The urinary excretion of mercapturic acids after administration of bromobenzene and 3,4-benzpyrene.

In a previous communication (1) it was shown that the rat forms some mercapturic acid from simultaneously administered radioactive i@-cystine and bromobenzene. The major portion of the excreted mercapturic acid was derived from un labeled tissue sulfur compounds. On the other hand, no evidence could be found for the excretion of a labeled conjugate from 3,4-benzpyrene and L-cystine. In addition, the distribution of labeled urinary sulfur was not affected by administration of the carcinogen. These experiments have been repeated in the present study with labeled DL-methionine in place of i@-cystine with essentially the same results. This approach did not eliminate the possibility that benzpyrene might have reacted with minute amounts of unlabeled tissue sulfur compounds. Consequently, the coiitribution of labeled tissue suLfur compounds to mercapturic acid formation has been investigated with particular reference to benzpyrene conjugation. Sulfur compounds of the body of the rat were labeled with S35 by feeding radioactive DL-methio nine over a period of 15 days. 3,4-Benzpyrene, anthracene, phenanthrene, or bromobenzene was administered. The urine was collected for a period of 48 hours and fractionated. A mercapturic acid arising from the conjugation of any of these aro matic compounds with labeled tissue sulfur was accessible to measurement by the methods of the radioactive tracer technic. The conjugates cx pected from bromobenzene and anthracene were detected in the chloroform fractions. Following the administration of phenanthrene, appreciable amounts of “chloroform-soluble―sulfur were also found. There was no evidence of the formation