Effect of optical isomers of gossypol on mammalian spermatozoa: an in vitro study

Human, bull and monkey spermatozoa were treated with different optical isomers of gossypol in vitro. The spermatozoa (concentration 50 x 10(8)) were incubated with gossypol for 15, 30, 45 and 60 min. at 37 degrees C. The concentration of gossypol employed in the experiment was from 5-50 micrograms/ml. A marked inhibition in sperm motility was observed following gossypol treatment; levorotatory gossypol had more pronounced effect on sperm motility in comparison to dextrorotatory and racemic gossypol. Scanning electron microscope study revealed degenerative changes in the sperm head surface. Dextrorotatory gossypol, hitherto known to be non-effective in suppressing the fertility in vivo was found to be equally effective in inhibiting the motility and LDH-X activity of the spermatozoa. Both racemic and dextrorotatory gossypol inhibited fructolysis in bull spermatozoa. Our data suggest that whatever the mechanism of action of enantiomers of gossypol on sperm motility, fructolysis and LDH-X may be, it is evidently clear that dextrorotatory gossypol is equally active in inhibiting the sperm motility and enzyme active in vitro. The action of optical isomers of gossypol on spermatozoa in vitro, appears to be unrelated to the mechanism of orally administered gossypol.