Male reproductive tissues express cytochrome P450 isoforms involved in the in situ metabolism of the pesticide methyl parathion in the mouse.

1. This study aimed to evaluate the bioactivation of methyl-parathion (Me-Pa) and the expression and activity of mouse cytochrome P450 (Cyp) isoforms involved, in the cauda epididymis-vas deferens (CE-VD) and testis, and in the liver for comparison.2. Microsomes were obtained from adult mice treated and non-treated with phenobarbital (PB), and the bioactivation of Me-Pa was indirectly evaluated by in vitro acetylcholinesterase inhibition. The protein content was evaluated by immunoblotting, and the enzymatic activities by resorufin ether-O-dealkylation and 16α- and 6β-testosterone hydroxylation. Me-Pa bioactivation was observed in the testis at a lower rate than in the liver and was detected in the CE-VD only after PB induction.3. The protein content and enzymatic activities associated with the Cyps evaluated were observed in all tissues in different proportions, depending on the enzyme. In all cases, protein content and enzymatic activities in the liver were higher than in reproductive tissues, except for Cyp1a2, for which constitutive expression was not observed in the CE-VD, but its associated enzymatic activity was higher compared to the testis and liver.4. These findings suggest that mouse reproductive tissues are metabolically active in biotransforming xenobiotics, such as Me-Pa, contributing to its toxicity.