Isotope dilution assay for urinary methanesulfinic and methanesulfonic acids: application to detection of methylthio turnover.

Methanesulfinic and methanesulfonic acids were shown to be present in urine from rats fed laboratory rat diet. The daily excretions of each acid were equivalent at 0.47 mumol day-1. The excretion of methanesulfinic acid increased about ninefold and that of methanesulfonic doubled when rats were dosed with 17 mumol of pentachlorothioanisole. The excretion of methanesulfinic acid above control levels in urine may be a method for detecting methylthio displacements that occur during the intermediary metabolism of xenobiotics.