Comparative metabolism of the cysteine and homocysteine conjugates of propachlor by in situ perfused kidneys of rats

Abstract

1. ¹⁴C-Cysteinyl- and homocysteinylpropachlor were metabolized to their respective mercapturic acids by rat kidneys in situ. First-pass elimination of ¹⁴C in urine was 47·5% for the cysteine conjugate and 36% for the homocysteine conjugate.

2. About half of the perfused ¹⁴C-labelled material isolated from urine from kidneys perfused with homocysteinylpropachlor was unchanged homocysteinylpropachlor and about half was the corresponding mercapturic acid. However, only the corresponding mercapturic acid and the S-oxide of this mercapturic acid (31·4% and 1·7% of the dose) were found in urine from kidneys perfused with cysteinylpropachlor, indicating that rat kidneys more efficiently acetylated the natural substrate, the cysteine conjugate.