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Archives of Environmental Health: An International Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vzeh20
Lead, Zinc, and Erythrocyte δ-Aminolevulinic Acid Dehydratase: Relationships in Lead Toxicity a
a
a
a
a
Joseph A. Thomasino M. D. , Edward Zuroweste , Stuart M. Brooks M. D. , Harold G. Petering Ph. D. , Sidney I. Lerner M. D. & Vincent N. Finelli Ph. D.
a
a
Department of Environmental Health , University of Cincinnati College of Medicine Published online: 16 Apr 2013.
To cite this article: Joseph A. Thomasino M. D. , Edward Zuroweste , Stuart M. Brooks M. D. , Harold G. Petering Ph. D. , Sidney I. Lerner M. D. & Vincent N. Finelli Ph. D. (1977) Lead, Zinc, and Erythrocyte δ-Aminolevulinic Acid Dehydratase: Relationships in Lead Toxicity, Archives of Environmental Health: An International Journal, 32:6, 244-247, DOI: 10.1080/00039896.1977.10667290 To link to this article: http://dx.doi.org/10.1080/00039896.1977.10667290
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
Lead, Zinc, inc, and Erythrocyte rythrocyte minolevulinic Acid cid ^®kpiratase ehy atase:: Aminolevulinic .. Relationships Tcxicity el ons . ps in Lead Tomei
Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 22:15 25 December 2014
ة-
JOSEPH A. THOMASINO, M. D. EDWARD ZUROWESTE STUART M. BROOKS, M. D. HAROLD G. PETERING, Ph. D. SIDNEY I. LERNER, M. D. VINCENT N. FINELLI, Ph. D. DepaJrtment of Environmentall Heallth University of Cincinnati College of Medicine ABSTRACT A lead-intoxicated patient with extremely Jrigh blood lead levels and unexpectedly mild symptoms was studied priOl to and following treatment with callcium disodium edetate (ethyleneaiammetetrrultcetic add) and then priOl: to:rnd following mall administration of zinc swiate. During chelation therapy, exytluocyte (o)-aminolewlinic acid dehydratase (ALAn) activity decreased as blood lead levels fell.. UrinaJrY excretion of zinc increased and was more than 3.5 times greater than ilia! of lead. The ratio of blood lead to serum zinc was greatest (1.47) when ALAD activity was lowest. Orall administration of zinc sweate following chelation therapy resulted in a significant increase in mean ALAD actiVlity. In Vlitro additions of zinc chloride to the patient's erylli.rocytes resulted in reactivation of ALAD activity. These studies suggest iliat zinc is an important element in the ALAn system in man. Zinc may playa protective roie in lead toXlicity, and zinc supplementation may be a useful adjull.ct to chelation therapy for lead toXlicity.
LEAD POISONING affects a variety of victims, including industrially exposed workers and children. A number of methods have been proposed for determining the relationship of the body burden of lead to lead toxicity.1-4 Measurement of erythrocyte o-aminolevulinic acid dehydratase (ALAD) has been used as a monitoring test since activity of this enzyme is depressed by lead. s ,6 Finelli et a1. have reported that ALAD is a zinc-dependent enzyme which requires that metal for both synthesis and activation. 7 ,8 The usual means of treatment of lead toxicity in adults-chelating agents such as calcium disodium edetate (ethylenediaminetetraacetic acid, or EDTA)-results in increased urinary excretion of both lead and zinc. 9 The present report concerns in vitro and in vi.vo investigations of the relationships between ALAD, lead, and zinc in an individual with lead toxicity treated with chelation. The results of the investigati.ons suggest that removal of zinc dur:ing therapy is at least partly responsible for inhibition of ALAD activity and that zinc may playa protective role in cases of lead intoxication. Case Report A 37 ·year-old man who worked for 5 months in a lead battery factory where airborne lead levels were extremely high, and who had previously worked for 25 years as a spray painter using lead-based paints, was referred for evaluation. He complained of having vague pains in the extremities, easy fati.gability, and progressive generalized weakness for a few weeks before admission to the hospital. In addition, he reported headache and loss of appetite with a 13 .6-kg (30-1b) weight loss over the previous 3 months. Hypertension had been diagnosed 3 years earlier. He smoked one package of cigarettes daily and
244
admitted to drinking several pints of whiskey daily for several years. The results of a physical examination were essentially negative except for a blood pressure of 160/100. Two elevated blood lead concentrations, each 260 jlg/100 ml of whole blood (normal limits less than 40 jlg/ 100 ml), had been reported 2 and 4 weeks before admis· si.on. Concentrations of lead and zinc in hair had also been noted to be increased: lead, 3006 ppm (normal limits less than 18 ppm); zinc, 211.7 ppm (normaHimits 140-220 ppm). On admission, hematocrit was 44.2% and hemoglobin was 14.7 g/lOO ml. Nerve conduction velocity and electromyographic studies of the right median and ulnar nerves were interpreted to reveal mild neuropathy and myopathy consistent with excessive alcoholic ingestion, diabetes mellitus, or lead toxicity. The patient was fully informed as to the nature and purpose of the investigation and consented to admission to the Clinical Research Center, University of Cincinnati Medical Center, for study before, during, and 36 days following 5 days of daily parenteral doses of 500 mg EDTA. During these studies specialized investigations were performed which included blood and urine lead and zinc determinations as well as in vitro and in vivo studi.es of erythrocyte ALAD. Immediately following chelation therapy the blood level fell to 100 jlg/lOO ml and the patient became asymptomatic. Thirty-six days after chelation, studies were conducted before and after the oral. administration of 100 mg of zinc sulfate (ZnS04) three times daily for 5 days. The patient had no ill effects from this regimen and was discharged from the hospitaL The last blood lead level recorded was 50 jlg/100 mI.
Archives of Environmental Health
eously with bed rest, and then declined to 100 [J.g/lOO ml following chelation therapy. Zinc sulfate administration produced little change in blood lead levels, as this value was 5S [J.g/IOO ml the day after ZnS04 was di.scontinued. Serum zinc concentrations fell from 146 to 68 [J.g/IOO ml (normal value ± SD, 121 ± 11 [J.g/lOO ml) during chelation, and rose afterward to 138 jJ.g/lOO ml and to a peak of 191 f.lg/lOO ml.15 Zinc sulfate therapy had little effect on serum zinc concentration, which was 103 [J.g/lOO mljust prior to ZnS04 administration, 188-120 f.lg/lOO ml during the therapy, and 106 [J.g/lOO mljust after ZnS04 was discontinued. Twenty-four- hour urinary lead excretion increased with chelation therapy to a high of 2,551 jJ.g/24 ill during the fIrst day of chelation. This value was nearly four times higher than the highest prechelation value. During ZnS04 administration urinary lead excretion remained fairly stable, at low levels. . Twenty-four- hour urinary excretion of zinc increased dramatically during chelation and reached a peale of 6,935 [J.g/24 hr during the last day of therapy. This value was nearly five times greater than the highest prechelation value. During chelation the total urinary excretion of zinc was 27,281 [J.g, nearly four times greater than the 7,719 [J.g oflead excreted. Urinary zinc excretion during ZnS04 administration remained fairly stable. Erythrocyte ALAD activity (nmol porphobilinogen per hour per milliliter of red blood cells) was 204.4 (20% of control) just prior to chelation. Enzyme activity steadily declined during EDTA therapy to a low of 130.7 (12.2%) on day 11. ALAD activity rose to 271.9 (25.5%) on the day after chelation therapy was discontinued. Figure 2
Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 22:15 25 December 2014
Special Studies Blood for determination of serum zinc concentrations was drawn into a plastic syringe and transferred into plastic tubes. The syringe and tubes were first washed wi.th 10% nitric acid and rinsed with deionized water to ensure that they were "metal free." Blood for determination of erythrocyte ALAD activity was collected in a heparini.zed glass tube, covered with a plastic cap, and analyzed within 1 hour after collecti.on. Daily 24-hour urine samples were collected in acid-washed glass containers and kept refrigerated and shielded from light until analysis. Approximately 50 mg of 3- to 4-cm-length nape hair was collected for determination of lead and zinc concentrations. Erythrocyte ALAD acti.vity was assayed by the method of Bonsignore et a1. 10 as modified by Finelli et a1. 8 Zinc and lead concentrations were determined in hair I ! and urine,12 zinc concentrations in serum,13 and lead concentrations in whole blood 14 by atomic absorption spectrophotometry . In vitro addition of zinc chloride (ZnCh) to the patient's erythrocytes was performed as described by Finelli et ill. 7 Reswts In Fi.gure 1 we present concentrations of blood lead and serum zinc and total 24-hour urinary lead and zinc excretion during the 65 days of the study (day 1 = day of hospital admission). Blood lead concentrations declined throughout the study. Values fell from 260 to 140 [J.g/lOO m1 spontan-
24 HOUR URINARY EXCRETION OF Zn AND Pb,SERUM ZI1 AND BLOOD Pb 280
SERUM Zn - - (,ug I IOOml) BLOOD Pb----(,ug/IOOml)
200
120
URINE Zn - - (fl,Ig/24hr.) URINE Pb ----(ft,!g/24hr.)
7000 6000
4000
2000
51
52 53 54 55 56 57 58 59 60 61
62 63 64 65
DAY Fig. L Twenty-fom-houl urinary excretion of zinc Mid lead, serum zinc, md blood lead. Rx '" therapy. Day 1 '" day of hospital. admission.
November/December 1977
245
illustrates these data and also shows the ratio of blood lead to serum zi.nc concentration during this period. The ratio is largest (1.47) on day 11, when ALAn activity is lowest. In vitro studies were performed on day 11. Various concentrations of ZnCh were added to a sample of the patient's erythrocytes, and ALAn activity was determined. The activity increased with increasing concentrations of ZnC1 2 . Values ranged from 130.7 (12.2%) with no ZnCl z added to a high of 1,361.5 (126.7%) when 5 X 10- 4 M ZnClzwas added. In vitro studies were repeated on day 52, prior to ZnS04 administration. Increased ALAD acti.vity with increasing concentrations of ZnCl z , ranging from 3103 (28.6%) with no ZnCh to a maximum of 2,138.9 (197.1 %) with 1 X 10- 4 M ZnC1 2 added, was again noted. Figure 3 presents these data. The table records serial. measurements of the patient's erythrocyte ALAD acti.vity between days 51 and 57, before ZnS04 therapy was begun, and between days 58 and 64, after ZnS04 therapy was i.nstituted. The mean ALAD activity was signifi.cantly higher following ZnS04 therapy (P < .02, by pooled Student's t-test [N = 9]).
1.75
n--
RATIO OF BLOOD Pb/SERUM
1.50
1.25
\
\ 1.00
\ \ \ \
Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 22:15 25 December 2014
.75
\
300
I
250
~
I
,
I
I
I
I
I
200
l
150
Discussion
Fig. 2. ALAD activity and ratio of blood lead to semm zinc. PBG = pOlJlhobilinogen; RBC = red blood cells. Day 1 = day of hospital admJission.
The present investigation substantiates previous in vitro studi.es reporting the interrelati.ons oflead, zinc, and ALAD activity. 5 -9 Finelli et aL showed that ALAn activi.ty of erythrocytes from lead-treated rats was restored to normal levels by the addition of ZnCh. 7 ,8 The in vitro addition of ZnC1 2 to the erythrocytes of the lead-
ALAD ACTIVITY (IN VITRO)
~ll: 2000 '-
~
~
'1,500
~ C( (:i
~
1,00
----+-t--r
,I---I
400
-1
-6
-5
-4
-3
MOLAR CONCENTRATION, LOG[ZnC!2] NORMAL CONTROLS
DAY II - - DAY 52
+
±S D
-
Archives of Environmental Health: An International Journal Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/vzeh20
Lead, Zinc, and Erythrocyte δ-Aminolevulinic Acid Dehydratase: Relationships in Lead Toxicity a
a
a
a
a
Joseph A. Thomasino M. D. , Edward Zuroweste , Stuart M. Brooks M. D. , Harold G. Petering Ph. D. , Sidney I. Lerner M. D. & Vincent N. Finelli Ph. D.
a
a
Department of Environmental Health , University of Cincinnati College of Medicine Published online: 16 Apr 2013.
To cite this article: Joseph A. Thomasino M. D. , Edward Zuroweste , Stuart M. Brooks M. D. , Harold G. Petering Ph. D. , Sidney I. Lerner M. D. & Vincent N. Finelli Ph. D. (1977) Lead, Zinc, and Erythrocyte δ-Aminolevulinic Acid Dehydratase: Relationships in Lead Toxicity, Archives of Environmental Health: An International Journal, 32:6, 244-247, DOI: 10.1080/00039896.1977.10667290 To link to this article: http://dx.doi.org/10.1080/00039896.1977.10667290
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions
Lead, Zinc, inc, and Erythrocyte rythrocyte minolevulinic Acid cid ^®kpiratase ehy atase:: Aminolevulinic .. Relationships Tcxicity el ons . ps in Lead Tomei
Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 22:15 25 December 2014
ة-
JOSEPH A. THOMASINO, M. D. EDWARD ZUROWESTE STUART M. BROOKS, M. D. HAROLD G. PETERING, Ph. D. SIDNEY I. LERNER, M. D. VINCENT N. FINELLI, Ph. D. DepaJrtment of Environmentall Heallth University of Cincinnati College of Medicine ABSTRACT A lead-intoxicated patient with extremely Jrigh blood lead levels and unexpectedly mild symptoms was studied priOl to and following treatment with callcium disodium edetate (ethyleneaiammetetrrultcetic add) and then priOl: to:rnd following mall administration of zinc swiate. During chelation therapy, exytluocyte (o)-aminolewlinic acid dehydratase (ALAn) activity decreased as blood lead levels fell.. UrinaJrY excretion of zinc increased and was more than 3.5 times greater than ilia! of lead. The ratio of blood lead to serum zinc was greatest (1.47) when ALAD activity was lowest. Orall administration of zinc sweate following chelation therapy resulted in a significant increase in mean ALAD actiVlity. In Vlitro additions of zinc chloride to the patient's erylli.rocytes resulted in reactivation of ALAD activity. These studies suggest iliat zinc is an important element in the ALAn system in man. Zinc may playa protective roie in lead toXlicity, and zinc supplementation may be a useful adjull.ct to chelation therapy for lead toXlicity.
LEAD POISONING affects a variety of victims, including industrially exposed workers and children. A number of methods have been proposed for determining the relationship of the body burden of lead to lead toxicity.1-4 Measurement of erythrocyte o-aminolevulinic acid dehydratase (ALAD) has been used as a monitoring test since activity of this enzyme is depressed by lead. s ,6 Finelli et a1. have reported that ALAD is a zinc-dependent enzyme which requires that metal for both synthesis and activation. 7 ,8 The usual means of treatment of lead toxicity in adults-chelating agents such as calcium disodium edetate (ethylenediaminetetraacetic acid, or EDTA)-results in increased urinary excretion of both lead and zinc. 9 The present report concerns in vitro and in vi.vo investigations of the relationships between ALAD, lead, and zinc in an individual with lead toxicity treated with chelation. The results of the investigati.ons suggest that removal of zinc dur:ing therapy is at least partly responsible for inhibition of ALAD activity and that zinc may playa protective role in cases of lead intoxication. Case Report A 37 ·year-old man who worked for 5 months in a lead battery factory where airborne lead levels were extremely high, and who had previously worked for 25 years as a spray painter using lead-based paints, was referred for evaluation. He complained of having vague pains in the extremities, easy fati.gability, and progressive generalized weakness for a few weeks before admission to the hospital. In addition, he reported headache and loss of appetite with a 13 .6-kg (30-1b) weight loss over the previous 3 months. Hypertension had been diagnosed 3 years earlier. He smoked one package of cigarettes daily and
244
admitted to drinking several pints of whiskey daily for several years. The results of a physical examination were essentially negative except for a blood pressure of 160/100. Two elevated blood lead concentrations, each 260 jlg/100 ml of whole blood (normal limits less than 40 jlg/ 100 ml), had been reported 2 and 4 weeks before admis· si.on. Concentrations of lead and zinc in hair had also been noted to be increased: lead, 3006 ppm (normal limits less than 18 ppm); zinc, 211.7 ppm (normaHimits 140-220 ppm). On admission, hematocrit was 44.2% and hemoglobin was 14.7 g/lOO ml. Nerve conduction velocity and electromyographic studies of the right median and ulnar nerves were interpreted to reveal mild neuropathy and myopathy consistent with excessive alcoholic ingestion, diabetes mellitus, or lead toxicity. The patient was fully informed as to the nature and purpose of the investigation and consented to admission to the Clinical Research Center, University of Cincinnati Medical Center, for study before, during, and 36 days following 5 days of daily parenteral doses of 500 mg EDTA. During these studies specialized investigations were performed which included blood and urine lead and zinc determinations as well as in vitro and in vivo studi.es of erythrocyte ALAD. Immediately following chelation therapy the blood level fell to 100 jlg/lOO ml and the patient became asymptomatic. Thirty-six days after chelation, studies were conducted before and after the oral. administration of 100 mg of zinc sulfate (ZnS04) three times daily for 5 days. The patient had no ill effects from this regimen and was discharged from the hospitaL The last blood lead level recorded was 50 jlg/100 mI.
Archives of Environmental Health
eously with bed rest, and then declined to 100 [J.g/lOO ml following chelation therapy. Zinc sulfate administration produced little change in blood lead levels, as this value was 5S [J.g/IOO ml the day after ZnS04 was di.scontinued. Serum zinc concentrations fell from 146 to 68 [J.g/IOO ml (normal value ± SD, 121 ± 11 [J.g/lOO ml) during chelation, and rose afterward to 138 jJ.g/lOO ml and to a peak of 191 f.lg/lOO ml.15 Zinc sulfate therapy had little effect on serum zinc concentration, which was 103 [J.g/lOO mljust prior to ZnS04 administration, 188-120 f.lg/lOO ml during the therapy, and 106 [J.g/lOO mljust after ZnS04 was discontinued. Twenty-four- hour urinary lead excretion increased with chelation therapy to a high of 2,551 jJ.g/24 ill during the fIrst day of chelation. This value was nearly four times higher than the highest prechelation value. During ZnS04 administration urinary lead excretion remained fairly stable, at low levels. . Twenty-four- hour urinary excretion of zinc increased dramatically during chelation and reached a peale of 6,935 [J.g/24 hr during the last day of therapy. This value was nearly five times greater than the highest prechelation value. During chelation the total urinary excretion of zinc was 27,281 [J.g, nearly four times greater than the 7,719 [J.g oflead excreted. Urinary zinc excretion during ZnS04 administration remained fairly stable. Erythrocyte ALAD activity (nmol porphobilinogen per hour per milliliter of red blood cells) was 204.4 (20% of control) just prior to chelation. Enzyme activity steadily declined during EDTA therapy to a low of 130.7 (12.2%) on day 11. ALAD activity rose to 271.9 (25.5%) on the day after chelation therapy was discontinued. Figure 2
Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 22:15 25 December 2014
Special Studies Blood for determination of serum zinc concentrations was drawn into a plastic syringe and transferred into plastic tubes. The syringe and tubes were first washed wi.th 10% nitric acid and rinsed with deionized water to ensure that they were "metal free." Blood for determination of erythrocyte ALAD activity was collected in a heparini.zed glass tube, covered with a plastic cap, and analyzed within 1 hour after collecti.on. Daily 24-hour urine samples were collected in acid-washed glass containers and kept refrigerated and shielded from light until analysis. Approximately 50 mg of 3- to 4-cm-length nape hair was collected for determination of lead and zinc concentrations. Erythrocyte ALAD acti.vity was assayed by the method of Bonsignore et a1. 10 as modified by Finelli et a1. 8 Zinc and lead concentrations were determined in hair I ! and urine,12 zinc concentrations in serum,13 and lead concentrations in whole blood 14 by atomic absorption spectrophotometry . In vitro addition of zinc chloride (ZnCh) to the patient's erythrocytes was performed as described by Finelli et ill. 7 Reswts In Fi.gure 1 we present concentrations of blood lead and serum zinc and total 24-hour urinary lead and zinc excretion during the 65 days of the study (day 1 = day of hospital admission). Blood lead concentrations declined throughout the study. Values fell from 260 to 140 [J.g/lOO m1 spontan-
24 HOUR URINARY EXCRETION OF Zn AND Pb,SERUM ZI1 AND BLOOD Pb 280
SERUM Zn - - (,ug I IOOml) BLOOD Pb----(,ug/IOOml)
200
120
URINE Zn - - (fl,Ig/24hr.) URINE Pb ----(ft,!g/24hr.)
7000 6000
4000
2000
51
52 53 54 55 56 57 58 59 60 61
62 63 64 65
DAY Fig. L Twenty-fom-houl urinary excretion of zinc Mid lead, serum zinc, md blood lead. Rx '" therapy. Day 1 '" day of hospital. admission.
November/December 1977
245
illustrates these data and also shows the ratio of blood lead to serum zi.nc concentration during this period. The ratio is largest (1.47) on day 11, when ALAn activity is lowest. In vitro studies were performed on day 11. Various concentrations of ZnCh were added to a sample of the patient's erythrocytes, and ALAn activity was determined. The activity increased with increasing concentrations of ZnC1 2 . Values ranged from 130.7 (12.2%) with no ZnCl z added to a high of 1,361.5 (126.7%) when 5 X 10- 4 M ZnClzwas added. In vitro studies were repeated on day 52, prior to ZnS04 administration. Increased ALAD acti.vity with increasing concentrations of ZnCl z , ranging from 3103 (28.6%) with no ZnCh to a maximum of 2,138.9 (197.1 %) with 1 X 10- 4 M ZnC1 2 added, was again noted. Figure 3 presents these data. The table records serial. measurements of the patient's erythrocyte ALAD acti.vity between days 51 and 57, before ZnS04 therapy was begun, and between days 58 and 64, after ZnS04 therapy was i.nstituted. The mean ALAD activity was signifi.cantly higher following ZnS04 therapy (P < .02, by pooled Student's t-test [N = 9]).
1.75
n--
RATIO OF BLOOD Pb/SERUM
1.50
1.25
\
\ 1.00
\ \ \ \
Downloaded by [UZH Hauptbibliothek / Zentralbibliothek Zürich] at 22:15 25 December 2014
.75
\
300
I
250
~
I
,
I
I
I
I
I
200
l
150
Discussion
Fig. 2. ALAD activity and ratio of blood lead to semm zinc. PBG = pOlJlhobilinogen; RBC = red blood cells. Day 1 = day of hospital admJission.
The present investigation substantiates previous in vitro studi.es reporting the interrelati.ons oflead, zinc, and ALAD activity. 5 -9 Finelli et aL showed that ALAn activi.ty of erythrocytes from lead-treated rats was restored to normal levels by the addition of ZnCh. 7 ,8 The in vitro addition of ZnC1 2 to the erythrocytes of the lead-
ALAD ACTIVITY (IN VITRO)
~ll: 2000 '-
~
~
'1,500
~ C( (:i
~
1,00
----+-t--r
,I---I
400
-1
-6
-5
-4
-3
MOLAR CONCENTRATION, LOG[ZnC!2] NORMAL CONTROLS
DAY II - - DAY 52
+
±S D
-
