Influence of mercuric chloride on the metabolism and hepatotoxicity of bromobenzene in rats

Abstract

When male Sprague-Dawley rats were treated with 1 mg mercuric chloride (HgCl2)/kg, sc 6 hr prior to or simultaneously with a single 2.5-mmole/kg ip dose of bromobenzene and sacrificed 48 hr after the bromobenzene dose, the activities of serum transaminases (SGOT and SGPT) were found to be significantly reduced when compared with those obtained in bromobenzene-alone-treated rats. Similar phenomena were observed when rats were treated simultaneously with 1 or 2 mg HgCl2/kg and 1 mmole bromobenzene/kg, but not when bromobenzene was given 6 hr prior to HgCl2 injection. When 5 mmole bromobenzene/kg and 1 mg HgCl2/kg were given simultaneously to the animals, such an apparent reduction in bromobenzene toxicity was again observed. In each case, HgCl2 alone had no effect on the transaminase activities. HgCl2 (1 mg/kg, sc) treatment reduced the hepatic microsomal cytochrome P-450 content. Treatment with 1 mg HgCl2/kg 6 hr prior to bromobenzene injection (2.5 mmole/kg) significantly reduced the urinary excretion of para- and metabromophenols, and parabromocatechol during 0 to 24-hr period without affecting the urinary thioethers. These data suggest a possible reduction in the rate of formation of bromobenzene epoxide intermediate due to mercury pretreatment, resulting in a lowering of the steady state level of this epoxide so that an inhibition of hepatotoxicity due to bromobenzene could occur. However, simultaneous treatments of HgCl2 and bromobenzene failed to modify the urinary metabolic excretion pattern of bromobenzene. When rats were given 10, 50, and 100 ppm of HgCl2 in drinking water daily for 4 weeks prior to an ip injection of 2.5 mmole bromobenzene/kg and were sacrificed 48 hr after the dose, no changes in SGOT and SGPT activities were observed. These results indicate that changes in the metabolism and hepatotoxicity of bromobenzene due to mercury depend on (a) the dose and time of mercury administration, and (b) the mode of administration of mercury, acute or chronic.