ALTERATION OF MEMBRANE-PERMEABILITY TO CALCIUM-IONS DURING MATURATION OF BOVINE SPERMATOZOA

Bovine spermatozoa, maturing in the caudal epididymis, apparently have a low content of mobilizable Ca2+ (6 ± 1 nmoles Ca2+ 108 cells) in situ, but will accumulate added Ca2+ when simply diluted into isotonic media. It is suggested that the low concentrations of Ca2+ (0.5 ± 0.1 mM) and O2 present in epididymal fluids prevent the accumulatin of Ca2+ by sperm prior to ejaculation. Although the seminal plasma that surrounds ejaculated sperm contains 9 ± 1 mM Ca2+, washed ejaculated sperm also have a low Ca2+ content (7 ± 1 nmoles Ca2+ 108 cells). Moreover, in contrast to epididymal sperm, washed ejaculated sperm are incapable of accumulating Ca2+ supplied exogenously. Evidence is presented that bovine seminal fluids contain a component that is added to the surface membranes of the sperm at ejaculation which prevents or delays the active uptake of Ca2+ by these cells. © 1979.