Pfli.igers Archiv
Pfl/igers Arch. 370, 287-289 (5977)
EuropeanJoun',al of Physiology 9 by Springer-Verlag 1977
Physiological Responses of Dogs on Exposure to Hot, Arid Conditions Serum Constituents STEPHEN KRAUSZ 1, JACOB MARDER 1, and URI EYLATH 2 1 Department of Zoology, The Hebrew University, Jerusalem 2 Clinical Laboratory, Shaare Zedek General Hospital, Jerusalem, Israel
Summary. Serum electrolytes, metabolites and enzymes were determined in arterial blood of chronically cannulated dogs at room temperature and on exposure to 4 4 - 5 0 ~C. These dogs were naturally acclimated to hot, arid conditions. In dogs maintaining their rectal temperatures (TR) below 40 ~C, no significant changes were seen in the levels of Na § C1-, cholesterol, uric acid, alkaline phosphatase, lactic dehydrogenase or glutamic-pyruvic transaminase (SGPT). K § CO2, glucose decreased significantly, and urea nitrogen (BUN) and glutamic-oxaloacetic transaminase (SGOT) showed small but significant increases. In several cases of excitable dogs, in which TR increased above 40 ~ C, we found large, significant increases in uric acid, SGPT and SGOT, and a decrease in cholesterol. The results suggest that in dogs maintaining their T~ when exposed to high temperatures, changes in serum constituents indicate merely the presence of respiratory alkalosis and an increased energetic demand. When control of TR is lost, changes occur which suggest liver, and possibly cardiac, tissue damage.
Key words: Hyperthermia - Serum electrolytes Serum enzymes.
creased Paco~ (arterial CO2 partial pressure) causes a decrease in cerebral blood flow, resulting in impairment of central nervous system regulation; the addition of CO2 to the inspired air maintains normal cerebral blood flow, and so prevents possible tissue damage. Body temperature is also maintained by the addition of CO2. In previous work [7] we have demonstrated the possibility of a group of dogs from a warm environment being naturally acclimated to hot, arid conditions, and responding to heat exposure with considerably less respiratory alkalosis than obtained by Albers et al. [1]: a pH of 7.538 + 0.017 and a Paco2 of 20.9 _ 1.2 torr at 47~ and 3 0 ~ relative humidity (R.H.) as opposed to 7 . 6 9 _ 0.063 and 10.2 __+ 3.8 at 40~ and 5 0 ~ R.H. We were interested in seeing whether, by virtue of reduced CO2 loss, such dogs were also able to maintain their serum enzyme levels. At the same time, as significant changes in electrolyte levels have been reported, by some authors during heat exposure [4], though not by some others [3, 6], and as metabolic expenditures are greatly increased [5, 12], we were interested in measuring electrolytes and several metabolites in order to examine the general metabolic response of dogs exposed to extremely hot, arid conditions.
INTRODUCTION
METHODS
Extreme increases in serum enzyme levels (SGOT, SGPT, ICDH) have been noted in dogs after extended exposure to hyperthermic conditions, suggesting liver, and perhaps cardiac, tissue damage [13]. Albers et al. [1] similarly obtained increases in LDH, SGOT, c~-HBDH and CPK (but not in SGPT) at 40 ~ C, but with the addition of 4 ~ CO2 to the inspired air, these increases were abolished. They suggest that de-
Four dogs, chronically cannulated in the carotid artery as described by Krausz and Marder [7] were studied. The dogs were individually housed in 3 m 2 cages while they had cannulae, fed standard dry dog food and water, ad lib., but were fasted overnight before experiments. Experiments took place in a temperature controlled room (accurate to _+ 0.1 ~ C; R.H. was maintained below 30~). Dogs were put in the room in the evening, at 25 ~C, arterial blood was sampled via the cannula in the morning, and they were then exposed in 3-h stages to 35, 40, 44, 47, and (in the case of one dog), 50~ C. A sample was taken at the highest temperature reached on any particular day (3 samples at 44 ~C, 10 samples at 47 ~C, and 2 samples at 50~ have been pooled in the statistical analysis). Blood was collected in non-heparinized evacuated test tubes.
Send offprint requests to: S. Krausz, Department of Anesthesiology, UCLA School of Medicine, Los Angeles, Cal. 90024, U.S.A.
288
Pflfigers Arch. 370 (1977)
Table 1. Summaryof autoanalyzermethodsused for determining serum constituents
alk. pH. rnU/ml
[ ] T room
Constituent
Method
Na +
flame photometry
K+
flame photometry
C1-
reaction with mercuric thiocyanate in presence of Fe 3+ to form Fe(SCN)3
C02
absorption in pH 10 buffer solution in presence of cresol red indicator
cholesterol
Liebermann-Buchard reagent
glucose
reduction of a cupric-neocuproine chelate
BUN
reaction with diacetyl-monoxime
uric acid
reduction of phosphotungstate
alkaline phosphatase
enzymatic hydrolysis of p-nitrophenyl phosphate
LDH
coupling of lactate oxidation to reduction of tetrazolium dye
SGPT
enzymatic synthesis of pyruvate; NADH is then oxidized by reducing pyruvate to lactate in presence of LDH
SGOT
enzymatic synthesis of oxaloacetate; NADH is then oxidized by reducing oxaloacetate to malate in the presence of MDH
Serum was separated and stored under refrigeration until assayed for concentrations of Na +, K +, CI-, CO2, glucose, cholesterol, urea nitrogen (BUN) and uric acid, and activities of alkaline phosphatase, lactic dehydrogenase (LDH), and glutamic-pyruvic and glutamic-oxaloacetic transaminases (SGPT and SGOT) by standard autoanalyzer techniques (summarized briefly in Table 1) on a Technicon Instruments (Tarrytown, NY) SMA 12/60. Results are reported as means • standard errors (S.E.M.), and the significance of results was determined using Student's "t" test
RESULTS The results are summarized in Figure 1. No significant changes were seen in the levels of Na +, CI-, cholesterol, uric acid, or the activities of alkaline phosphatase, LDH or SGPT, while significant decreases were seen in the levels o f K + (from 4.2 _+ 0.1 meq/1 to 3.6 • 0.2, P < 0.02), CO2 (from 19 • 1 to 14 __ I meq/1, P < 0.01) and glucose (from 96 • 3 to 69 • 6 mg %, P < 0.001), and significant increases in the levels of BUN (from 1 2 _ 1 to 15 • l m g % , P < 0.05) and SGOT (from 28 • 2 to 36 • 2 mU/ml, P < 0.01). DISCUSSION Our room temperature results are consistent with values generally reported for dogs [8-10]. In the heat we found no significant changes in Na + or CI-
[]
4 4 - 50~
Na ~
CO2 meq/I
glucose mg~
LDH ml
BUN rag% urm. acid
~
SGOT SGPT rnU/rnl mU/ml
Fig. 1. Serum constituents at room temperature (25 ~C) and in the heat ( 4 4 - 5 0 ~C) in four dogs. Results are drawn as means + S.E.M. (n = 13 at 25~ 15 at 4 4 - 5 0 ~
concentrations. Thus, there is no indication of hemodilution, a response generally seen in man exposed to heat [11]; hematocrit also showed no significant change, being 42 4- 1 ~ at 25~ and 41 +_ 1 ~ at 47~ (unpublished observation). No change in electrolyte levels have been reported by others [3, 6]. K § concentration, on the other hand, decreased significantly. This is probably a consequence of the redistribution o f K § accompanying the decreased plasma [HCO~-]. Kanter [4] found increased K + excretion in the urine accompanying bicarbonate output in heat exposed dogs, which he suggests is an effort to offset respiratory alkalosis. The decrease observed in glucose concentration conforms to the results of Kanter [5], and apparently results from increased glucose utilization by respiratory muscles in panting. The increased BUN and SGOT accompanying the glucose decrease suggest an increase in gluconeogenesis from proteins due to these increased metabolic demands. The SGOT increase may also be a consequence of increased cardiac output. Increases in serum enzyme activities during heat stress have already been noted, apparently due to increased cellular permeability [2]. Spurr [13] has suggested that repeated hyperthermic exposure in dogs results in enzyme changes which suggest damage to liver, and perhaps cardiac, tissue. In repeated exposures to high temperatures in our dogs, we did not find such increases in LDH or SGPT, and the increase in SGOT was much smaller than he found. It should be pointed out, however, that our dogs responded to increased TA with only a small increase in body temperature (from 38.1 • 0.1~ at 25~ TA to 39.4 • 0.2~ at 47~ TA). On eight occasions, during a variety of experi-
S. Krausz et al. : Serum Constituents of Heat-Exposed Dogs
mental procedures, we were able to take blood samples from dogs who, due to excitement, exhibited body temperatures above 40.0 ~ C. On these occasions, we found a significant decrease in cholesterol levels (from 213_+ 12 to 161 + 1 l i n g O , P < 0.01) significant increases in uric acid (from 0.6 __ 0.1 to 1.6 +_ 0.3 m g ~ , P < 0 . 0 1 ) , SGPT (from 32 _ 4 to 67 _+ 10mU/ml, P < 0 . 0 1 ) , and SGOT (from 28 _+ 2 to 109 _+ 31 mU/ml, P < 0.02). LDH increased greatly in several cases, but was highly variable, and so did not show a statistically significant increase (from 162 + 10 to 273 _+ 56 mU/ml, P > 0.05). These changes are consistent with tissue damage [13], and suggest that increased body temperature, rather than increased metabolic activity, is the prime cause of increased serum enzymes during heat exposure. Albers et al. [1] also obtained increased LDH and SGOT (but not SGPT) activity on exposure of dogs to 40~ and 50 ~o R.H., increases which were eliminated by the addition of 4 ~ CO2 to the inspired air. The CO2 also reduced the TR increase otherwise obtained. They suggest that it is the reduced Paco~ that, via decreased cerebral blood flow, leads to CNS dysfunction, and that "prevention of the alkalosis by increasing the inspiratory CO2 concentration inhibits the functional disturbances and the increase in plasma enzyme levels". Our results with a group of dogs which limit their Paco2 decrease during exposure to hot, arid conditions [7], support the idea that a reasonable regulation of body temperature and Paco2 inhibits serum enzyme changes, and allows minimal metabolic disturbance during exposure to high environmental temperatures.
289
REFERENCES i. Albers, C., Usinger, W., Scholand, C.: Intracellular pH in unanesthetized dogs during panting. Respir. Physiol. 23, 59-70 (1975) 2. Bedrak, E.: Blood serum enzyme activity of dogs exposed to heat stress and muscular exercise. J. Appl. Physiol. 20, 587590 (1965) 3. Harrison, M. H. : Plasma volume changes during acute exposure to a high environmental temperature. J. Appl. Physiol. 37, 38-42 (1974) 4. Kanter, G. S. : Effect of heat on regulation of body fluids and electrolytes in dogs. Am. J. Physiol. 178, 259-262 (1954) 5. Kanter, G. S.: Cause of hypoglycemia in dogs exposed to heat. Am. J. Physiol. 196, 619-624 (1959) 6. Kappey, F. : Die Ausl6sung des W/irmehechelns beim Hund bei experimentell erzeugter metabolischer Acidose und Alkalose. Pfltigers Arch. 276, 18 - 31 (1962) 7. Krausz, S., Marder, J.: Physiological responses of dogs on exposure to hot, arid conditions. Acid-base status. Pfliigers Arch. 370, 283-286 (1977) 8. Lane, D. R., Robinson, R. : The utility of biochemical screening in dogs. I. Normal ranges. Brit. Vet. J. 126, 230-237 (1970) 9. Pickrell, J.A., Schluter, S.J., Belasich, J.J., Stewart, E. V., Meyer, J., Hobbs, C. H., Jones, R. K, : Relationship of age of normal dogs to blood serum constituents and reliability of measured single values. Am. J. Vet. Res. 35, 897-903 (1974) 10. Secord, D. C., Russell, J. C.: A clinical laboratory study of conditioned mongrel dogs and Labrador retrievers. Lab. Anita. Sci. 23, 567-571 (1973) i1. Senay, L. C., Jr.: Plasma volumes and constituents of heatexposed men before and after acclimatization. J. Appl. Physiol. 38, 570-575 (1975) 12. Spaich, P., Usinger, W., Albers, C.: Oxygen cost of panting in anesthetized dogs. Respir. Physiol. 5, 302-314 (1968) 13. Spurr, G. B.: Serum enzymes following repetitive hyperthermia. Proc. Soc. Exper. Biol. Med. 139, 698-700 (1972)
Received March 2, 1977
Pfl/igers Arch. 370, 287-289 (5977)
EuropeanJoun',al of Physiology 9 by Springer-Verlag 1977
Physiological Responses of Dogs on Exposure to Hot, Arid Conditions Serum Constituents STEPHEN KRAUSZ 1, JACOB MARDER 1, and URI EYLATH 2 1 Department of Zoology, The Hebrew University, Jerusalem 2 Clinical Laboratory, Shaare Zedek General Hospital, Jerusalem, Israel
Summary. Serum electrolytes, metabolites and enzymes were determined in arterial blood of chronically cannulated dogs at room temperature and on exposure to 4 4 - 5 0 ~C. These dogs were naturally acclimated to hot, arid conditions. In dogs maintaining their rectal temperatures (TR) below 40 ~C, no significant changes were seen in the levels of Na § C1-, cholesterol, uric acid, alkaline phosphatase, lactic dehydrogenase or glutamic-pyruvic transaminase (SGPT). K § CO2, glucose decreased significantly, and urea nitrogen (BUN) and glutamic-oxaloacetic transaminase (SGOT) showed small but significant increases. In several cases of excitable dogs, in which TR increased above 40 ~ C, we found large, significant increases in uric acid, SGPT and SGOT, and a decrease in cholesterol. The results suggest that in dogs maintaining their T~ when exposed to high temperatures, changes in serum constituents indicate merely the presence of respiratory alkalosis and an increased energetic demand. When control of TR is lost, changes occur which suggest liver, and possibly cardiac, tissue damage.
Key words: Hyperthermia - Serum electrolytes Serum enzymes.
creased Paco~ (arterial CO2 partial pressure) causes a decrease in cerebral blood flow, resulting in impairment of central nervous system regulation; the addition of CO2 to the inspired air maintains normal cerebral blood flow, and so prevents possible tissue damage. Body temperature is also maintained by the addition of CO2. In previous work [7] we have demonstrated the possibility of a group of dogs from a warm environment being naturally acclimated to hot, arid conditions, and responding to heat exposure with considerably less respiratory alkalosis than obtained by Albers et al. [1]: a pH of 7.538 + 0.017 and a Paco2 of 20.9 _ 1.2 torr at 47~ and 3 0 ~ relative humidity (R.H.) as opposed to 7 . 6 9 _ 0.063 and 10.2 __+ 3.8 at 40~ and 5 0 ~ R.H. We were interested in seeing whether, by virtue of reduced CO2 loss, such dogs were also able to maintain their serum enzyme levels. At the same time, as significant changes in electrolyte levels have been reported, by some authors during heat exposure [4], though not by some others [3, 6], and as metabolic expenditures are greatly increased [5, 12], we were interested in measuring electrolytes and several metabolites in order to examine the general metabolic response of dogs exposed to extremely hot, arid conditions.
INTRODUCTION
METHODS
Extreme increases in serum enzyme levels (SGOT, SGPT, ICDH) have been noted in dogs after extended exposure to hyperthermic conditions, suggesting liver, and perhaps cardiac, tissue damage [13]. Albers et al. [1] similarly obtained increases in LDH, SGOT, c~-HBDH and CPK (but not in SGPT) at 40 ~ C, but with the addition of 4 ~ CO2 to the inspired air, these increases were abolished. They suggest that de-
Four dogs, chronically cannulated in the carotid artery as described by Krausz and Marder [7] were studied. The dogs were individually housed in 3 m 2 cages while they had cannulae, fed standard dry dog food and water, ad lib., but were fasted overnight before experiments. Experiments took place in a temperature controlled room (accurate to _+ 0.1 ~ C; R.H. was maintained below 30~). Dogs were put in the room in the evening, at 25 ~C, arterial blood was sampled via the cannula in the morning, and they were then exposed in 3-h stages to 35, 40, 44, 47, and (in the case of one dog), 50~ C. A sample was taken at the highest temperature reached on any particular day (3 samples at 44 ~C, 10 samples at 47 ~C, and 2 samples at 50~ have been pooled in the statistical analysis). Blood was collected in non-heparinized evacuated test tubes.
Send offprint requests to: S. Krausz, Department of Anesthesiology, UCLA School of Medicine, Los Angeles, Cal. 90024, U.S.A.
288
Pflfigers Arch. 370 (1977)
Table 1. Summaryof autoanalyzermethodsused for determining serum constituents
alk. pH. rnU/ml
[ ] T room
Constituent
Method
Na +
flame photometry
K+
flame photometry
C1-
reaction with mercuric thiocyanate in presence of Fe 3+ to form Fe(SCN)3
C02
absorption in pH 10 buffer solution in presence of cresol red indicator
cholesterol
Liebermann-Buchard reagent
glucose
reduction of a cupric-neocuproine chelate
BUN
reaction with diacetyl-monoxime
uric acid
reduction of phosphotungstate
alkaline phosphatase
enzymatic hydrolysis of p-nitrophenyl phosphate
LDH
coupling of lactate oxidation to reduction of tetrazolium dye
SGPT
enzymatic synthesis of pyruvate; NADH is then oxidized by reducing pyruvate to lactate in presence of LDH
SGOT
enzymatic synthesis of oxaloacetate; NADH is then oxidized by reducing oxaloacetate to malate in the presence of MDH
Serum was separated and stored under refrigeration until assayed for concentrations of Na +, K +, CI-, CO2, glucose, cholesterol, urea nitrogen (BUN) and uric acid, and activities of alkaline phosphatase, lactic dehydrogenase (LDH), and glutamic-pyruvic and glutamic-oxaloacetic transaminases (SGPT and SGOT) by standard autoanalyzer techniques (summarized briefly in Table 1) on a Technicon Instruments (Tarrytown, NY) SMA 12/60. Results are reported as means • standard errors (S.E.M.), and the significance of results was determined using Student's "t" test
RESULTS The results are summarized in Figure 1. No significant changes were seen in the levels of Na +, CI-, cholesterol, uric acid, or the activities of alkaline phosphatase, LDH or SGPT, while significant decreases were seen in the levels o f K + (from 4.2 _+ 0.1 meq/1 to 3.6 • 0.2, P < 0.02), CO2 (from 19 • 1 to 14 __ I meq/1, P < 0.01) and glucose (from 96 • 3 to 69 • 6 mg %, P < 0.001), and significant increases in the levels of BUN (from 1 2 _ 1 to 15 • l m g % , P < 0.05) and SGOT (from 28 • 2 to 36 • 2 mU/ml, P < 0.01). DISCUSSION Our room temperature results are consistent with values generally reported for dogs [8-10]. In the heat we found no significant changes in Na + or CI-
[]
4 4 - 50~
Na ~
CO2 meq/I
glucose mg~
LDH ml
BUN rag% urm. acid
~
SGOT SGPT rnU/rnl mU/ml
Fig. 1. Serum constituents at room temperature (25 ~C) and in the heat ( 4 4 - 5 0 ~C) in four dogs. Results are drawn as means + S.E.M. (n = 13 at 25~ 15 at 4 4 - 5 0 ~
concentrations. Thus, there is no indication of hemodilution, a response generally seen in man exposed to heat [11]; hematocrit also showed no significant change, being 42 4- 1 ~ at 25~ and 41 +_ 1 ~ at 47~ (unpublished observation). No change in electrolyte levels have been reported by others [3, 6]. K § concentration, on the other hand, decreased significantly. This is probably a consequence of the redistribution o f K § accompanying the decreased plasma [HCO~-]. Kanter [4] found increased K + excretion in the urine accompanying bicarbonate output in heat exposed dogs, which he suggests is an effort to offset respiratory alkalosis. The decrease observed in glucose concentration conforms to the results of Kanter [5], and apparently results from increased glucose utilization by respiratory muscles in panting. The increased BUN and SGOT accompanying the glucose decrease suggest an increase in gluconeogenesis from proteins due to these increased metabolic demands. The SGOT increase may also be a consequence of increased cardiac output. Increases in serum enzyme activities during heat stress have already been noted, apparently due to increased cellular permeability [2]. Spurr [13] has suggested that repeated hyperthermic exposure in dogs results in enzyme changes which suggest damage to liver, and perhaps cardiac, tissue. In repeated exposures to high temperatures in our dogs, we did not find such increases in LDH or SGPT, and the increase in SGOT was much smaller than he found. It should be pointed out, however, that our dogs responded to increased TA with only a small increase in body temperature (from 38.1 • 0.1~ at 25~ TA to 39.4 • 0.2~ at 47~ TA). On eight occasions, during a variety of experi-
S. Krausz et al. : Serum Constituents of Heat-Exposed Dogs
mental procedures, we were able to take blood samples from dogs who, due to excitement, exhibited body temperatures above 40.0 ~ C. On these occasions, we found a significant decrease in cholesterol levels (from 213_+ 12 to 161 + 1 l i n g O , P < 0.01) significant increases in uric acid (from 0.6 __ 0.1 to 1.6 +_ 0.3 m g ~ , P < 0 . 0 1 ) , SGPT (from 32 _ 4 to 67 _+ 10mU/ml, P < 0 . 0 1 ) , and SGOT (from 28 _+ 2 to 109 _+ 31 mU/ml, P < 0.02). LDH increased greatly in several cases, but was highly variable, and so did not show a statistically significant increase (from 162 + 10 to 273 _+ 56 mU/ml, P > 0.05). These changes are consistent with tissue damage [13], and suggest that increased body temperature, rather than increased metabolic activity, is the prime cause of increased serum enzymes during heat exposure. Albers et al. [1] also obtained increased LDH and SGOT (but not SGPT) activity on exposure of dogs to 40~ and 50 ~o R.H., increases which were eliminated by the addition of 4 ~ CO2 to the inspired air. The CO2 also reduced the TR increase otherwise obtained. They suggest that it is the reduced Paco~ that, via decreased cerebral blood flow, leads to CNS dysfunction, and that "prevention of the alkalosis by increasing the inspiratory CO2 concentration inhibits the functional disturbances and the increase in plasma enzyme levels". Our results with a group of dogs which limit their Paco2 decrease during exposure to hot, arid conditions [7], support the idea that a reasonable regulation of body temperature and Paco2 inhibits serum enzyme changes, and allows minimal metabolic disturbance during exposure to high environmental temperatures.
289
REFERENCES i. Albers, C., Usinger, W., Scholand, C.: Intracellular pH in unanesthetized dogs during panting. Respir. Physiol. 23, 59-70 (1975) 2. Bedrak, E.: Blood serum enzyme activity of dogs exposed to heat stress and muscular exercise. J. Appl. Physiol. 20, 587590 (1965) 3. Harrison, M. H. : Plasma volume changes during acute exposure to a high environmental temperature. J. Appl. Physiol. 37, 38-42 (1974) 4. Kanter, G. S. : Effect of heat on regulation of body fluids and electrolytes in dogs. Am. J. Physiol. 178, 259-262 (1954) 5. Kanter, G. S.: Cause of hypoglycemia in dogs exposed to heat. Am. J. Physiol. 196, 619-624 (1959) 6. Kappey, F. : Die Ausl6sung des W/irmehechelns beim Hund bei experimentell erzeugter metabolischer Acidose und Alkalose. Pfltigers Arch. 276, 18 - 31 (1962) 7. Krausz, S., Marder, J.: Physiological responses of dogs on exposure to hot, arid conditions. Acid-base status. Pfliigers Arch. 370, 283-286 (1977) 8. Lane, D. R., Robinson, R. : The utility of biochemical screening in dogs. I. Normal ranges. Brit. Vet. J. 126, 230-237 (1970) 9. Pickrell, J.A., Schluter, S.J., Belasich, J.J., Stewart, E. V., Meyer, J., Hobbs, C. H., Jones, R. K, : Relationship of age of normal dogs to blood serum constituents and reliability of measured single values. Am. J. Vet. Res. 35, 897-903 (1974) 10. Secord, D. C., Russell, J. C.: A clinical laboratory study of conditioned mongrel dogs and Labrador retrievers. Lab. Anita. Sci. 23, 567-571 (1973) i1. Senay, L. C., Jr.: Plasma volumes and constituents of heatexposed men before and after acclimatization. J. Appl. Physiol. 38, 570-575 (1975) 12. Spaich, P., Usinger, W., Albers, C.: Oxygen cost of panting in anesthetized dogs. Respir. Physiol. 5, 302-314 (1968) 13. Spurr, G. B.: Serum enzymes following repetitive hyperthermia. Proc. Soc. Exper. Biol. Med. 139, 698-700 (1972)
Received March 2, 1977
