Lectin binding sites on the plasma membrane of epididymal and ejaculated chimpanzee sperm

Abstract

Lectins have been used to analyze variations in the distribution and density of exposed saccharides of the sperm plasma membrane during physiologic maturation and after ejaculation. Studies have been conducted in a number of nonprimate species but have been conducted to only a limited extent in nonhuman primates. In this study, pure suspensions of chimpanzee sperm from the caput and cauda epididymis and from the ejaculate were labeled with lectins conjugated to fluorescein isothiocyanate in order to visualize changes in the distribution of exposed membrane glycocomponents. The lectins used were Con A, DBA, RCA-I, and WGA. Con A binding showed minimal change during epididymal transit, with an increased binding to the flagellum after ejaculation. DBA binding was relatively constant in all specimens. RCA-I showed distinct changes in binding pattern between epididymal and ejaculated sperm. On ejaculated sperm strong fluorescence was limited to the posterior head and to the midpiece. WGA binding increased during epididymal passage and decreased after ejaculation. There appears to be a wide variety of saccharide groups available for lectin binding on the surface of epididymal and ejaculated chimpanzee sperm. The general similarity in binding patterns of caput and cauda epididymal chimpanzee sperm exposed to Con A and DBA might reflect the fact that sperm morphology does not change during epididymal transit in this species, thus implying a more stable membrane structure than is present in other primates so far studied.