THE INHIBITORY EFFECTS OF GOSSYPOL ON HUMAN SPERM MOTILITY CHARACTERISTICS - POSSIBLE MODES OF REVERSIBILITY OF THOSE EFFECTS

Gossypol (GOS) is a polyphenolic compound derived mainly from cottonse ed oil, which has been found to have anti-fertility effects in males. It has been reported to induce disturbances of the hypothalamicpituita ry axis, disruption of spermatogenesis in the testes, and inhibition o f postejaculatory spermatozoa motility. The inhibition of human sperm motility by GOS has been documented both in vivo and in vitro, althoug h the exact mechanism and possible reversibility of such inhibition is unknown. The objectives of the present study mere 1) to examine the i n vitro dose response of human sperm motility to GOS, and 2) to determ ine if the motility inhibition of GOS was reversible, using agents whi ch alter the second messenger cyclic adenosine monophosphate (cAMP), s uch as, 8-bromo-cAMP (8-Br-cAMP), and forskolin, and adenylate cyclase stimulator. Fresh spermatozoa were obtained from males of known ferti lity. Motile spermatozoa mere recovered via the SpermPrep(TM) (SP) met hod and used further in all experiments. Quantitative and qualitative sperm parameters were recorded at collection, post-SP filtration and p ost-treatment. Motile spermatozoa were resuspended in either media (SP ), or in increasing concentrations of GOS (10, 20, 30 and 50 mu g/ml) as gossypol acetic acid in media. To study the possible reversibility of the GOS effects, spematozoa already exposed to GOS for 2 hr (at the concentrations mentioned above) mere centrifuged and reconstituted in media containing either 10 mM 8-Br-cAMP or 100 mu M forskolin and mea surements of percent motility and grade of motility (0-4) were taken a t 0 time and at 30 min intervals for a total of 2 hr. Each experiment was replicated 8 times. The results obtained in this study showed that GOS inhibited sperm motility in a dose and time dependent manner. The motility characteristics of the 50 mu g/ml GOS group were lower than all other groups (p< 0.001) and the spermatozoa were completely immobi lized within 60 min. Cyclic AMP somewhat rescued the GOS-treated sperm , whereas exposure of GOS-treated sperm to forskolin had no such effec ts. The data generated in the present study suggest that GOS inhibits cAMP formation, which subsequently decreases sperm motility characteri stics. At low concentrations (up to 20 mu g/ml for 30 min), GOS inhibi tion is reversible and compounds that act to increase cAMP seem to be partially responsible for the reversal of GOS inhibition. However, GOS inhibitory effects at levels higher than 20 mu g/ml (exposed for 30 m in) mere impossible to reverse, which suggest that GOS at those levels could be an effective agent for vaginal contraception.