121
Mutation Research, 65 (1979) 121--131 © Elsevier/North-Holland Biomedical Press
THE MUTAGENICITY
OF TRIMETHYLPHOSPHATE
T.H. CONNOR
University of Texas Medical Branch, Galveston, TX (U.S.A.) (Received 17 November 1978) (Accepted 23 January 1979)
Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical and physieal properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biotransformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Toxicology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Acute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Chronic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carcinogenieity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mutagenieity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Microbial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Drosophila . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Chromosomal studies in cultured cells . . . . . . . . . . . . . . . . . . . . . . . . . . . D. Chromosomal studies in laboratory animals . . . . . . . . . . . . . . . . . . . . . . . E. Micronucleus test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F. Dominant lethal mutations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Sterility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
121 121 122 123 123 123 123 124 124 125 125 126 126 127 128 129 130 130
Introduction Trimethylphosphate ( T M P ) w a s i n t r o d u c e d as a f u e l a d d i t i v e f o r a l t e r i n g t h e e f f e c t s o f e n g i n e d e p o s i t s in 1 9 4 7 . I t is u s e d m a i n l y as a g a s o l i n e a d d i t i v e f o r c o n t r o l l i n g s u r f a c e i g n i t i o n a n d s p a r k - p l u g f o u l i n g [ 1 9 ] . I n i n d u s t r y , i t is u s e d as a m e t h y l a t i n g a g e n t [ 3 ] a n d a l s o as a c a t a l y s t in t h e p r e p a r a t i o n o f r e s i n s a n d p o l y m e r s . A l s o , i t is e m p l o y e d as a f l a m e r e t a r d a n t in p a i n t s a n d p o l y m e r s [19]. Chemical and physical properties Trimethylphosphate is t h e t r i m e t h y l e s t e r o f p h o s p h o r i c a c i d . I t h a s a m o l e c u l a r w e i g h t o f 1 4 0 . 0 9 . I t is a l i q u i d a t r o o m t e m p e r a t u r e , is f r e e l y s o l u b l e i n w a t e r , a n d is s t a b l e i n a q u e o u s s o l u t i o n [ 2 2 ] .
122
TMP and other phosphoric acid esters have been reported to react with DNA by Rozenkranz and Rosenkranz [ 28]. This was demonstrated by a reduction in the sedimentation coefficient after incubation of calf-thymus DNA with the esters. Ehrenberg et al. [11] demonstrated that TMP has approximately the same substrate constant as dimethylsulfate, methyl methanesulfate (MMS) and methyl bromide, although TMP is less reactive than the other three methylating compounds. In a study of alkylating activity of paired compounds, Bedford [2], reported that TMP is more reactive than triethylphosphate and the mutagenicity in Saccharomyces cerevisiae parallels the chemical reactivity. Biotransformation Jones, using 3:P-labelled TMP was able to demonstrate the presence of dimethylphosphate (DMP) in the urine of mice and rats treated orally or intraperitoneally [21]. Studies of 3:p-labelled DMP show that it is excreted unchanged and does n o t appear to be further metabolized to mono-alkyl phosphate or phosphoric acid [20,21]. Studies with [14C]TMP revealed two additional urinary metabolites, S-methylcysteine and its N-acetate. This indicates that TMP acts in this instance in an alkylating capacity [21]. In vitro, TMP reacts with glutathione to produce DMP and S-methylglutathione which is the in vivo precursor of S-methylcysteine [21] (Fig. 1).
CHsO\ 2
c"3°,, 2
cù3o2"o0ù3 TMP
Mutation Research, 65 (1979) 121--131 © Elsevier/North-Holland Biomedical Press
THE MUTAGENICITY
OF TRIMETHYLPHOSPHATE
T.H. CONNOR
University of Texas Medical Branch, Galveston, TX (U.S.A.) (Received 17 November 1978) (Accepted 23 January 1979)
Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Chemical and physieal properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Biotransformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Toxicology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Acute . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Chronic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carcinogenieity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Mutagenieity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A. Microbial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B. Drosophila . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C. Chromosomal studies in cultured cells . . . . . . . . . . . . . . . . . . . . . . . . . . . D. Chromosomal studies in laboratory animals . . . . . . . . . . . . . . . . . . . . . . . E. Micronucleus test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F. Dominant lethal mutations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . G. Sterility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Discussion and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
121 121 122 123 123 123 123 124 124 125 125 126 126 127 128 129 130 130
Introduction Trimethylphosphate ( T M P ) w a s i n t r o d u c e d as a f u e l a d d i t i v e f o r a l t e r i n g t h e e f f e c t s o f e n g i n e d e p o s i t s in 1 9 4 7 . I t is u s e d m a i n l y as a g a s o l i n e a d d i t i v e f o r c o n t r o l l i n g s u r f a c e i g n i t i o n a n d s p a r k - p l u g f o u l i n g [ 1 9 ] . I n i n d u s t r y , i t is u s e d as a m e t h y l a t i n g a g e n t [ 3 ] a n d a l s o as a c a t a l y s t in t h e p r e p a r a t i o n o f r e s i n s a n d p o l y m e r s . A l s o , i t is e m p l o y e d as a f l a m e r e t a r d a n t in p a i n t s a n d p o l y m e r s [19]. Chemical and physical properties Trimethylphosphate is t h e t r i m e t h y l e s t e r o f p h o s p h o r i c a c i d . I t h a s a m o l e c u l a r w e i g h t o f 1 4 0 . 0 9 . I t is a l i q u i d a t r o o m t e m p e r a t u r e , is f r e e l y s o l u b l e i n w a t e r , a n d is s t a b l e i n a q u e o u s s o l u t i o n [ 2 2 ] .
122
TMP and other phosphoric acid esters have been reported to react with DNA by Rozenkranz and Rosenkranz [ 28]. This was demonstrated by a reduction in the sedimentation coefficient after incubation of calf-thymus DNA with the esters. Ehrenberg et al. [11] demonstrated that TMP has approximately the same substrate constant as dimethylsulfate, methyl methanesulfate (MMS) and methyl bromide, although TMP is less reactive than the other three methylating compounds. In a study of alkylating activity of paired compounds, Bedford [2], reported that TMP is more reactive than triethylphosphate and the mutagenicity in Saccharomyces cerevisiae parallels the chemical reactivity. Biotransformation Jones, using 3:P-labelled TMP was able to demonstrate the presence of dimethylphosphate (DMP) in the urine of mice and rats treated orally or intraperitoneally [21]. Studies of 3:p-labelled DMP show that it is excreted unchanged and does n o t appear to be further metabolized to mono-alkyl phosphate or phosphoric acid [20,21]. Studies with [14C]TMP revealed two additional urinary metabolites, S-methylcysteine and its N-acetate. This indicates that TMP acts in this instance in an alkylating capacity [21]. In vitro, TMP reacts with glutathione to produce DMP and S-methylglutathione which is the in vivo precursor of S-methylcysteine [21] (Fig. 1).
CHsO\ 2
c"3°,, 2
cù3o2"o0ù3 TMP
