Studies on mercapturic acid synthesis by humans

Differences in urinary monochlorobenzene metabolites between rats and humans

The high performance liquid chromatographic method for the determination of p-chlorobenzene mercapturic acid and 4-chlorocatechol conjugates is described. For determination of urinary mercapturic acid, the benzene extract from urine was injected into a liquid chromatograph and for determination of urinary 4-chlorocatechol conjugates, hydrolysate was dissolved in methanol. The methanol solution containing 4-chlorocatechol was injected into a liquid chromatograph. Differences in urinary excretion of monochlorobenzene between rats and humans were studied. Monochlorobenzene was administered to rats intraperitoneally, and to humans orally or by inhalation. Urinary p-chlorophenylmercapturic acid, and 4-chlorocatechol after hydrolysis of its conjugate, were measured. The amount of total metabolites is proportional to the doses administered to rats, rabbits and mice by intraperitoneal injection. The ratio of urinary mercapturic acid to 4-chlorocatechol is in the order of rats, mice and rabbits by intraperitoneal injection, and rats and human beings by oral administration. The excretion of p-chlorophenylmercapturic acid was markedly less than that of 4-chlorocatechol in humans who received monochlorobenzene orally or by inhalation. The results indicate that the 4-chlorocatechol conjugate is a suitable index of metabolites in the urine of workers exposed to monochlorobenzene.