Influence of zinc chloride on the metabolism and hepatotoxicity of bromobenzene in rats.

In studying the possible interactive effects of various heavy metals on bromobenzene hepatotoxicity and metabolism, zinc chloride (ZnCl2) (0.5, 2.0, and 10.0 mg/kg) was given ip 24 hr prior to ip administration of bromobenzene (2.5 mmol/kg body wt). Animals were sacrificed 48 hr after bromobenzene. A significant increase in the activities of serum transaminases (serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) was observed at 0.5 mg/kg ZnCl2 and such an effect was not observed at the two higher doses of ZnCl2. However, no such increase in the transaminases activities was observed when rats were treated with identical doses of ZnCl2 48 hr before the administration of bromobenzene. When rats were treated with 2 mg/kg ZnCl2 6 hr prior to the bromobenzene dose, a potentiation of the hepatotoxicity due to bromobenzene was again observed, whereas simultaneous treatment of bromobenzene and ZnCl2 produced no such effect. Treatment with ZnCl2 (0.5 mg/kg) 24 hr prior to bromobenzene injection failed to modify the pattern of the urinary metabolites of bromobenzene. When rats were given 50, 250, or 500 ppm of ZnCl2 in drinking water daily for 4 weeks prior to an ip injection of 2.5 mmol/kg bromobenzene, a reduction in the activities of serum transaminases was observed in 250 ppm ZnCl2-treated rats only. Such a reduction in the hepatotoxicity of bromobenzene is accompanied by a simultaneous reduction of the in vivo metabolism of bromobenzene by zinc, as substantiated by reduction of its urinary thioethers as well as of its total urinary metabolites. The present study has shown that changes in the metabolism and hepatotoxicity of bromobenzene depend on the dose of zinc administered, as well as on the temporal relationship between the zinc and bromobenzene administrations. The definitive mechanism responsible for such interactions remains to be elucidated.