Induction of reversible infertility in male rats by oral ornidazole and its effects on sperm motility and epididymal secretions

Abstract

Omidazole (400 mg kg-1 day -1) given by oral gavage rendered male rats infertile by 6.6 ± 0.7 days (mean ± SEM, n = 9, range 3-10) after beginning the treatment and fertility returned within 5-10 days after treatment with omidazole for 6-7 days. At 200 mg omidazole kg-1 day -1, fertility was reduced but total infertility was not achieved. No differences were found in the percentage motility of spermatozoa recovered from any region of the epididymides of omidazole-treated rats compared with controls. However, computer aided sperm analysis revealed significantly lower straight-line and average path velocities in omidazole-treated animals (400 mg kg-1 day -1) for spermatozoa from the distal regions of the tract than for controls. Curvilinear velocity was significantly lower than that of controls in the distal corpus and cauda regions. The motility characteristics of spermatozoa from animals receiving 200 mg omidazole kg-1 day were lower than, but not significantly different from, motility in controls. There were no differences between the total protein, L-carnitine, glycerophosphocholine or total α-glucosidase content in epididymal homogenates from fertile control and infertile omidazole-treated animals. Spermatozoa released from the cauda epididymidis of untreated rats into omidazole solutions displayed no changes in the percentage motility up to 20 mmol l-1 and were only depressed at 50 mmol l-1. All velocities revealed a biphasic response with an initial increase in motility and then inhibition at higher concentrations, but a significant difference from velocities in the absence of ornidazole was evident only for straight line velocity (VSL) at 50 mmol l-1 The rapidity of action in inducing infertility is compatible with post-testicular action and an action on the epididymis is suggested by the decline in motility parameters of luminal spermatozoa. The lack of effect on epididymal secretions in vivo and on sperm motility in vitro, except at very high doses, suggests that there may be a direct action of an omidazole metabolite on epididymal spermatozoa.