Sex differences in monochloroacetate pretreatment effects on chloroform toxicity in rats

Previous studies have shown that dichloroacetate and trichloroacetate increase the toxicity of CHCl3. The present experiments were designed to determine if monochloroacetate (MCA) similarly affects CHCl3 toxicity. There were occasional differences, but overall kidney function indices (urine volume, osmolality and electrolyte concentration, glucosuria, retention of urea nitrogen in plasma) were not affected differently at either 24 or 48 hr after CHCl3 in saline and MCA pretreated Sprague-Dawley rats of either sex. Males pretreated with MCA had 45-fold greater plasma alanine aminotransferase (ALT) compared to the saline pretreated group similarly dosed with CHCl3. ALT was increased threefold in female rats, a modest change that suggests hepatic damage, and BUN was nonsignificantly increased. Therefore hepatic and renal functions were assessed in females. MCA pretreatment did not alter the effects of CHCl3 on hepatic excretory function or glomerular or tubular function. Bile production and glomerular filtration were both decreased in the MCA group treated with peanut oil, suggesting that MCA impairs both liver and kidney function in female rats. MCA pretreatment increases CHCl3 hepatoxicity markedly in male rats and only slightly in female rats. This difference is likely due to the different effects, in males and females, of MCA on the cytochrome P450 isoforms that activate CHCl3. The effects of MCA on renal function in females would decrease CHCl3 delivery to kidney cells, suggesting that MCA may alter the distribution of CHCl3.