Effect of ornidazole on fertility of male rats: inhibition of a glycolysis-related motility pattern and zona binding required for fertilization in vitro

The effects of the male antifertility agent ornidazole on glycolysis as a p rerequisite for fertilization were investigated in rats. Antifertility dose s of ornidazole inhibited glycolysis within mature spermatozoa as determine d from the lack of glucose utilization, reduced acidosis under anaerobic co nditions and reduced glycolytic enzyme activity. As a consequence, cauda ep ididymidal spermatozoa from ornidazole-fed rats were unable to fertilize ra t oocytes in vitro, with or without cumulus cells, which was not due to tra nsfer of an inhibitor In epididymal fluid with the spermatozoa. Under IVF c onditions, binding to the zona pellucida was reduced in spermatozoa from or nidazole-fed males and the spermatozoa did not undergo a change in swimming pattern, which was observed in controls. The block to fertilization could be explained by the disruption of glycolysis-dependent events, since reduce d binding to the zona pellucida and a lack of kinematic changes were demons trated by control spermatozoa in glucose-free media in the presence of resp iratory substrates. The importance of glycolysis for binding to, and penetr ation of, the zona pellucida, and hyperactivation in rats is discussed in r elation to the glycolytic production of ATP in the principal piece in which local deprivation of energy may explain the reduced force of spermatozoa f rom ornidazole-fed males.