Effect of pharmacologic interventions on aldehyde dehydrogenase in the rat testicles

The in vitro and in vivo effects of selected pharmacologic agents on cytosolic aldehyde dehydrogenase in the adult rat testicles were studied. Naltrexone, a narcotic antagonist, significantly inhibited epididymal but not testicular aldehyde dehydrogenase in vitro. Greater in vitro inhibition of aldehyde dehydrogenase in the epididymal preparation was determined in the presence of diphenhydramine, a histamine H1-receptor antagonist and by amantadine hydrochloride, an antiviral/antiparkinsonian agent. The latter drug also inhibited testicular aldehyde dehydrogenase from corresponding controls. The in vitro inhibition was noncompetitive as evaluated by reciprocal plots of the velocity of the reaction as a function of substrate concentrations. Short-term oral administration of a biologically active metabolite of flutamide, a nonsteroidal antiandrogen, significantly induced testicular aldehyde dehydrogenase without concomitant changes in epididymal aldehyde dehydrogenase from respective controls. Conversely, administration of ethinylestradiol, an estrogenic steroid, inhibited testicular but not epididymal aldehyde hydrogenase in the rat.