure transducers, with the resulting signals amplified and displayed on an oscillograph. During inspiration, an upward deflection is observed on the oscillograph, and a downward deflection is observed during expiration. When an animal inhales a sensory irritant, the upward deflection remains normal, but a characteristic pause
4.
in the downward deflection occurs. This indicates that although the inspiration phase is unchanged, the animal holds its breath and therefore decreases the respiratory rate. Pulmonary or deep lung irritation typically increases the breathing frequency, and in most instances reduces the tidal volume. Breathing frequency was continuously recorded in both analog (oscillograph tracings) and digital (computer data file) forms for evaluation. Frequency data acquired for the computer file were obtained from electronic signals, which were sent from the oscillograph to a frequency analyzer, data logger, and a minicomputer. For the experiment, a control or pretest level was first established, during which the animals were exposed to fresh air for 10 min. This was followed by a 30-mirn exposure period to the sulfur dust aerosol. Aker the exposure period, the animals were monitored for an additional 5 - 10 min to measure recovery, during which animals breathed fresh air. For each animal, the percent decrease in respiratory rate from the control or pretest value was calculated during the exposure and recovery period. Group values represent the mean of four mice that were exposed to the same sulfur dust concentration.
Results As shown in Table 1, mice were exposed to 106, 263, or 451 rng/rn3 sulfur dust as ImXisu~ed by the gravimetric method. Nominal exposure concentrations were considerably higher, indicating that a substantial amount of the generated sulfur dust aerosol coated the surfaces of the generation system and exposure chamber, and thus was not airborne. At the highest exposure level, the concentration of 45 1 mg/m3 could only be achieved for the first 2% min. The generation system became obstructed with. the test material so that the concentration in the exposure chamber dropped to 51 mg/m3 for the last 8 min of the exposure period. The exact time of the drop in chamber concentration was determined from the recording of the on-line aerosol monitor. However, for the purposes of this study, this exposure concentration was considered to be 451 rng/rn3 and was thus the maximum concentration attainable with this generation system. The 50% mass median aerodynamic diameter (MMAD) of the aerosol ranged from 5.5 to 5.8 pm, and the percent of particles less than or equal to 10 prn ranged from 70 to 79% (Table I). These values indicated that the characteristics of the smlhr dust aerosol were similar for each of the exposure concentrations generated in this study. In addition, the particle size distribution showed that a significant portion of the sulhir dust aerosol was present as particles considered small enough to be inhaled and deposited at the target site, the nasal passages (Y. Alarie, personal communication). The response of the mice to sulfur dust is presented in Table 2. The onset of expsure was marked by an immediate animal reaction, indicating the response to the presence of the
Can. J. Physiol. Pharmacol. Downloaded from www.nrcresearchpress.com by San Diego (UCSD) on 01/08/15 For personal use only.
BRIEF REPORTS IRAPPORTS BREFS
test material. Exposure to 106 or 263 mg/m3 sulfur dust resulted in a response decrease of 7 and 17% , respectively. Since the breathing patterns of these mice appeared normal, with no apparent pause between inspiration and expiration (data not shown), the decrease in frequency did not reflect sensory irritation of the upper airway. At the highest exposure level (451 rng/m3), a slight increase in respiratory rate was observed. One mouse in this group had a 24% increase in respiratory rate and exhibited a breathing pattern indicative of pulmonary or deep lung irritation throughout the exposure period. The other three mice in this group showed normal breathing patterns. The eyes of all animals appeared normal during the exposure period. Upon removal from the chamber, two animals at 106 rng/m3 and three animals at 451 mg/m3 were observed with slight lacrimation. One day later, the eyes of aH mice appeared nsrmd.
The present study was the first quantitative investigation of the irritation potentid of sulfur dust. Exposure levels ranged from 10 to 45 times the Occupational Exposure Limit of the Alberta Government, which is 10 mg/m3, in an effort to generate a sensory irritation response. The average particle size, although larger than that considered respirable for mice, was considered small enough to be inhalable and to be deposited primarily in the nasal turbinates. Only a small p r tion of the sulfur dust was considered to have reached the Iower airway as a result of the filtering efficiency of the rodent nasal passages. This unique distribution of deposited particles was considered advantageous since the study was conducted to evaluate sensory irritation which is a phenomenon of the nasal passages. The decreases that were observed in breathing rates in the low- and mid-dose groups were within normal limits and were
not biologically significant. Furthermore, the animal breathing patterns were not indicative of sensory irritation. These results suggest that sulfur dust possesses little potential to stimulate the trigeminal nerve endings in the nasal passages to cause sensory irritation. Exposure to 452 mg/m3 sulfur dust resulted in one mouse exhibiting a change in breathing pattern that indicated deep lung, or pulmonary, irritation and resulted in a 24 % increase in breathing frequency. Given the 22-min exposure period and the high concentration of sulfur dust, it is plausible that a sufficient amount of sulfur dust reached the lower portions of the lung to produce an irritation response. Because sf the limitations of the test system, further investigation of the lower airway response may be needed.
The authors thank Mr. John Sigouriw for his technical assistance and Ms. Patricia Fellin for the preparation of the manuscript. This work was performed under contract for the Canadian Petroleum Association. Alarie, Y. 1966. Irritating properties of airborne materials to the upper respiratory tract. Arch. Environ. Health. 13: 433 -449. Alarie, Y. 1973. Sensory irritation by airborne chemicals. CRC Crit. Rev. Toxicol. 2: 299-363. Alarie, Y. 1981. Bioassay for evaluating the potency s f airborne sensory irritants and predicting acceptable levels of exposure in man. Food Css~net.Toxicol. 19: 623 -626. Cauna, N., Hinderer, K. H.,and Wentges, R. T. 1969. Sensory receptor organs of the human nasal respiratory mucosa. Am. J. Anat. 124: 189-209. Keele, C. A. 1962. The common chemical sense and its receptors. Arch. Int. Pharmacodyn. Ther. 139: 547 -557. National Institutes of Health. 1985. Guide for the care and use of laboratory animals. NIH Publication 85-23.
Effect of lithium chloride on ornithine decarboxylase activity in rat adrenal ALESSANDRA STRUMPFER, JERRYHSIAQ,BDPENG, A N D JAMES RHCHARDS~ Depanrneret of Bioehernistqy, University of British Columbia, Vancouver, B. C . , Canada V6T I W5
Received March 2, 1992 STRUMPFEW, A., HSIACB, J., PENG,T., and RICHARDS, J. 1992. Effect of lithium chloride on ornithine decarboxylase activity in rat adrenal. 78: 1293 - 1296. The effects of lithium chloride on ornithine decarboxylase (OBC) activity were compared in the adrenal and kidney of control (saline treated) and prolactin-treated rats. 8 B C activity was decreased in kidney of both groups of animals, the magnitude of the effect of lithium in the hormone-treat& group varying with the time of administering the lithium relative to prolactin. The response in the adrenal was quite different. Following treatment with LiC1, there was a gradual increase in ODC activity from a low of 18-35 pmol C 0 2 . 30 min-I . rng protein-' in control animals to values 28- to 38-fold greater at 5 h. In rats treated simultaneously with LiCI and prolactin, ODC activity was greater at 5 h than that observed in animals receiving either compound alone, indicating that their effects were additive. When LiCl was given 4 h after prolactin, i.e., 1 h before sacrifice, ODC activity decreased to a very Iow level at 5 h, as in other tissues. The increase in OBC activity in the adrenal following LiCl is of the same magnitude as the changes observed in tissues stimulated to undergo alterations in proliferation, differentiation, or metabolic or membrane activity by hormones and other external stimuli. Key words: ornithine decarboxylase, rat adrenal, effects of lithium.
'Author for correspondence. Printed in Canada 1 Irnprimt au Ca~ada
1293
Sensory irritation response in mice to sulfur dust C H R I S ~ P HBE E RVAN^
AND
FREDERICK T. WHITMAN
Can. J. Physiol. Pharmacol. Downloaded from www.nrcresearchpress.com by San Diego (UCSD) on 01/08/15 For personal use only.
Exxon Biomedical Sciences Inc., Mettlers R~cad,CN 2350, East Milbstone, N. J. 08875, U.S. A. Received April 88, 1992
BEVAN,C., and WHITMAN, FaT. 1992. Sensory irritation response in mice to sulfur dust. Can. J. Physiol. Bkarmacol. 70: 1291 - 1293. The potential of sulfur dust to produce sensory irritation was evaluated in mice. Male Swiss- Webster mice were exposed by head-only inhalation to 104, 263, or 458 mg/m3 sulfur dust aerosol at room temperature. Breathing frequency and patterns were monitored before, during, and after exposure to evaluate the animal's sensory irritation response to the test atmosphere. Group average breathing rates were decreased 7 and 17% below pretest values in mice exposed to 104 and 243 mg/m3, respectively; however, breathing patterns appeared normal, indicating that there was no sensory irritation. Mice exposed to 451 mg/m3 showed an increase in breathing frequency of 776, with 114 mice displaying very slight signs of pulmonary (deep lung) irritation. Some of the mice in the low- and high-dose groups exhibited signs of slight eye irritation immediately after exposure, but all mice were normal 1 day later. On the basis of these findings, exposure to sulfur dust up to 451 mg/m3 did not produce any sensory or upper airway irritation in mice. Key words: sensory irritation, sulfur dust, dust aerosol. BEVAN,C., et WHITMAN, E Te 1992. Sensory irritation response in mice to sulfur dust. Can. J . Physiol. Pharn~acol.70 : 1291 - 1293. On a CvaluC la capacitC de fines particules de soufre de provoquer une irritation sensorielle chez les souris. On a expos6 des ssuris Swiss-Webster males B 106, 263, ou 451 mg/m3 de poussikre de soufre en airosol, B temperature ambiante. On a enregistre la frtquence et les profils respiratoires avant, pendant et aprks l'exposition, pour Cvaluer la rCponse de 19irritation sensorielle des animaux ii lqatmosphbre-test. Ees taux respiratoires moyens des groaapes ont dirninue de 7 et de 17% au-dessous des valeurs pr6test chez les souris expostes il 106 et 263 mg/m3, respectivement; toutefois, les profils respiratoires ont sernblC normaux, indiquant B'absence d'irritation sensorielle. Les souris exposkes B 451 rng/m3 ont montre une augmentation de la frkqaaence respiratoire de 7 % , le 114 des souris pr6sentant de trks lCgers signes d'irritation pulmsnaire (poumon infbrieur). Quelques souris des groaapes avec dose faible et dose forte ont prksentt des signes de ICgkre irritation oculaire imm6diatement aprks l'exgosition, mais celle-ci avait dispam le lendemain. D'aprks ces rbsultats, une exposition A plus de 451 mg/m3 de poussikre de soufre n'a provoqub ni irritation des voies aeriennes supCrieures ni irritation sensorielle chez les souris. Mots clds : irritation sensorielle, poussikre de soufre, poussikre en abrosol. [Tradeait par la rddaction]
The Provincial Government of Alberta has set the occupational exposure limit for sulfur dust at 16 mg/m3 on the assumption that sulfur dust is a nuisance dust with no intrinsic tcexicologicd properties. Because little is known about the irritating properties of sulfur dust, the potential s f sulfur dust to produce an upper airway or sensory irritation response was investigated. The test system that. was chosen for the present study was an Alarie test (Alarie 1966), which measures the ability of a chemical to activate the trigerninal nerve endings in the nasal passages (Meele 1962; Cauna et a&.1969). A sensory irritant, when inhaled via the nose, will stimulate the trigeminal nerves, evoking a painful burning sensation of the nose and throat. In an acute exposure, this stimulation occurs in the absence of any histological damage to the nasal epithelium. The Alarie test has been validated for a wide range of gaseous and liquid aerosol irritants, covering a broad range of exposure concentrations and particle sizes (Marie 1993, 1981). The model involves two respiratory parameters: breathing pattern and frequency. The breathing pattern identifies whether the irritation is an upper airway response or a 'Author for correspondence. Printed in C a n d a 1 Imprim6 au Canada
lower (pulmonary) response, and the breathing frequency is used to measure the sensory irritation response. The decrease in breathing frequency observed with sensory irritants has been shown to be concentration dependent and can be quantitated to yield the RD5() (the exposure concentration that reduces the breathing frequency by 50%). The present study has characterized the type and degree sf change in respiratory behavior at sulfur dust concentrations in the range 100450 rng/m3.
Materials and methods Aazimals Male Swiss -Webster mice were supplied by Charles River B r e d ing Eaboratgbries (Portage, Michigan) and were approximately 6-7 weeks of age at the time of the study. Animals were housed individually in elevated, stainless steel wire mesh cages and maintained on a 12 h light : 12 h dark cycle. Animals were maintained and monitored in accordance with the Guide for the Care and Use of h b o r ~ t o r y Animals (1985). Food ( h r i n a 5002) and tap water were provided ad libitum. Room temperature and humidity were maintained at a range from 22 to 24'C and 41 to 69% respectively. '@,
Aerosol generation and exposure measurements Solid sulfur in the form of yellow pellets or chunks was obtained through the Canadian Petroleum Association. The test mterial was composed of a mixture of samples from each of the participating com-
CAN. J. PHYSIOL. PHAWMACOL. VOL. 70, 1992
1292
TABLE 2. Sensory irritation response of mice to sulfur dust aerosol
TABLE1. Characterization of the sulfur dust aerosol Sulfur dust exposure group Low Nominal chamber concn. (rng/rn3)"
Can. J. Physiol. Pharmacol. Downloaded from www.nrcresearchpress.com by San Diego (UCSD) on 01/08/15 For personal use only.
Actual chamber concn. (rnglrn")"
Middle
1205
2410
106
263
Response ($6 of control values)
High 3359 451"
Exposure (mfdm')
Exposure period
Recovery period
Particle sizea 50% size (pm) Geometric SD NOTE:Values represent the mean f SD, ?= l
"Value represents a single sample. b ~ a l u represents e the mean of two samples.
panies and was comidered to be representative of current production, taken directly after the sulfur-forming operation or from the sulfur pit. Solid sulfur was hand ground with a mortar and pestle at room temperamre and passed through a 60-mesh sieve. The dust was compressed and made airborne using a Wright Dust Feeder, which expelled the dust aerosol into a glass premixing vessel. The dust aerosol was then delivered into an -4-L glass exposure chamber with a flow rate of 39 L/min so that the chamber concentration was rapidly equilibrated ( t , 28.5 s). The chamber equilibration time and stability s f the test material administration were monitored with an optical aerosol instrument (Sibata model P-5) and a strip chart recorder. Exposure concentrations were determined on both a nominal and actual basis. The nominal concentration was calculated by dividing the net weight loss of test material from the preweighed Wright Dust Feeder cup by the total volume of air passing through the chamber during exposure. The actual exposure concentration was determined gravimetrically. Timed air samples were drawn from the chamber during the exposure period, using a calibrated critical orifice and preweighed, 25-mm glass fiber filters. The filters were weighed again after sampling, and the aerosol concentration was calculated by dividing filter weight gain by the sample volume. At least two such samples were taken during each exposure. A bulk estimation technique was employed to characterize the particle size distribution of the test atmosphere. Particle size determinations of the test atmosphere were conducted during the exposure using a Sierra model 210 Cascade Impactor. Breweighed glass fiber filters were used to collect the aerosol on each stage. The change in weight of the filter for each stage was measured, and the cumulative percent of the sample collected on each stage was calculated. This information plus the stage constants for the impactor were used with the aid of a computer. fiperimefital design Animals were considered acceptable for testing on the basis of body weight (25-38 g) and general health. For each experiment, four mice were selected using a manually generated randomization method. The body of each mouse was held in a plethysmograph and inserted into the exposure chamber. The plethysmograph was sealed at one end with a rubber stopper, and at the other end with the head of the mouse, which extended into the exposure chamber. An airtight seal was provided by a rubber dam around the neck of the mouse. Each of the four plethysmographs of the mouse exposure chamber were connected to a pressure transducer. A positive pressure was created in the plethysmograph as each mouse inhaled; when the mouse exhaled, a negative pressure resulted. These pressure changes were sensed by pressure transducers, with the resulting signals amplified and displayed on an oscillograph. During inspiration, an upward deflection is observed on the oscillograph, and a downward deflection is observed during expiration. When an animal inhales a sensory irritant, the upward deflection remains normal, but a characteristic pause
4.
in the downward deflection occurs. This indicates that although the inspiration phase is unchanged, the animal holds its breath and therefore decreases the respiratory rate. Pulmonary or deep lung irritation typically increases the breathing frequency, and in most instances reduces the tidal volume. Breathing frequency was continuously recorded in both analog (oscillograph tracings) and digital (computer data file) forms for evaluation. Frequency data acquired for the computer file were obtained from electronic signals, which were sent from the oscillograph to a frequency analyzer, data logger, and a minicomputer. For the experiment, a control or pretest level was first established, during which the animals were exposed to fresh air for 10 min. This was followed by a 30-mirn exposure period to the sulfur dust aerosol. Aker the exposure period, the animals were monitored for an additional 5 - 10 min to measure recovery, during which animals breathed fresh air. For each animal, the percent decrease in respiratory rate from the control or pretest value was calculated during the exposure and recovery period. Group values represent the mean of four mice that were exposed to the same sulfur dust concentration.
Results As shown in Table 1, mice were exposed to 106, 263, or 451 rng/rn3 sulfur dust as ImXisu~ed by the gravimetric method. Nominal exposure concentrations were considerably higher, indicating that a substantial amount of the generated sulfur dust aerosol coated the surfaces of the generation system and exposure chamber, and thus was not airborne. At the highest exposure level, the concentration of 45 1 mg/m3 could only be achieved for the first 2% min. The generation system became obstructed with. the test material so that the concentration in the exposure chamber dropped to 51 mg/m3 for the last 8 min of the exposure period. The exact time of the drop in chamber concentration was determined from the recording of the on-line aerosol monitor. However, for the purposes of this study, this exposure concentration was considered to be 451 rng/rn3 and was thus the maximum concentration attainable with this generation system. The 50% mass median aerodynamic diameter (MMAD) of the aerosol ranged from 5.5 to 5.8 pm, and the percent of particles less than or equal to 10 prn ranged from 70 to 79% (Table I). These values indicated that the characteristics of the smlhr dust aerosol were similar for each of the exposure concentrations generated in this study. In addition, the particle size distribution showed that a significant portion of the sulhir dust aerosol was present as particles considered small enough to be inhaled and deposited at the target site, the nasal passages (Y. Alarie, personal communication). The response of the mice to sulfur dust is presented in Table 2. The onset of expsure was marked by an immediate animal reaction, indicating the response to the presence of the
Can. J. Physiol. Pharmacol. Downloaded from www.nrcresearchpress.com by San Diego (UCSD) on 01/08/15 For personal use only.
BRIEF REPORTS IRAPPORTS BREFS
test material. Exposure to 106 or 263 mg/m3 sulfur dust resulted in a response decrease of 7 and 17% , respectively. Since the breathing patterns of these mice appeared normal, with no apparent pause between inspiration and expiration (data not shown), the decrease in frequency did not reflect sensory irritation of the upper airway. At the highest exposure level (451 rng/m3), a slight increase in respiratory rate was observed. One mouse in this group had a 24% increase in respiratory rate and exhibited a breathing pattern indicative of pulmonary or deep lung irritation throughout the exposure period. The other three mice in this group showed normal breathing patterns. The eyes of all animals appeared normal during the exposure period. Upon removal from the chamber, two animals at 106 rng/m3 and three animals at 451 mg/m3 were observed with slight lacrimation. One day later, the eyes of aH mice appeared nsrmd.
The present study was the first quantitative investigation of the irritation potentid of sulfur dust. Exposure levels ranged from 10 to 45 times the Occupational Exposure Limit of the Alberta Government, which is 10 mg/m3, in an effort to generate a sensory irritation response. The average particle size, although larger than that considered respirable for mice, was considered small enough to be inhalable and to be deposited primarily in the nasal turbinates. Only a small p r tion of the sulfur dust was considered to have reached the Iower airway as a result of the filtering efficiency of the rodent nasal passages. This unique distribution of deposited particles was considered advantageous since the study was conducted to evaluate sensory irritation which is a phenomenon of the nasal passages. The decreases that were observed in breathing rates in the low- and mid-dose groups were within normal limits and were
not biologically significant. Furthermore, the animal breathing patterns were not indicative of sensory irritation. These results suggest that sulfur dust possesses little potential to stimulate the trigeminal nerve endings in the nasal passages to cause sensory irritation. Exposure to 452 mg/m3 sulfur dust resulted in one mouse exhibiting a change in breathing pattern that indicated deep lung, or pulmonary, irritation and resulted in a 24 % increase in breathing frequency. Given the 22-min exposure period and the high concentration of sulfur dust, it is plausible that a sufficient amount of sulfur dust reached the lower portions of the lung to produce an irritation response. Because sf the limitations of the test system, further investigation of the lower airway response may be needed.
The authors thank Mr. John Sigouriw for his technical assistance and Ms. Patricia Fellin for the preparation of the manuscript. This work was performed under contract for the Canadian Petroleum Association. Alarie, Y. 1966. Irritating properties of airborne materials to the upper respiratory tract. Arch. Environ. Health. 13: 433 -449. Alarie, Y. 1973. Sensory irritation by airborne chemicals. CRC Crit. Rev. Toxicol. 2: 299-363. Alarie, Y. 1981. Bioassay for evaluating the potency s f airborne sensory irritants and predicting acceptable levels of exposure in man. Food Css~net.Toxicol. 19: 623 -626. Cauna, N., Hinderer, K. H.,and Wentges, R. T. 1969. Sensory receptor organs of the human nasal respiratory mucosa. Am. J. Anat. 124: 189-209. Keele, C. A. 1962. The common chemical sense and its receptors. Arch. Int. Pharmacodyn. Ther. 139: 547 -557. National Institutes of Health. 1985. Guide for the care and use of laboratory animals. NIH Publication 85-23.
Effect of lithium chloride on ornithine decarboxylase activity in rat adrenal ALESSANDRA STRUMPFER, JERRYHSIAQ,BDPENG, A N D JAMES RHCHARDS~ Depanrneret of Bioehernistqy, University of British Columbia, Vancouver, B. C . , Canada V6T I W5
Received March 2, 1992 STRUMPFEW, A., HSIACB, J., PENG,T., and RICHARDS, J. 1992. Effect of lithium chloride on ornithine decarboxylase activity in rat adrenal. 78: 1293 - 1296. The effects of lithium chloride on ornithine decarboxylase (OBC) activity were compared in the adrenal and kidney of control (saline treated) and prolactin-treated rats. 8 B C activity was decreased in kidney of both groups of animals, the magnitude of the effect of lithium in the hormone-treat& group varying with the time of administering the lithium relative to prolactin. The response in the adrenal was quite different. Following treatment with LiC1, there was a gradual increase in ODC activity from a low of 18-35 pmol C 0 2 . 30 min-I . rng protein-' in control animals to values 28- to 38-fold greater at 5 h. In rats treated simultaneously with LiCI and prolactin, ODC activity was greater at 5 h than that observed in animals receiving either compound alone, indicating that their effects were additive. When LiCl was given 4 h after prolactin, i.e., 1 h before sacrifice, ODC activity decreased to a very Iow level at 5 h, as in other tissues. The increase in OBC activity in the adrenal following LiCl is of the same magnitude as the changes observed in tissues stimulated to undergo alterations in proliferation, differentiation, or metabolic or membrane activity by hormones and other external stimuli. Key words: ornithine decarboxylase, rat adrenal, effects of lithium.
'Author for correspondence. Printed in Canada 1 Irnprimt au Ca~ada
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