title: Cytochemical analysis of the anionic sites on the membrane of the stallion spermatozoa during the epididymal transit.
abstract: The structure, relative density, and distribution of anionic sites on the surface of epididymal and ejaculated spermatozoa were studied using polycationic ferritin (CF), colloidal iron hydroxide (CIH), various enzymatic treatments, methylation, and de-acetylation. Macro-molecules containing sugar residues, probably sialic acid, are part of the sperm membrane and show a characteristic distribution and density that is dependent of the sperm region and of its origin. Unlike the spermatozoa of other eutheria examined, the exposure of the stallion spermatozoa to neuraminidase treatment did not produce significant changes in the density of the negative charge of the sperm surface. The ability of purified neuraminidase to act only after saponification suggests that sialic acid may be present in the acetylated form. When CIH was used it is seen that the density of the negative charge is rather uniform within a particular segment of the spermatozoa and abruptly changes at the junction of morphologically distinct segments (Between the acrosomal and post acrosomal region of the sperm head and between the post acrosomal region and middle piece of the flagellum). The acrosome presented more negative groups dissociated at pH 1.8 than the postacrosomal region. A greater concentration of anionic sites over the flagellum was also observed when CIH and CF were used. This asymmetry probably represents different domains that may be related to specific functions. The cytochemical observations and the cellular electrophoretic mobility measurements did not show striking differences on the negative charge of sperm obtained from different regions of epididymis and ejaculates in contrast to previous results in other species. The spermatozoa collected from caput epididymidis bind CIH but not all population present equal response. In corpus and cauda region of epididymis the population displaying the capacity to bind CIH or CF significantly over the head and tail surface was the majority. This study corroborates that the distribution and density of terminal oligosaccharide residues on the sperm plasma membrane has species specific characteristics. The surface charge of the spermatozoa obtained either during the breeding or nonbreeding season, determined by measurements of cellular electrophoretic mobility and by the binding pattern of CIH and CF, does not show significant differences.
mesh_terms: D000818:Animals; D000838:Anions; D002462:Cell Membrane / Q000032:analysis*; D004822:Epididymis; D006736:Horses; D008297:Male; D013079:Sperm Maturation; D013081:Sperm Motility; D013094:Spermatozoa / Q000032:analysis / Q000166:cytology*
chemical_list: D000838:Anions