The Net Surface Charge of Mammalian Spermatozoa as Determined by Isoelectric Focusing. Changes Following Sperm Maturation, Ejaculation, Incubation in the Female Tract, and after Enzyme Treatment

The mean net surface charge of living mammalian spermatozoa from various regions of the male reproductive tract has been investigated by whole cell isoelectric focusing techniques. In all cases, spermatozoa released from the caput epididymidis had a significantly higher mean isoelectric point than those from the cauda region. The net charge of spermatozoa from the rat and hamster was further modified by seminal vesicular fluid but not by prostatic secretion. Whereas the isoelectric point of caudal spermatozoa from rodents increased significantly after exposure to neuraminidase or trypsin, that of spermatozoa from the caput region was altered to a lesser extent. By contrast, neuraminidase failed to influence the surface charge of ejaculated human and rabbit spermatozoa, as did the incubation of spermatozoa in the female tract or with capacitating media. Finally, a preliminary study showed that spermatozoa from some apparently infertile men have an isoelectric point consistently higher than those from fertile men.