Mutation Research, 28 (1975) 137-139 © Elsevier Scientific Publishing Company, Amsterdam--Printed in The Netherlands
137
Mutagenicity tests with aflatoxins in the mouse Introduction Aflatoxins, a collective term for eight compounds of related molecular configuration (i.e., aflatoxins BI, B2, B2a, GI, G2, G2a, MI, and M2), are metabolites of Aspergillus flavus, a common contaminant of stored human and animal foodstuffs (refs. I, 5, 24). Aflatoxin BI and GI are the most abundant and active compounds of this group. They are acutely hepatotoxic and have been shown to be potent carcinogens in the rat 4,7,15,2., and rainbow trout 3. Aflatoxin B I is known to inhibit protein synthesis and DNA-dependent RNA synthesise,~5,2s. Various types of genetic effects following aflatoxin treatment of whole organisms, or cells in culture, have been described in different organisms. Aflatoxin B I has been shown to be mutagenic in the Bacillus subtilis transforming DNA assay in vitro 19 and in Neurospora crassa2°, ~1. It inhibits the mitotic process in human embryonic lung cells 16 and produces chromosome aberrations in seedling roots of Vicia faba is, in Allium cepa 2~, in a cell line derived from the rat Kangaroo 12, and in human leucocytes in vitrog,22, 27. Aflatoxin B I is able to induce autosomal recessive-lethal mutations in Drosophila melanogaster ~4 whereas a mixture of aflatoxins B I and GI causes an increase in the dominant lethals in male mice 1°. In the present experiments the capacity of aflatoxin BI to produce heritable chromosomal changes in mice has been tested by analysing the spermatocyte I chromosomes of the treated males (spermatocyte test on treated males) and of their offspring (VI translocation test) 17. Material and methods Twenty five male mice from the BALB/c strain, 11-13 weeks old, received an i.p. injection of 5 mg/kg of aflatoxin B I (Makor Chemicals, Israel) dissolved in a mixture of saline and dimethylsulfoxide (DMSO) (I ml dimethylsulfoxide plus 9 ml 9% NaC1). This dose of aflatoxin B I was chosen on the basis of different experiments reported previously2,8, 2s. 8 h after treatment each male was mated to one virgin female of the same strain and received one fresh female per week for 5 weeks. Litter size was recorded at birth and the offspring were sexed at weaning 20 days later. The testes of the treated males and of their mature offspring were prepared b y the airdrying method of EVANS et al. n. IO control males given no treatment and IO animals receiving the saline solution of DMSO only were mated as previously described and their testes examined by the same technique. 20o dividing spermatocytes at the diakinesis-first metaphase stage of meiosis were examined for each treated animal and 25 cells for each F I male. Results and discussion Table I shows that the percentage of pregnant females in the treated group decreased consistently trom 64% on the first week of the mating to 36% on the fifth week (t =- 19.8; P < o . o o o i ) . The mean weight of the testes was, however, the same in each of the three groups (286 mg =L 9 rag) and no significant difference was observed between treated and control animals with respect to the mean litter size at Abbreviation: DMSO, dimethylsulfoxide.
138 TABLE SUMMARY
SHORT COMMUNICATIONS I OF FERTILITY
Observation
OF THE
AND CONTROLLED
A.flatoxin B t 1St week 2rid week 3rd week
Total females 25 Pregnant females Total 16 ~}~ 64 Offspring at birth Total ~ o3 L i t t e r size 6. 4 Offspring at the weaning Total 9r L i t t e r size 5.7
TABLE
TREATED
MALES
D31NO 4th week
5th week
25
25
25
25
t5 60
12
IO
9
48
4°
36
~4 5.6
7° 5,8
67 6- 7
7° 4.7
63 5.2
Oo 6.0
Control
5°
5°
33 66.0
34 68.o
57 6.3
22~ 6.7
2-I 0. 5
5° 5.6
19I 5.8
07 5.S
[1
CYTOLOGICAL
OBSERVATIONS
Treatment
Test Spermatocyte
test on treated males
I?i t r a n s l o c a t i o n
test
Control 1)MSO Aflatoxin B1 Aflatoxin BI
A nimals examined Io Io 2.5 I85
Total cells analysed
Cells with anomalies
2ooo 2ooo 500o 4625
I (CIV) o i (CIV) o
birth or at weaning. These results, as well as the observations of HINTZ et al. la who found no effect on the reproduction of swine fed a diet containing 45o ppm aflatoxin B I , suggest that the prenatal lethality is not increased by administration of aflatoxin BI to male mammals. The positive findings of EPSTEIN AND SCHAFNER 1~, who reported an increase of dominant lethal mutations following injection of mice with a mixture of aflatoxins BI and GI in dimethylsulioxide suspension, might be explained by the fact that the number of pregnant females (seven) dissected was small and that the dose of aflatoxin was very high (68 mg/kg)! The results of cytological examinations are summarized in Table I I. No chromosome rearrangement was detected in the treated males (spermatocyte test on treated males) nor in their male offspring (FI translocation test). Our results indicate therefore that aflatoxin BI given at a dose of 5 mg/kg body weight does not produce gross structural chromosome changes in male mouse germ cells. Since this compound has been demonstrated to be mutagenic in different systems 19-21 and to produce chromosome aberrations in plant ro.aterialla, 2a and in mammalian chromosomes in vitro", 12,~2,2~ the absence of nmtagenic effects in vivo could possibly be explained by a low penetration in tb.e testes or by its metabolic degradation 26. This work was supported in part by grants from tile Fonds de la Recherche Scientifique Fondamentale Collective.
Laboratory of Genetics, Department of Radiobiology, C.E.N./S.C.K. B-z4oo, Mol (Belgium)
A. LEONARD (;H. DEKNUDT (~. L I N D E N
SHORT COMMUNICATIONS
139
I ALLCROFT, :R., A s p e c t s of aflatoxicosis in f a r m a n i m a l s , in G. Iq. WOGAN (Ed.), Mycotoxins in Foodstuffs, M.I.T., C a m b r i d g e , 1965, pp. 153-162. 2 ARMBRECHT, B. H., AND W. T. SHALKOP, T h e effects of D D T a n d aflatoxin p r i m i n g on t h e a c u t e aflatoxin t o x i c i t y in r a m s , Environ. Physiol. Biochem., 2 (1972) 3-6. 3 ASHLEY, L. M., J. E. HALVER AND G. N. WOGAN, H e p a t o m a a n d aflatoxicosis in t r o u t , Fed. Proc., 23 (1964) IO5-IIO. 4 BARNES, J. M., AND W. H. BUTLER, Carcinogenic a c t i v i t y of aflatoxin to rats, Nature, 202 (1954) lO16. 5 BURNSIDE, J. E., W. L. SIPPEL, J. FORGAES, W. T. CARLL, M. B. ATWOOD AND ~. 1:{. DOLL, A disease of swine a n d cattle c a u s e d b y e a t i n g m o l d y corn, II. E x p e r i m e n t a l p r o d u c t i o n w i t h p u r e c u l t u r e s of molds, Am. J. Vet. Res., 18 (1957) 817-824. 6 CLIFFORD, J. I., AND K. R. REES, A f l a t o x i n : a site of a c t i o n in t h e r a t liver cell, Nature, 209 (1966) 312-313 . 7 DICKENS, F., AND H. E. H. JONES, T h e carcinogenic action of aflatoxin a f t e r its s u b c u t a n e o u s injection in t h e rat, Brit. J. Cancer, 17 (1963) 691-698. 8 DIPAOLO, J. A., J. ELls AND H. ERWlN, T e r a t o g e n i c response b y h a m s t e r s , r a t s a n d mice to a f l a t o x i n B I , Nature, 215 (1967) 638 639. 9 DOLIMPIO, D. A., C. JACOBSON AND M. S. LEGATOR, Effect of aflatoxin on h u m a n leucocytes, Proc. Soc. Exptl. Biol, Med., 127 (1968) 559-562. IO EPSTEIN, S. S., AND H. SCHAFNER, Chemical m u t a g e n s in t h e h u m a n e n v i r o n m e n t , Nature, 219 (1968) 385-387 . I I EVANS, E. P., G. BRECKON AND C. E. FORD, An a i r - d r y i n g m e t h o d for meiotic p r e p a r a t i o n from m a m m a l i a n testes, Cytogenetics, 3 (1964) 289-294. 12 GREEN, S., M. LEGATOR AND C, JACOBSON, Utilization of a cell line derived f r o m r a t k a n g a r o o for c y t o g e n e t i c studies, Mammalian Chromosome Newsletter, 8 (1967) 36. 13 HINTZ, H. V., H. HEITMAN, A. •. BOOTH AND W. E. GAGNE, Effects of aflatoxin on r e p r o d u c tion in swine, Proc. Soc. Exptl. Biol. ,~/Ied., 126 (1967) 146-148. 14 LAMB, M. J., AND L. J. LILLY, I n d u c t i o n of recessive lethals in Drosophila melanogaster b y aflatoxin B I , Mutation Res., I1 (1971) 43o-433. 15 LANCASTER, M. C., F. P. JENKINS AND J. M. PHILP, T o x i c i t y a s s o c i a t e d w i t h c e r t a i n s a m p l e s of g r o u n d n u t s , Nature, 192 (1961) lO95-1o96. 16 LEGATOR, M. S., AND A. WITHROW, Aflatoxin : Effect on m i t o t i c division in c u l t u r e d e m b r y o n i c l u n g cells, J. Assoc. Offic. Agr. Chemists, 47 (1964) lOO7-1oo9. 17 LEONARD, A., O b s e r v a t i o n s on meiotic c h r o m o s o m e s of t h e m a l e m o u s e as a t e s t of t h e p o t e n tial m u t a g e n i c i t y of c h e m i c a l s in m a m m a l s , in A. HOLLAENDER (Ed.), Chemical Mutagens: Principles and Methods for their Detection, Vol. 3, P l e n u m , N e w York, 1973, pp- 21-56. 18 LILLY, L. J., I n d u c t i o n of c h r o m o s o m e a b e r r a t i o n s b y aflatoxin, Nature, 207 (1965) 433-434. 19 MAHER, V. M., AND W. C. SUMMERS, M u t a g e n i c action of aflatoxin BI on t r a n s f o r m i n g D N A a n d inhibition of D N A t e m p l a t e a c t i v i t y in vitro, Nature, 225 (197 o) 68-7o. 2o ONG, T., M u t a g e n i c i t y of aflatoxins in Neurospora crassa, Mutation Res., 9 (197 o) 615-618. 21 ONG, T., M u t a g e n i c activities of aflatoxin B I a n d GI in Neurospora crassa, Mol. Gen. Genet., i i i (1971 ) 159-17o. 22 PROMCHAINANT, C., V. BAIMAI AND A. NONDASUTA, T h e c y t o g e n e t i c effects of aflatoxin a n d g a m m a - r a y s on h u m a n leucocytes in vitro, Mutation Res., 16 (1972) 373-380. 23 REISS, J., C h r o m o s o m e n a b e r r a t i o n e n in d e n W u r z e l s p i t z e n y o n Mllium cepa d u r c h A f l a t o x i n B I , Experientia, 27 (1971) 971-972. 24 SARGEANT, K., A. SHERIDAN, J. O'KELLY AND R. B. A. CARNAGHAN, T o x i c i t y associated w i t h c e r t a i n s a m p l e s of g r o u n d n u t s , Nature, 192 (1961) lO96-1o97. 25 SPORN, M. B., C. W. DINGMAN, H. L. PHELPS AND G. N. SOGAN, Aflatoxin B I : b i n d i n g to D N A in vitro a n d a l t e r a t i o n of R N A m e t a b o l i s m in vivo, Science, 151 (1966) 1539-1541. 26 STEYN, M., M. J. PITOUT AND I. F. H. PURCHASE, A c o m p a r a t i v e s t u d y on aflatoxin B I m e t a b o l i s m in mice a n d rats, Brit. J. Cancer, 25 (1971) 291-297. 27 WITHERS, R. F. J., T h e a c t i o n of s o m e lactones a n d related c o m p o u n d s on h u m a n c h r o m osomes, in Z. LANDA (Ed.), Proceedings of the Symposium on the Mutational Process, Prague, 1965 , Czechoslovakia A c a d e m y of Sciences, 1966, pp. 359-364 . 28 WO6AN, G. N., Chemical n a t u r e a n d biological effects of t h e aflatoxins, Bacteriol. Rev., 3 ° (1966) 46o-470. Received
July 9th, 1974
137
Mutagenicity tests with aflatoxins in the mouse Introduction Aflatoxins, a collective term for eight compounds of related molecular configuration (i.e., aflatoxins BI, B2, B2a, GI, G2, G2a, MI, and M2), are metabolites of Aspergillus flavus, a common contaminant of stored human and animal foodstuffs (refs. I, 5, 24). Aflatoxin BI and GI are the most abundant and active compounds of this group. They are acutely hepatotoxic and have been shown to be potent carcinogens in the rat 4,7,15,2., and rainbow trout 3. Aflatoxin B I is known to inhibit protein synthesis and DNA-dependent RNA synthesise,~5,2s. Various types of genetic effects following aflatoxin treatment of whole organisms, or cells in culture, have been described in different organisms. Aflatoxin B I has been shown to be mutagenic in the Bacillus subtilis transforming DNA assay in vitro 19 and in Neurospora crassa2°, ~1. It inhibits the mitotic process in human embryonic lung cells 16 and produces chromosome aberrations in seedling roots of Vicia faba is, in Allium cepa 2~, in a cell line derived from the rat Kangaroo 12, and in human leucocytes in vitrog,22, 27. Aflatoxin B I is able to induce autosomal recessive-lethal mutations in Drosophila melanogaster ~4 whereas a mixture of aflatoxins B I and GI causes an increase in the dominant lethals in male mice 1°. In the present experiments the capacity of aflatoxin BI to produce heritable chromosomal changes in mice has been tested by analysing the spermatocyte I chromosomes of the treated males (spermatocyte test on treated males) and of their offspring (VI translocation test) 17. Material and methods Twenty five male mice from the BALB/c strain, 11-13 weeks old, received an i.p. injection of 5 mg/kg of aflatoxin B I (Makor Chemicals, Israel) dissolved in a mixture of saline and dimethylsulfoxide (DMSO) (I ml dimethylsulfoxide plus 9 ml 9% NaC1). This dose of aflatoxin B I was chosen on the basis of different experiments reported previously2,8, 2s. 8 h after treatment each male was mated to one virgin female of the same strain and received one fresh female per week for 5 weeks. Litter size was recorded at birth and the offspring were sexed at weaning 20 days later. The testes of the treated males and of their mature offspring were prepared b y the airdrying method of EVANS et al. n. IO control males given no treatment and IO animals receiving the saline solution of DMSO only were mated as previously described and their testes examined by the same technique. 20o dividing spermatocytes at the diakinesis-first metaphase stage of meiosis were examined for each treated animal and 25 cells for each F I male. Results and discussion Table I shows that the percentage of pregnant females in the treated group decreased consistently trom 64% on the first week of the mating to 36% on the fifth week (t =- 19.8; P < o . o o o i ) . The mean weight of the testes was, however, the same in each of the three groups (286 mg =L 9 rag) and no significant difference was observed between treated and control animals with respect to the mean litter size at Abbreviation: DMSO, dimethylsulfoxide.
138 TABLE SUMMARY
SHORT COMMUNICATIONS I OF FERTILITY
Observation
OF THE
AND CONTROLLED
A.flatoxin B t 1St week 2rid week 3rd week
Total females 25 Pregnant females Total 16 ~}~ 64 Offspring at birth Total ~ o3 L i t t e r size 6. 4 Offspring at the weaning Total 9r L i t t e r size 5.7
TABLE
TREATED
MALES
D31NO 4th week
5th week
25
25
25
25
t5 60
12
IO
9
48
4°
36
~4 5.6
7° 5,8
67 6- 7
7° 4.7
63 5.2
Oo 6.0
Control
5°
5°
33 66.0
34 68.o
57 6.3
22~ 6.7
2-I 0. 5
5° 5.6
19I 5.8
07 5.S
[1
CYTOLOGICAL
OBSERVATIONS
Treatment
Test Spermatocyte
test on treated males
I?i t r a n s l o c a t i o n
test
Control 1)MSO Aflatoxin B1 Aflatoxin BI
A nimals examined Io Io 2.5 I85
Total cells analysed
Cells with anomalies
2ooo 2ooo 500o 4625
I (CIV) o i (CIV) o
birth or at weaning. These results, as well as the observations of HINTZ et al. la who found no effect on the reproduction of swine fed a diet containing 45o ppm aflatoxin B I , suggest that the prenatal lethality is not increased by administration of aflatoxin BI to male mammals. The positive findings of EPSTEIN AND SCHAFNER 1~, who reported an increase of dominant lethal mutations following injection of mice with a mixture of aflatoxins BI and GI in dimethylsulioxide suspension, might be explained by the fact that the number of pregnant females (seven) dissected was small and that the dose of aflatoxin was very high (68 mg/kg)! The results of cytological examinations are summarized in Table I I. No chromosome rearrangement was detected in the treated males (spermatocyte test on treated males) nor in their male offspring (FI translocation test). Our results indicate therefore that aflatoxin BI given at a dose of 5 mg/kg body weight does not produce gross structural chromosome changes in male mouse germ cells. Since this compound has been demonstrated to be mutagenic in different systems 19-21 and to produce chromosome aberrations in plant ro.aterialla, 2a and in mammalian chromosomes in vitro", 12,~2,2~ the absence of nmtagenic effects in vivo could possibly be explained by a low penetration in tb.e testes or by its metabolic degradation 26. This work was supported in part by grants from tile Fonds de la Recherche Scientifique Fondamentale Collective.
Laboratory of Genetics, Department of Radiobiology, C.E.N./S.C.K. B-z4oo, Mol (Belgium)
A. LEONARD (;H. DEKNUDT (~. L I N D E N
SHORT COMMUNICATIONS
139
I ALLCROFT, :R., A s p e c t s of aflatoxicosis in f a r m a n i m a l s , in G. Iq. WOGAN (Ed.), Mycotoxins in Foodstuffs, M.I.T., C a m b r i d g e , 1965, pp. 153-162. 2 ARMBRECHT, B. H., AND W. T. SHALKOP, T h e effects of D D T a n d aflatoxin p r i m i n g on t h e a c u t e aflatoxin t o x i c i t y in r a m s , Environ. Physiol. Biochem., 2 (1972) 3-6. 3 ASHLEY, L. M., J. E. HALVER AND G. N. WOGAN, H e p a t o m a a n d aflatoxicosis in t r o u t , Fed. Proc., 23 (1964) IO5-IIO. 4 BARNES, J. M., AND W. H. BUTLER, Carcinogenic a c t i v i t y of aflatoxin to rats, Nature, 202 (1954) lO16. 5 BURNSIDE, J. E., W. L. SIPPEL, J. FORGAES, W. T. CARLL, M. B. ATWOOD AND ~. 1:{. DOLL, A disease of swine a n d cattle c a u s e d b y e a t i n g m o l d y corn, II. E x p e r i m e n t a l p r o d u c t i o n w i t h p u r e c u l t u r e s of molds, Am. J. Vet. Res., 18 (1957) 817-824. 6 CLIFFORD, J. I., AND K. R. REES, A f l a t o x i n : a site of a c t i o n in t h e r a t liver cell, Nature, 209 (1966) 312-313 . 7 DICKENS, F., AND H. E. H. JONES, T h e carcinogenic action of aflatoxin a f t e r its s u b c u t a n e o u s injection in t h e rat, Brit. J. Cancer, 17 (1963) 691-698. 8 DIPAOLO, J. A., J. ELls AND H. ERWlN, T e r a t o g e n i c response b y h a m s t e r s , r a t s a n d mice to a f l a t o x i n B I , Nature, 215 (1967) 638 639. 9 DOLIMPIO, D. A., C. JACOBSON AND M. S. LEGATOR, Effect of aflatoxin on h u m a n leucocytes, Proc. Soc. Exptl. Biol, Med., 127 (1968) 559-562. IO EPSTEIN, S. S., AND H. SCHAFNER, Chemical m u t a g e n s in t h e h u m a n e n v i r o n m e n t , Nature, 219 (1968) 385-387 . I I EVANS, E. P., G. BRECKON AND C. E. FORD, An a i r - d r y i n g m e t h o d for meiotic p r e p a r a t i o n from m a m m a l i a n testes, Cytogenetics, 3 (1964) 289-294. 12 GREEN, S., M. LEGATOR AND C, JACOBSON, Utilization of a cell line derived f r o m r a t k a n g a r o o for c y t o g e n e t i c studies, Mammalian Chromosome Newsletter, 8 (1967) 36. 13 HINTZ, H. V., H. HEITMAN, A. •. BOOTH AND W. E. GAGNE, Effects of aflatoxin on r e p r o d u c tion in swine, Proc. Soc. Exptl. Biol. ,~/Ied., 126 (1967) 146-148. 14 LAMB, M. J., AND L. J. LILLY, I n d u c t i o n of recessive lethals in Drosophila melanogaster b y aflatoxin B I , Mutation Res., I1 (1971) 43o-433. 15 LANCASTER, M. C., F. P. JENKINS AND J. M. PHILP, T o x i c i t y a s s o c i a t e d w i t h c e r t a i n s a m p l e s of g r o u n d n u t s , Nature, 192 (1961) lO95-1o96. 16 LEGATOR, M. S., AND A. WITHROW, Aflatoxin : Effect on m i t o t i c division in c u l t u r e d e m b r y o n i c l u n g cells, J. Assoc. Offic. Agr. Chemists, 47 (1964) lOO7-1oo9. 17 LEONARD, A., O b s e r v a t i o n s on meiotic c h r o m o s o m e s of t h e m a l e m o u s e as a t e s t of t h e p o t e n tial m u t a g e n i c i t y of c h e m i c a l s in m a m m a l s , in A. HOLLAENDER (Ed.), Chemical Mutagens: Principles and Methods for their Detection, Vol. 3, P l e n u m , N e w York, 1973, pp- 21-56. 18 LILLY, L. J., I n d u c t i o n of c h r o m o s o m e a b e r r a t i o n s b y aflatoxin, Nature, 207 (1965) 433-434. 19 MAHER, V. M., AND W. C. SUMMERS, M u t a g e n i c action of aflatoxin BI on t r a n s f o r m i n g D N A a n d inhibition of D N A t e m p l a t e a c t i v i t y in vitro, Nature, 225 (197 o) 68-7o. 2o ONG, T., M u t a g e n i c i t y of aflatoxins in Neurospora crassa, Mutation Res., 9 (197 o) 615-618. 21 ONG, T., M u t a g e n i c activities of aflatoxin B I a n d GI in Neurospora crassa, Mol. Gen. Genet., i i i (1971 ) 159-17o. 22 PROMCHAINANT, C., V. BAIMAI AND A. NONDASUTA, T h e c y t o g e n e t i c effects of aflatoxin a n d g a m m a - r a y s on h u m a n leucocytes in vitro, Mutation Res., 16 (1972) 373-380. 23 REISS, J., C h r o m o s o m e n a b e r r a t i o n e n in d e n W u r z e l s p i t z e n y o n Mllium cepa d u r c h A f l a t o x i n B I , Experientia, 27 (1971) 971-972. 24 SARGEANT, K., A. SHERIDAN, J. O'KELLY AND R. B. A. CARNAGHAN, T o x i c i t y associated w i t h c e r t a i n s a m p l e s of g r o u n d n u t s , Nature, 192 (1961) lO96-1o97. 25 SPORN, M. B., C. W. DINGMAN, H. L. PHELPS AND G. N. SOGAN, Aflatoxin B I : b i n d i n g to D N A in vitro a n d a l t e r a t i o n of R N A m e t a b o l i s m in vivo, Science, 151 (1966) 1539-1541. 26 STEYN, M., M. J. PITOUT AND I. F. H. PURCHASE, A c o m p a r a t i v e s t u d y on aflatoxin B I m e t a b o l i s m in mice a n d rats, Brit. J. Cancer, 25 (1971) 291-297. 27 WITHERS, R. F. J., T h e a c t i o n of s o m e lactones a n d related c o m p o u n d s on h u m a n c h r o m osomes, in Z. LANDA (Ed.), Proceedings of the Symposium on the Mutational Process, Prague, 1965 , Czechoslovakia A c a d e m y of Sciences, 1966, pp. 359-364 . 28 WO6AN, G. N., Chemical n a t u r e a n d biological effects of t h e aflatoxins, Bacteriol. Rev., 3 ° (1966) 46o-470. Received
July 9th, 1974
