Effects of nitric oxide synthase inhibitors on the outcome of in vitro fertilization in the mouse

Abstract

The effect of three nitric oxide (NO) synthase inhibitors, L-NG-nitro-arginine (NO2Arg), NG-Nitro-L-arginine methyl ester (L-NAME) and aminoguanidine, on in vitro fertilization in the mouse was examined. Mouse epididymal spermatozoa were capacitated in a medium with or without NO synthase inhibitors. Oocytes were inseminated and the percentage of oocytes with two pronuclei was scored after an 8-h incubation. NO2Arg and L-NAME, but not aminoguanidine, inhibited fertilization. L-NAME inhibited fertilization in a dose-dependent manner, and its effects were stereospecific. The inhibitory effect was neutralized by L-arginine but not by D-arginine. Moreover, D-NAME did not inhibit fertilization. The results suggest that NO synthase activity (presumably of the constitutive type is necessary for spermatozoa to display their full fertilizing ability.