Demonstration of Specific Binding of Cocaine to Human Spermatozoa

Exposure of males to cocaine has been linked to abnormal development of their offspring. To investigate the possible role of sperm, this study examined the interaction of cocaine with human spermatozoa. Washed sperm were incubated with tritiated cocaine (6.7 nmol/L) with or without unlabeled cocaine (670 μmol/L), and the samples were filtered and the remaining radioactivity quantitated. The specific binding was optimal at 20 minutes and 23°C. Competition studies with tritiated cocaine (3.4 to 66.6 nmol/L) indicated the presence of approximately 3.6× 10³ binding sites per cell, with a high affinity receptor dissociation constant (K_d = 12.6 nmol/L). Cocaine concentrations as high as 670 μmol/L had no detectable effect on either the motility or viability of the cells. These results support the hypothesis that the sperm may act as a vector to transport cocaine into an ovum. This novel mechanism could be involved in the abnormal development of offspring of cocaine-exposed males.