Interaction of 14 C-gossypol with human sperm

Gossypol, a bis-sesquiterpene, suppresses spermatogenesis and inhibits sperm motility. The direct interaction of gossypol with human sperm was investigated. Conditions influencing the interaction of 14c-gossypol (radiolabeled on the aldehyde group with specific activity of 3.33 x 10 5 dpm per micromole) with human sperm reached saturation rapidly. Within 1 minute of exposure of motile sperm to 10 uM radiolabeled gossypol at 37 degrees Centigrade, the cincorporation of 14c-gossyol was 17 at 35% at densities of 2.5 x 106 and 8.6 x 106 per ml, respectively. Immobile sperm prepared by heating at 60 degrees Centigrade for 10 minutes incorporated the same amount of 14c-gossypol as motile sperm. Uptake of 14c-gossypol was slightly greater at 37 degrees Centigrade than at 4 degrees Centigrade, and under acidic conditions. To identify the sperm membrane components interacting with gossypol radiolabeled sperm were treated with the following 3 solutions to solubilize the membrane proteins: 0.1% Triton X-100; 1 M urea, 5 mM EDTA in 19mM Tris-HC1, pH 8.3; and 20% sodium doydecyl sulfate (SDS), 0.1M 20mercaptoethanol. The amount of radiolabeled proteins solubilized with respective media were 11, 23, and 67% with specific activities of 1.8 x 103, 2.1 x 105, and 0.3 x 103 cpm per mg protein. The radiolabeled substances solubilized with SDS, mercaptoethanol reagent were separated by gel filtration on Sephadex G-100 column. 3 peaks of radioactivities corresponding to molecular weights of approximately 100, 35, and 25 KD were eluted. The highest radioactivity was found with the 100 KD fraction. The interaction of gossypol with sperm membrane proteins is an early event, followed by inhibition of sperm motility.