Kogo Hiraga

On the mechanism of butylated hydroxytoluene-induced hepatic toxicity in rats

The relations between serum transaminase activity and the hepatic contents of glutathione and lipid peroxide were examined following oral administration to rats of butylated hydroxytoluene (BHT; 500 or 1000 mg/kg). The glutathione level rapidly diminished and reached a minimum at 6 hr after BHT administration. The period of depletion was dependent on dose: restoration of the glutathione level took longer in high-dose rats than in low-dose rats. The content of hepatic lipid peroxide was not markedly changed by BHT throughout the experimental period. The activity of glutathione S-transferase was not affected until 12 hr after BHT administration but, thereafter, it increased with time and was accompanied by elevation of the glutathione level. Though the activities of serum glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase were not affected by low-dose BHT, they increased rapidly in the high-dose rates after a lag period of about 6 hr and reached a maximum at 24 hr after administration; at that time, the livers of the high-dose rats showed centrilobular necrosis. The results indicate that acute hepatic injury was induced by the high-dose BHT. Pretreatment with cobaltous chloride inhibited the increase in the activities of the serum transaminases produced by the high-dose of BHT accompanying the depletion of microsomal cytochrome P-450 content and the induction of glutathione content. These observations suggest that hepatic damage was associated with prolonged depletion of glutathione rather than with lipid peroxidation in the liver, and that the activated metabolites of BHT rather than the parent compound induced the tissue damage.

Induction of chromosome aberrations and sister-chromatid exchanges in CHO-K1 cells by o-phenylphenol

o-Phenylphenol (OPP), is used in Japan as a fungicide in food additives for citrus fruits. The induction of chromosome aberrations and sister-chromatid exchanges (SCEs) by OPP in cultured Chinese hamster ovary (CHO-K1) cells was studied. Cells were exposed to various concentrations of OPP ranging from 50 to 175 micrograms/ml for 3 h, and further incubated for 27 and 42 h. These incubation periods are almost equal to 2 and 3 cell cycles. SCEs and chromosome aberrations were induced by OPP at concentrations of 100, 125 and 150 micrograms/ml after the incubation for 27 h. For chromosome aberrations, chromatid breaks and exchanges there was a dose-dependent increase. Diplochromosomes due to endoreduplication were also caused by the same concentrations of OPP in a dose-dependent manner. After incubation for 42 h, chromosome aberrations were also increased by OPP at concentrations of 100 and 125 micrograms/ml, but the frequencies of SCEs were not significantly different from those of the control. These results suggest that OPP has a cytogenetic toxicity, and that the DNA damage resulting in SCEs induced by OPP is relatively short-lived and can be repaired during the longer incubation time.

Testicular atrophy induced by di-2-ethylhexyl phthalate: Effect of zinc supplement

The administration of di-2-ethylhexyl phthalate (DEHP) to young male rats was found to cause testicular atrophy and loss of testicular zinc. In an attempt to test the hypothesis that a cause and effect relationship exists between DEHP-induced loss of testicular zinc and testicular injury, zinc was coadministered (by ip injection or by dietary supplementation) with DEHP (po) for 10 days and organ weights and zinc concentrations were then measured. This testicular atrophy was not prevented by coadministration of zinc. The zinc concentration in the testis was not increased by zinc supplement despite increases in zinc concentrations in liver and serum. The results suggest that the toxic effect of DEHP on the testis may not result from an interference with gastrointestinal absorption of zinc.

Orthophenylphenol mutagenicity in a human cell strain.

Orthophenylphenol (OPP), a widely used fungicide, induced ouabain-resistant (OuaR) mutants in a ultraviolet (UV)-sensitive human RSa cell strain and the frequencies increased in a dose-related fashion. OPP was a more potent mutagen than UV at doses related to equal survival. These results suggest that OPP has a mutagenic activity and that further experiments on this chemical are warranted.

Strain differences in butylated hydroxytoluene-induced deaths in male mice

Abstract LD50 values (ip) for butylated hydroxytoluene (BHT) were compared in four strains of inbred and one strain of noninbred mice. The DBA 2N strain had a low LD50 value (138 mg/kg) and a steep slope in the regression line of its dose-mortality curve. In contrast, the LD50 value for the BALB c AnN strain was conspicuously higher (1739 mg/kg), whereas the regression line slope was parallel to that of the DBA 2N strain. The LD50 values for a strain of inbred mice ( C57BL 6N ) and a strain of noninbred mice (ICR-JCL) were 917 and 1243 mg/kg, respectively, and the slope of their regression lines was undramatic. The LD50 value and the slope for the AKR strain were between those of the above-mentioned strains. However, irres-ective of strain or dose level, death, if it occurred, was within 4 to 6 days after administration of BHT and was accompanied by massive edema and hemorrhage in the lung.

Vitamin K content of liver and feces from vitamin K-deficient and butylated hydroxytoluene (BHT)-treated male rats.

Vitamin K content of liver and feces from male rats fed diets containing butylated hydroxytoluene (BHT) was estimated by a chick bioassay method to investigate the mechanism of BHT-induced decreases in the activities of vitamin K-dependent clotting factors. The concentration of vitamin K in the liver of rats receiving BHT was reduced as compared to that of control rats. Conversely, the concentration of vitamin K in the feces from rats receiving BHT increased more than that from control rats. The vitamin K deficiency induced by BHT might be due to effects of BHT on absorption and excretion of vitamin K.