Gossypol-induced inhibition of glucose uptake in human ejaculated spermatozoa may be mediated by lipid peroxidation

Abstract

Gossypol, a plant-derived polyphenolic compound known to exert contraceptive actions in men, inhibits 14C-glucose uptake in vitro in human ejaculated spermatozoa. Spermatozoal glucose uptake was found to increase monotonically up to 40 min, and then decreased by 60 min, possibly because of the saturation of the transport loci in the membrane. Gossypol at the concentrations of 5 and 10 μm caused a reduction of both the linear portion of the uptake and the fall afterwards. Gossypol similarly affects both the Na-dependent and -independent glucose uptake. The kinetic parameters of glucose uptake indicate that gossypol might be interfering with the transport/carrier protein as reduction in maximum uptake velocity (Vmax) was observed without any change in the affinity constant (Km). Similarly, gossypol also produced an increase in spermatozoal lipid peroxidation as evidenced by a steep rise in thiobarbituric acid reaction products in the human sperm cells. A significant decrease in total phospholipid level and the individual classes was noted after gossypol addition. Gossypol-induced inhibition of glucose uptake may be related to the generation of lipid peroxides and consequent membrane damage.