- Email: [email protected]
Dietary fat alteration of plasma cholinesterase response to malathion
Toxicology, 5 (1975) 113--115 © Elsevier/North-Holland, Amsterdam -- Printed in the Netherlands
DIETARY FAT ALTERATION OF PLASMA CHOLINESTERASE RESPONSE TO MALATHION
PRISCILLA POWELL DAVIDSON School of Pharmacy, Auburn University, Auburn, Ala. 36830 (U.S.A.)
(Received November 24th, 1974) (Revision received May 20th, 1975) (Accepted June 2nd, 1975)
SUMMARY This study revealed the influence of organophosphate pesticides on cholinesterase levels of male Sprague-Dawley rats. Subjects were fed fat-free, normal-fat, and high-fat test diets. Sub-acute doses of malathion were given subcutaneously and cholinesterase levels were determined. Malathion was chosen because it is the least toxic of the organophosphate cholinesteraseinhibiting pesticides. Statistical analysis of the data showed that malathion does inhibit blood cholinesterase to the greatest degree in normal-fat diet animals, with the least effect on high-fat groups and fat-free subjects fall in between the two groups.
INTRODUCTION The organophosphates are powerful cholinesterase inhibitor agents [1,2]. This reported observation, considered with the evidence that organic phosphate inhibitors or their metabolites are stored in adipose tissue until they can be eliminated from the body [3] suggested value in the investigation of varied levels of dietary lipid on cholinesterase response to organic phosphate cholinesterase inhibitors. Malathion, a c o m m o n l y used organic phosphate pesticide, was used in this investigation to determine the possible effect of alteration of dietary intake of fat on cholinesterase activity of plasma and on the response of plasma cholinesterase activity to systematically administered malathion.
113
EXPERIMENTAL 24 m a l e S p r a g u e - D a w l e y rats ( 1 8 0 - 2 0 0 g; C h e r o k e e L a b o r a t o r y S u p p l y Co., A t l a n t a , Georgia) were divided i n t o f o u r g r o u p s of 6 rats each. One g r o u p was fed a fat-free diet { N u t r i t i o n a l B i o c h e m i c a l s C o r p o r a t i o n F a t - F r e e T e s t Diet); a s e c o n d g r o u p was fed a n o r m a l diet (Purina L a b o r a t o r y C h o w ) ; a t h i r d g r o u p received a high-fat diet ( N u t r i t i o n a l B i o c h e m i c a l s C o r p o r a t i o n H i g h - F a t T e s t Diet). F a t c o n t e n t o f the n o r m a l a n d high fat diets were 4.5% a n d 45%, r e s p e c t i v e l y . T h e f o u r t h g r o u p served as t h e c o n t r o l g r o u p and was also fed a n o r m a l - f a t diet. T h e a n i m a l s were m a i n t a i n e d o n these diets f o r a p e r i o d of 5 weeks. A t this t i m e p l a s m a c h o l i n e s t e r a s e levels were d e t e r m i n e d . On t h e following d a y all g r o u p s e x c e p t t h e c o n t r o l g r o u p were injected w i t h a dose of 2 0 0 m g / k g o f m a l a t h i o n ( M a l a t h i o n S e c o n d a r y S t a n d a r d , m a n u f a c tured by: American Cyanamid C o m p a n y ) subcutaneously. Blood samples were t a k e n f r o m all f o u r o f t h e g r o u p s 6 h later and p l a s m a c h o l i n e s t e r a s e a c t i v i t y d e t e r m i n e d . 3 d a y s later the t e s t groups, e x c l u d i n g t h e c o n t r o l g r o u p , were again injected w i t h the s a m e a m o u n t o f m a l a t h i o n . A t the end o f 6 h the animals were sacrificed a n d p l a s m a c h o l i n e s t e r a s e assay was again carried out. T h e c h o l i n e s t e r a s e d e t e r m i n a t i o n s were d o w n b y the p H - S T A T m e t h o d as carried o u t b y t h e C o l o r a d o a n d I o w a C o m m u n i t y Pesticide S t u d y Project [ 4 ] . B l o o d f o r all e x c e p t t h e final assays was t a k e n f r o m t h e tail and t h a t f o r t h e final assay f r o m t h e h e a r t o f the rat. RESULTS AND DISCUSSION Data p r e s e n t e d in T a b l e I reveal t h e decrease in p l a s m a c h o l i n e s t e r a s e activity i n d u c e d b y m a l a t h i o n u n d e r v a r y i n g d i e t a r y regimens. A l t e r a t i o n s of TABLE I RAT PLASMA CHOLINESTERASE ALTERATION BY MALATHION AS INFLUENCED BY DIETARY FAT Group
Fat-free Normal-fat High-fat Control (no malathion administered)
Mean cholinesterase activity in pmoles/min/ml Day 35, Premalathion
Day 36 -- 6 h after first dose of malathion
% Decrease
Day 39 -- 6 h after second dose of malathion
% Decrease
0.097 a 0.048 0.055
0.071 0.022 0.040
26.8 54.2 b 27.3
0.070 0.033 0.053
27.9 31.2 3.67 c
0.057
0.058
1.8
0.053
7
a Significantly different from control value. Significantly different from corresponding value for all other groups. c Significantly different from corresponding values for fat-free and normal-fat groups.
b
114
the cholinesterase activity reduction by dietary changes in fat intake are apparent in the data with the least reduction in the high fat group and the greatest r educt i on in the normal diet group. It m a y be significant that an impressive increase in plasma cholinesterase activity was induced by the fat free diet prior to malathion dosing, an u n e x p e c t e d effect in view o f reports of elevated cholinesterase levels in the blood of obese subjects. The effects o f dietary fat alteration on the plasma cholinesterase are well within the range of statistical significance following the first dose of malathion. Both the high fat diet and the low fat diet reduced the~response of plasma cholinesterase to malathion as contrasted with t h e normal fat diet. This pattern was n o t seen after the second dose with the fat-free and normal groups revealing a similar responsiveness and the high-fat group a significantly lowered responsiveness to malathion. REFERENCES 1 A. Fatteh, Handbook of Forensic Pathology, Lippincott, Philadelphia, 1973, p. 311. 2 T.A. Loomis, Essentials of Toxicology, Lea and Febiger, Philadelphia, 1974, p. 35. 3 C.H. Thienes and T.J. Haley, Clinical Toxicology, Lea and Febiger, Philadelphia, 1972, p. 112. 4 Colorado and Iowa Community Pesticide Study Project Committee, 1, 1968.
115
DIETARY FAT ALTERATION OF PLASMA CHOLINESTERASE RESPONSE TO MALATHION
PRISCILLA POWELL DAVIDSON School of Pharmacy, Auburn University, Auburn, Ala. 36830 (U.S.A.)
(Received November 24th, 1974) (Revision received May 20th, 1975) (Accepted June 2nd, 1975)
SUMMARY This study revealed the influence of organophosphate pesticides on cholinesterase levels of male Sprague-Dawley rats. Subjects were fed fat-free, normal-fat, and high-fat test diets. Sub-acute doses of malathion were given subcutaneously and cholinesterase levels were determined. Malathion was chosen because it is the least toxic of the organophosphate cholinesteraseinhibiting pesticides. Statistical analysis of the data showed that malathion does inhibit blood cholinesterase to the greatest degree in normal-fat diet animals, with the least effect on high-fat groups and fat-free subjects fall in between the two groups.
INTRODUCTION The organophosphates are powerful cholinesterase inhibitor agents [1,2]. This reported observation, considered with the evidence that organic phosphate inhibitors or their metabolites are stored in adipose tissue until they can be eliminated from the body [3] suggested value in the investigation of varied levels of dietary lipid on cholinesterase response to organic phosphate cholinesterase inhibitors. Malathion, a c o m m o n l y used organic phosphate pesticide, was used in this investigation to determine the possible effect of alteration of dietary intake of fat on cholinesterase activity of plasma and on the response of plasma cholinesterase activity to systematically administered malathion.
113
EXPERIMENTAL 24 m a l e S p r a g u e - D a w l e y rats ( 1 8 0 - 2 0 0 g; C h e r o k e e L a b o r a t o r y S u p p l y Co., A t l a n t a , Georgia) were divided i n t o f o u r g r o u p s of 6 rats each. One g r o u p was fed a fat-free diet { N u t r i t i o n a l B i o c h e m i c a l s C o r p o r a t i o n F a t - F r e e T e s t Diet); a s e c o n d g r o u p was fed a n o r m a l diet (Purina L a b o r a t o r y C h o w ) ; a t h i r d g r o u p received a high-fat diet ( N u t r i t i o n a l B i o c h e m i c a l s C o r p o r a t i o n H i g h - F a t T e s t Diet). F a t c o n t e n t o f the n o r m a l a n d high fat diets were 4.5% a n d 45%, r e s p e c t i v e l y . T h e f o u r t h g r o u p served as t h e c o n t r o l g r o u p and was also fed a n o r m a l - f a t diet. T h e a n i m a l s were m a i n t a i n e d o n these diets f o r a p e r i o d of 5 weeks. A t this t i m e p l a s m a c h o l i n e s t e r a s e levels were d e t e r m i n e d . On t h e following d a y all g r o u p s e x c e p t t h e c o n t r o l g r o u p were injected w i t h a dose of 2 0 0 m g / k g o f m a l a t h i o n ( M a l a t h i o n S e c o n d a r y S t a n d a r d , m a n u f a c tured by: American Cyanamid C o m p a n y ) subcutaneously. Blood samples were t a k e n f r o m all f o u r o f t h e g r o u p s 6 h later and p l a s m a c h o l i n e s t e r a s e a c t i v i t y d e t e r m i n e d . 3 d a y s later the t e s t groups, e x c l u d i n g t h e c o n t r o l g r o u p , were again injected w i t h the s a m e a m o u n t o f m a l a t h i o n . A t the end o f 6 h the animals were sacrificed a n d p l a s m a c h o l i n e s t e r a s e assay was again carried out. T h e c h o l i n e s t e r a s e d e t e r m i n a t i o n s were d o w n b y the p H - S T A T m e t h o d as carried o u t b y t h e C o l o r a d o a n d I o w a C o m m u n i t y Pesticide S t u d y Project [ 4 ] . B l o o d f o r all e x c e p t t h e final assays was t a k e n f r o m t h e tail and t h a t f o r t h e final assay f r o m t h e h e a r t o f the rat. RESULTS AND DISCUSSION Data p r e s e n t e d in T a b l e I reveal t h e decrease in p l a s m a c h o l i n e s t e r a s e activity i n d u c e d b y m a l a t h i o n u n d e r v a r y i n g d i e t a r y regimens. A l t e r a t i o n s of TABLE I RAT PLASMA CHOLINESTERASE ALTERATION BY MALATHION AS INFLUENCED BY DIETARY FAT Group
Fat-free Normal-fat High-fat Control (no malathion administered)
Mean cholinesterase activity in pmoles/min/ml Day 35, Premalathion
Day 36 -- 6 h after first dose of malathion
% Decrease
Day 39 -- 6 h after second dose of malathion
% Decrease
0.097 a 0.048 0.055
0.071 0.022 0.040
26.8 54.2 b 27.3
0.070 0.033 0.053
27.9 31.2 3.67 c
0.057
0.058
1.8
0.053
7
a Significantly different from control value. Significantly different from corresponding value for all other groups. c Significantly different from corresponding values for fat-free and normal-fat groups.
b
114
the cholinesterase activity reduction by dietary changes in fat intake are apparent in the data with the least reduction in the high fat group and the greatest r educt i on in the normal diet group. It m a y be significant that an impressive increase in plasma cholinesterase activity was induced by the fat free diet prior to malathion dosing, an u n e x p e c t e d effect in view o f reports of elevated cholinesterase levels in the blood of obese subjects. The effects o f dietary fat alteration on the plasma cholinesterase are well within the range of statistical significance following the first dose of malathion. Both the high fat diet and the low fat diet reduced the~response of plasma cholinesterase to malathion as contrasted with t h e normal fat diet. This pattern was n o t seen after the second dose with the fat-free and normal groups revealing a similar responsiveness and the high-fat group a significantly lowered responsiveness to malathion. REFERENCES 1 A. Fatteh, Handbook of Forensic Pathology, Lippincott, Philadelphia, 1973, p. 311. 2 T.A. Loomis, Essentials of Toxicology, Lea and Febiger, Philadelphia, 1974, p. 35. 3 C.H. Thienes and T.J. Haley, Clinical Toxicology, Lea and Febiger, Philadelphia, 1972, p. 112. 4 Colorado and Iowa Community Pesticide Study Project Committee, 1, 1968.
115