In vivo study of LDH isoenzyme activities in heart, liver and testis cytosols of gossypol-treated rats.

LDH isoenzyme activities of heart, liver and testis homogenates were measured in rats treated for 15 or 30 days with 30 mg gossypol acetic acid/kg body weight daily, a dose which severely suppressed sperm motility. No differences in LDH activities of the examined organs were found in comparison with control animals. LDH-X, the main LDH isoenzyme in spermatozoa and testicular germ cells from primary spermatocytes onwards was also unaffected. These results contrast with in vitro experiments on human, rabbit, and boar spermatozoa, purified bovine LDH-X and rat testis homogenate which show dose-dependent inhibition of LDH-X after incubation with gossypol. Our results therefore suggest that inhibition of LDH by gossypol is not the primary cause of sperm immotility.