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Depression of fatty acid synthesis in chick liver (Gallus domesticus) by aflatoxin
Comp. Biochem. Physiol., 1972, Vol. 411t,pp. 843 to 847. Pergamon Press. Printed in Great Britain
DEPRESSION OF FATTY ACID SYNTHESIS IN CHICK LIVER (GALLUS DOMESTICUS) BY AFLATOXIN W. E. D O N A L D S O N , H S I - T A N G T U N G and P. B. H A M I L T O N Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27607 (Received 7 September 1971)
Abstract--1. Dietary aflatoxin reduced the incorporation of acetate-~4C into long-chain fatty acids of chick liver (Gallus domesticus) in a dose-related fashion. 2. Feeding 10/~g of aflatoxin per g of diet for 3 weeks depressed the activities of the microsomal system of fatty acid elongation and fatty acid synthetase in liver. 3. Crystalline aflatoxin did not inhibit fatty acid synthetase in vitro at levels up to 20 ktg/ml of incubation medium. 4. It is suggested that aflatoxin exerts its effects on lipogenesis by depressing the formation of the enzymes involved in fatty acid synthesis. INTRODUCTION AFLATOXlN B 1 is a potent hepatotoxin produced by the fungus, Aspergillus f l a v u s (Asao et al., 1963). Although carcinogenic for some species such as the rat (Wogan & Newberne, 1967) aflatoxin is acutely toxic in chickens (Smith & Hamilton, 1970). In the rat, the primary effect of aflatoxin appears to be an interaction with D N A to depress the formation of messenger RNA and thus protein synthesis according to Clifford & Rees (1967) and Pong & Wogan (1969). Smith & Hamilton (1970) reported that aflatoxicosis in chickens was characterized by depressed growth rate, increased lipid content of the liver and decreased lipid content of the extra-hepatic tissues. Shank & Wogan (1966) observed similar effects on lipid metabolism in the duckling along with decreased incorporation of radioactive glucose into liver lipids and suggested that these effects were the result of interference with lipid transport. A similar inhibition of the incorporation of labeled acetate into lipids has been reported for rat liver by Kato et al. (1969) and for human skin by Black et al. (1970), and in both instances, the authors suggested that it was a specific inhibition and not the result of general hepatic injury or toxicity. However, there have been no studies on the mechanism by which aflatoxin exerts its effect on fatty acid synthesis. Since 90-95 per cent of the total fatty acid synthesis in chicks occurs in their livers (O'Hea & Leveille, 1969), the chick appeared to be a good experimental animal to study the effects of aflatoxin. This paper reports the results of experiments in which fatty acid synthesis was measured in intact chicks or livers from chicks fed graded doses of aflatoxin and in enzyme preparations containing graded amounts of added aflatoxin. 843
844
W.E. DONALDSON,HsI-TANGTUNGANDP. B. HAMILTON
MATERIALS AND METHODS In experiment I, day-oldchicks were fed a commercial diet to which was added 0, 1-25, 2.5, 5"0 or 10"0/zg of aflatoxin per g of diet. The methods for aflatoxin production have been described by Smith & Hamilton (1970). At 3 weeks of age, five chicks from each dietary treatment were each injected intraperitoneally with 1/xc of sodium 1-14C acetate. At 30 min post-injection, the chicks were killed and their livers were removed and frozen until analyzed. Acetate-t4C incorporation into long-chain fatty acids was determined for each liver as described by Donaldson (1967). In experiment 2, day-old chicks were fed a commercial diet containing either 0 or 10/zg of aflatoxin per g of diet. At 3 weeks of age, four chicks from each dietary treatment were killed and their livers were removed and placed in 0.25 M sucrose. Each liver was homogenized, and the homogenate was centrifuged for 10 min at 800 g. All steps were carried out at 0-5°C. The supernatant fractions were analyzed for protein by the biuret method of Cleland & Slater (1953). Each supernatant was assayed immediately for fatty acid synthesizing capacity by the microsomal system of fatty acid elongation and the fatty acid synthetase system. Donaldson et al. (1970) have shown that these two synthetic systems can be measured independently and have described the assay conditions. In a final experiment 0, 0"2, 2 and 20/~g of crystalline aflatoxin (Calbiochem, San Diego, Calif., U.S.A.) were added per ml of the medium used to assay fatty acid synthetase in the 100,000 g supernatant fraction of liver from chicks not fed aflatoxin. RESULTS AND DISCUSSION The effects of graded doses of aflatoxin on the in vivo incorporation of acetateI~C into long-chain fatty acids of chick liver are shown in Table I. There was a TABLE 1 - - E F F E C T OF GRADED DOSES OF DIETARY AFLATOXIN ON ACETATE-l-14C INCORPORATION INTO LIVER FATTY ACIDS IN INTACT CHICKS (EXPERIMENT 1)
Dietary aflatoxin (/~g/g) 0 1-25 2.5 5.0 10.0
Acetate-14C incorporation into per cent of dose* 6.1±2.0 4.2±0.9 2.4±0.5 2.0±0.3 3.2±0.9
Statistical significance (P) -N.S. <0.05 <0.02 <0.05
* Each value is the mean +_S.E. for five chicks. The chicks were injected intraperitoneaUy with 1/xc of sodium 1-14C acetate. Incorporation was measured 30 min post-injection. Probabilities are based upon t-test comparisons of each mean with the control mean. dose related decrease, and at the higher doses of aflatoxin the i n c o r p o r a t i o n of acetate into liver fatty acids was a b o u t o n e - t h i r d of the control value. T a b l e 2 shows the effect of dietary aflatoxin on the specific activities of the m i c r o s o m a l s y s t e m of fatty acid elongation and of fatty acid synthetase. T h e s e in vitro assays revealed t h a t b o t h systems of fatty acid synthesis were depressed to a b o u t onef o u r t h o f control values. B o t h depressions were statistically significant ( P < 0.05).
DEPRESSION OF FATTY ACID SYNTHESIS I N CHICK LIVER BY AFLATOXIN
845
T A B L E 2 - - E F F E C T OF DIETARY AFLATOXIN ON THE ACTIVITIES OF THE MICROSOMAL SYSTEM OF FATTY ACID ELONGATION AND OF FATTY ACID SYNTHETASE I N H O M O GENATES OF CHICK LIVER (EXPERIMENT 2)
Dietary aflatoxin (/zg/g) 0 10
Microsomal system of elongation*
Fatty acid synthetase*
1088 + 309 242 + 66
2264 + 717 540 + 155
* Each value is the mean + S.E. for four chicks expressed as picomoles of malonyl-CoA incorporated into long-chain fatty acids/min per mg protein. The incubation medium for both assays contained 90 mM KC1, 50 mM potassium phosphate buffer (pH 7"4), 1 mM EDTA, 5 mM MgCI2, 5 mM KCN, 5 mM NADPH and 0"3 mM 1- or 3-14C malonyl-CoA. The medium for the microsomal system also contained 10 mM ATP. The medium for fatty acid synthetase was the same as the medium for the microsomal system except that ATP w a s omitted and 39/~M unlabeled acetyl-CoA was added. The assays were for 20 min at 25°C. In another experiment, pure aflatoxin B1, even at the high concentration of 20/~g/ml of incubation medium, was without effect on the fatty acid synthetase activity of the 100,000 g supernatant fraction of liver from chicks not fed aflatoxin. The decreased incorporation in vivo of labeled acetate into the long-chain fatty acids of liver of chicks fed aflatoxin indicate that fatty acid synthesis is inhibited during aflatoxicosis. The decrease of fatty acid synthesis concomitant with an accumulation of lipid in liver (Smith & Hamilton, 1970) suggests strongly that the mobilization of hepatic lipids and/or the transport of these lipids to peripheral tissue are inhibited during aflatoxicosis. Shank & Wogan (1966) reached a similar conclusion after observing a decreased incorporation of labeled glucose into liver lipids concomitant with a rise in total lipid of the liver of ducklings. The reduced specific activity of fatty acid synthesizing enzymes in liver homogenates from chicks fed aflatoxin and the failure of aflatoxin to inhibit these enzymes when added to homogenates from chicks not fed aflatoxin suggest that aflatoxin exerts its effect on lipogenesis by depressing somehow the formation of the enzymes involved in fatty acid synthesis. A ready mechanism for such an inhibition exists in the studies of Clifford & Rees (1967), Pong & Wogan (1969) and Lafarge & Frayssinet (1970) who hypothesized that aflatoxin binds to D N A and thus interferes with RNA polymerase and subsequently with protein synthesis. However, such a simple and well-founded mechanism does not appear to explain the apparent specificity of the inhibition of lipid synthesis by aflatoxin, since the inhibitory doses are smaller than those required to inhibit growth (Smith & Hamilton, 1970). Lipid synthesis in human skin slices is reduced after only a few hours' incubation with aflatoxin (Black et al., 1970) and kinetic experiments with perfused rat liver revealed a cytotoxic effect before any effect on metabolism of blood proteins could be observed (John & Miller, 1969). In the chicken, lipid transport is altered by
846
W. E. DONALDSON,HsI-TANG TUNG and P. B. HAMILTON
smaller doses than are required to depress growth rate ( T u n g et al., 1971). Thus, the hypothesis of a general inhibition of R N A polymerase as a result of binding of aflatoxin to D N A would appear to need modification to allow for the specific inhibition of lipid synthesis and transport. Such a modification may reside in the findings and ideas of Lafarge & Frayssinet (1970) that the formation of long messenger R N A is more severely affected by aflatoxin than is the formation of short messenger RNA. I n any case, it would appear that further investigation into effects of aflatoxin on lipid metabolism and nucleic acid metabolism will be needed before a detailed understanding of aflatoxicosis is obtained.
Acknowledgements--This is Paper No. 3525 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina. This research was supported in part by the U.S. Public Health Service, Grant No. HD-02887, National Institutes of Health. The technical assistance of Mrs. F. D. Suggs and Mr. C. Strickland is gratefully acknowledged. REFERENCES ASAO T., BUCHI G., ABHEL-KADERM. M., CHANG S. B., WICK E. L. & WOGAN G. N. (1970) Aflatoxins B and G. j% Am. Chem. Soc. 85, 1706-1707. BLACKH. S., SMITHJ. D., AUSTINB. J. & RAUSCHKOLBE. W. (1969) Effect of aflatoxin B1 on the in vitro incorporation of 14C-acetate into human skin lipids. Experientia 26, 1292-1293. CLELANDK. W. ~ SLATERE. C. (1953) Respiratory granules of heart muscle. Biochem. J. 53, 547-556. CLIFFORD J. I. ~ REES K. R. (1967) The action of aflatoxin BI on the rat liver. Biochem.J. 102, 65-75. DONALDSONW. E. (1967) Influence of biotin deficiency and dietary sterculic acid on fatty acid dehydrogenation. Biochem. biophys. Res. Commun. 26, 539-543. DONALDSONW. E., WIT-PEETERSE. M. & SCHOLTEH. R. (1970) Fatty acid synthesis in rat liver: relative contributions of the mitochondrial microsomal and non-particulate systems. Biochim. biophys. Acta 202, 35-42. JOHN D. W. & MILL~.R L. L. (1969) Effect of aflatoxin B1 on net synthesis of albumin, fibrinogen and a-1 acid glycoprotein by the isolated perfused rat liver. Biochem. Pharmac. 18, 1135-1146. KATO R., ONODAK. & OMORI Y. (1969) Effect of aflatoxin B1 on the incorporation of 14Cacetate into cholesterol by rat liver. Experientia 25, 1026. LAFARGE C. & FRAYSSINETC. (1970) The reversibility of inhibition of RNA and DNA synthesis induced by aflatoxin in rat liver. A tentative explanation for carcinogenic mechanism. Int..~. Cancer 6, 74-83. O'HEA E. K. & LEVEILLEG. A. (1969) Lipid biosynthesis and transport in the domestic chick (Gallus domesticus). Comp. Biochem. Physiol. 30, 149-159. PONG R. S. & WOGANG. N. (1969) Time course of alterations of rat liver polysome profiles induced by aflatoxin BI. Biochem. Pharmac. 18, 2357-2361. SHANKR. C. & WOGANG. N. (1966) Acute effects of aflatoxin B, on liver composition and metabolism in the rat and duckling. Toxic. Appl. Pharmacol. 9, 468-476. SMITH J. W. & HAMILTONP. n. (1970) Aflatoxicosis in the broiler chicken. Poult. Sci. 49, 207-215. TUNG H. T., DONALDSONW. E. &HAMILTONP. B. (1971) Altered lipid transport during aflatoxicosis. Toxicol. Appl. Pharmacol. (In press.)
DEPRESSION OF FATTY ACID SYNTHESIS I N CHICK LIVER BY AFLATOXIN
847
WOGAN G. N. & NEWBERNE P. M. (1967) Dose-response characteristics of aflatoxin Bt carcinogenesis in the rat. Cancer Res. 27, 2370-2376. Key Word Index--Gallus domesticus; microsomes; fatty acid synthesis; synthetase of fatty acids; aflatoxin; lipogenesis.
DEPRESSION OF FATTY ACID SYNTHESIS IN CHICK LIVER (GALLUS DOMESTICUS) BY AFLATOXIN W. E. D O N A L D S O N , H S I - T A N G T U N G and P. B. H A M I L T O N Department of Poultry Science, North Carolina State University, Raleigh, North Carolina 27607 (Received 7 September 1971)
Abstract--1. Dietary aflatoxin reduced the incorporation of acetate-~4C into long-chain fatty acids of chick liver (Gallus domesticus) in a dose-related fashion. 2. Feeding 10/~g of aflatoxin per g of diet for 3 weeks depressed the activities of the microsomal system of fatty acid elongation and fatty acid synthetase in liver. 3. Crystalline aflatoxin did not inhibit fatty acid synthetase in vitro at levels up to 20 ktg/ml of incubation medium. 4. It is suggested that aflatoxin exerts its effects on lipogenesis by depressing the formation of the enzymes involved in fatty acid synthesis. INTRODUCTION AFLATOXlN B 1 is a potent hepatotoxin produced by the fungus, Aspergillus f l a v u s (Asao et al., 1963). Although carcinogenic for some species such as the rat (Wogan & Newberne, 1967) aflatoxin is acutely toxic in chickens (Smith & Hamilton, 1970). In the rat, the primary effect of aflatoxin appears to be an interaction with D N A to depress the formation of messenger RNA and thus protein synthesis according to Clifford & Rees (1967) and Pong & Wogan (1969). Smith & Hamilton (1970) reported that aflatoxicosis in chickens was characterized by depressed growth rate, increased lipid content of the liver and decreased lipid content of the extra-hepatic tissues. Shank & Wogan (1966) observed similar effects on lipid metabolism in the duckling along with decreased incorporation of radioactive glucose into liver lipids and suggested that these effects were the result of interference with lipid transport. A similar inhibition of the incorporation of labeled acetate into lipids has been reported for rat liver by Kato et al. (1969) and for human skin by Black et al. (1970), and in both instances, the authors suggested that it was a specific inhibition and not the result of general hepatic injury or toxicity. However, there have been no studies on the mechanism by which aflatoxin exerts its effect on fatty acid synthesis. Since 90-95 per cent of the total fatty acid synthesis in chicks occurs in their livers (O'Hea & Leveille, 1969), the chick appeared to be a good experimental animal to study the effects of aflatoxin. This paper reports the results of experiments in which fatty acid synthesis was measured in intact chicks or livers from chicks fed graded doses of aflatoxin and in enzyme preparations containing graded amounts of added aflatoxin. 843
844
W.E. DONALDSON,HsI-TANGTUNGANDP. B. HAMILTON
MATERIALS AND METHODS In experiment I, day-oldchicks were fed a commercial diet to which was added 0, 1-25, 2.5, 5"0 or 10"0/zg of aflatoxin per g of diet. The methods for aflatoxin production have been described by Smith & Hamilton (1970). At 3 weeks of age, five chicks from each dietary treatment were each injected intraperitoneally with 1/xc of sodium 1-14C acetate. At 30 min post-injection, the chicks were killed and their livers were removed and frozen until analyzed. Acetate-t4C incorporation into long-chain fatty acids was determined for each liver as described by Donaldson (1967). In experiment 2, day-old chicks were fed a commercial diet containing either 0 or 10/zg of aflatoxin per g of diet. At 3 weeks of age, four chicks from each dietary treatment were killed and their livers were removed and placed in 0.25 M sucrose. Each liver was homogenized, and the homogenate was centrifuged for 10 min at 800 g. All steps were carried out at 0-5°C. The supernatant fractions were analyzed for protein by the biuret method of Cleland & Slater (1953). Each supernatant was assayed immediately for fatty acid synthesizing capacity by the microsomal system of fatty acid elongation and the fatty acid synthetase system. Donaldson et al. (1970) have shown that these two synthetic systems can be measured independently and have described the assay conditions. In a final experiment 0, 0"2, 2 and 20/~g of crystalline aflatoxin (Calbiochem, San Diego, Calif., U.S.A.) were added per ml of the medium used to assay fatty acid synthetase in the 100,000 g supernatant fraction of liver from chicks not fed aflatoxin. RESULTS AND DISCUSSION The effects of graded doses of aflatoxin on the in vivo incorporation of acetateI~C into long-chain fatty acids of chick liver are shown in Table I. There was a TABLE 1 - - E F F E C T OF GRADED DOSES OF DIETARY AFLATOXIN ON ACETATE-l-14C INCORPORATION INTO LIVER FATTY ACIDS IN INTACT CHICKS (EXPERIMENT 1)
Dietary aflatoxin (/~g/g) 0 1-25 2.5 5.0 10.0
Acetate-14C incorporation into per cent of dose* 6.1±2.0 4.2±0.9 2.4±0.5 2.0±0.3 3.2±0.9
Statistical significance (P) -N.S. <0.05 <0.02 <0.05
* Each value is the mean +_S.E. for five chicks. The chicks were injected intraperitoneaUy with 1/xc of sodium 1-14C acetate. Incorporation was measured 30 min post-injection. Probabilities are based upon t-test comparisons of each mean with the control mean. dose related decrease, and at the higher doses of aflatoxin the i n c o r p o r a t i o n of acetate into liver fatty acids was a b o u t o n e - t h i r d of the control value. T a b l e 2 shows the effect of dietary aflatoxin on the specific activities of the m i c r o s o m a l s y s t e m of fatty acid elongation and of fatty acid synthetase. T h e s e in vitro assays revealed t h a t b o t h systems of fatty acid synthesis were depressed to a b o u t onef o u r t h o f control values. B o t h depressions were statistically significant ( P < 0.05).
DEPRESSION OF FATTY ACID SYNTHESIS I N CHICK LIVER BY AFLATOXIN
845
T A B L E 2 - - E F F E C T OF DIETARY AFLATOXIN ON THE ACTIVITIES OF THE MICROSOMAL SYSTEM OF FATTY ACID ELONGATION AND OF FATTY ACID SYNTHETASE I N H O M O GENATES OF CHICK LIVER (EXPERIMENT 2)
Dietary aflatoxin (/zg/g) 0 10
Microsomal system of elongation*
Fatty acid synthetase*
1088 + 309 242 + 66
2264 + 717 540 + 155
* Each value is the mean + S.E. for four chicks expressed as picomoles of malonyl-CoA incorporated into long-chain fatty acids/min per mg protein. The incubation medium for both assays contained 90 mM KC1, 50 mM potassium phosphate buffer (pH 7"4), 1 mM EDTA, 5 mM MgCI2, 5 mM KCN, 5 mM NADPH and 0"3 mM 1- or 3-14C malonyl-CoA. The medium for the microsomal system also contained 10 mM ATP. The medium for fatty acid synthetase was the same as the medium for the microsomal system except that ATP w a s omitted and 39/~M unlabeled acetyl-CoA was added. The assays were for 20 min at 25°C. In another experiment, pure aflatoxin B1, even at the high concentration of 20/~g/ml of incubation medium, was without effect on the fatty acid synthetase activity of the 100,000 g supernatant fraction of liver from chicks not fed aflatoxin. The decreased incorporation in vivo of labeled acetate into the long-chain fatty acids of liver of chicks fed aflatoxin indicate that fatty acid synthesis is inhibited during aflatoxicosis. The decrease of fatty acid synthesis concomitant with an accumulation of lipid in liver (Smith & Hamilton, 1970) suggests strongly that the mobilization of hepatic lipids and/or the transport of these lipids to peripheral tissue are inhibited during aflatoxicosis. Shank & Wogan (1966) reached a similar conclusion after observing a decreased incorporation of labeled glucose into liver lipids concomitant with a rise in total lipid of the liver of ducklings. The reduced specific activity of fatty acid synthesizing enzymes in liver homogenates from chicks fed aflatoxin and the failure of aflatoxin to inhibit these enzymes when added to homogenates from chicks not fed aflatoxin suggest that aflatoxin exerts its effect on lipogenesis by depressing somehow the formation of the enzymes involved in fatty acid synthesis. A ready mechanism for such an inhibition exists in the studies of Clifford & Rees (1967), Pong & Wogan (1969) and Lafarge & Frayssinet (1970) who hypothesized that aflatoxin binds to D N A and thus interferes with RNA polymerase and subsequently with protein synthesis. However, such a simple and well-founded mechanism does not appear to explain the apparent specificity of the inhibition of lipid synthesis by aflatoxin, since the inhibitory doses are smaller than those required to inhibit growth (Smith & Hamilton, 1970). Lipid synthesis in human skin slices is reduced after only a few hours' incubation with aflatoxin (Black et al., 1970) and kinetic experiments with perfused rat liver revealed a cytotoxic effect before any effect on metabolism of blood proteins could be observed (John & Miller, 1969). In the chicken, lipid transport is altered by
846
W. E. DONALDSON,HsI-TANG TUNG and P. B. HAMILTON
smaller doses than are required to depress growth rate ( T u n g et al., 1971). Thus, the hypothesis of a general inhibition of R N A polymerase as a result of binding of aflatoxin to D N A would appear to need modification to allow for the specific inhibition of lipid synthesis and transport. Such a modification may reside in the findings and ideas of Lafarge & Frayssinet (1970) that the formation of long messenger R N A is more severely affected by aflatoxin than is the formation of short messenger RNA. I n any case, it would appear that further investigation into effects of aflatoxin on lipid metabolism and nucleic acid metabolism will be needed before a detailed understanding of aflatoxicosis is obtained.
Acknowledgements--This is Paper No. 3525 of the Journal Series of the North Carolina State University Agricultural Experiment Station, Raleigh, North Carolina. This research was supported in part by the U.S. Public Health Service, Grant No. HD-02887, National Institutes of Health. The technical assistance of Mrs. F. D. Suggs and Mr. C. Strickland is gratefully acknowledged. REFERENCES ASAO T., BUCHI G., ABHEL-KADERM. M., CHANG S. B., WICK E. L. & WOGAN G. N. (1970) Aflatoxins B and G. j% Am. Chem. Soc. 85, 1706-1707. BLACKH. S., SMITHJ. D., AUSTINB. J. & RAUSCHKOLBE. W. (1969) Effect of aflatoxin B1 on the in vitro incorporation of 14C-acetate into human skin lipids. Experientia 26, 1292-1293. CLELANDK. W. ~ SLATERE. C. (1953) Respiratory granules of heart muscle. Biochem. J. 53, 547-556. CLIFFORD J. I. ~ REES K. R. (1967) The action of aflatoxin BI on the rat liver. Biochem.J. 102, 65-75. DONALDSONW. E. (1967) Influence of biotin deficiency and dietary sterculic acid on fatty acid dehydrogenation. Biochem. biophys. Res. Commun. 26, 539-543. DONALDSONW. E., WIT-PEETERSE. M. & SCHOLTEH. R. (1970) Fatty acid synthesis in rat liver: relative contributions of the mitochondrial microsomal and non-particulate systems. Biochim. biophys. Acta 202, 35-42. JOHN D. W. & MILL~.R L. L. (1969) Effect of aflatoxin B1 on net synthesis of albumin, fibrinogen and a-1 acid glycoprotein by the isolated perfused rat liver. Biochem. Pharmac. 18, 1135-1146. KATO R., ONODAK. & OMORI Y. (1969) Effect of aflatoxin B1 on the incorporation of 14Cacetate into cholesterol by rat liver. Experientia 25, 1026. LAFARGE C. & FRAYSSINETC. (1970) The reversibility of inhibition of RNA and DNA synthesis induced by aflatoxin in rat liver. A tentative explanation for carcinogenic mechanism. Int..~. Cancer 6, 74-83. O'HEA E. K. & LEVEILLEG. A. (1969) Lipid biosynthesis and transport in the domestic chick (Gallus domesticus). Comp. Biochem. Physiol. 30, 149-159. PONG R. S. & WOGANG. N. (1969) Time course of alterations of rat liver polysome profiles induced by aflatoxin BI. Biochem. Pharmac. 18, 2357-2361. SHANKR. C. & WOGANG. N. (1966) Acute effects of aflatoxin B, on liver composition and metabolism in the rat and duckling. Toxic. Appl. Pharmacol. 9, 468-476. SMITH J. W. & HAMILTONP. n. (1970) Aflatoxicosis in the broiler chicken. Poult. Sci. 49, 207-215. TUNG H. T., DONALDSONW. E. &HAMILTONP. B. (1971) Altered lipid transport during aflatoxicosis. Toxicol. Appl. Pharmacol. (In press.)
DEPRESSION OF FATTY ACID SYNTHESIS I N CHICK LIVER BY AFLATOXIN
847
WOGAN G. N. & NEWBERNE P. M. (1967) Dose-response characteristics of aflatoxin Bt carcinogenesis in the rat. Cancer Res. 27, 2370-2376. Key Word Index--Gallus domesticus; microsomes; fatty acid synthesis; synthetase of fatty acids; aflatoxin; lipogenesis.