IN-VITRO TESTICULAR BIOACTIVATION OF ACRYLONITRILE

The present work examines the mechanism of testicular toxicity of acry lonitrile. In testicular centrifugal fractions from Sprague Dawley rat s, the metabolism of VCN to cyanide (CN-) was highest in the microsoma l fraction and required NADPH for maximum activity. This biotransforma tion of VCN to CN- was characterized with respect to time (30 min), mi crosomal protein concentration (1.5 mg ml(-1)), pH (7.5) and temperatu re (37 degrees C). The V-max of the reaction was 65.1 pmol CN- mg prot ein(-1) min(-1) and K-m was 88.6 mu mol VCN. Flushing the microsomes w ith carbon monoxide (CO)(4:1, CO/O-2 v/v), addition of benzimidazole ( 1 mM) or addition of SKF 525-A (5x10(-4) M) to incubation mixtures sig nificantly inhibited VCN metabolism by 49%, 54% and 37.4% respectively . Activation of VCN to CN- was markedly increased in microsomes obtain ed from phenobarbital (PB)-treated rats (128.2%). Addition of glutathi one (GSH), L-cysteine, D-penicillamine or 2-mercaptoethanol significan tly enhanced the release of CN- from VCN 126%, 247%, 202% and 129% of the control value respectively. These findings indicate that VCN is me tabolized in the testis via cytochrome P-450 dependent mixed function oxidase system. (C) 1997 The Italian Pharmacological Society.