CHANGES IN THE NATURE OF CALCIUM-TRANSPORT SYSTEMS ON THE PORCINE SPERM PLASMA-MEMBRANE DURING EPIDIDYMAL MATURATION

Comparative studies of Ca-45(2+)-transport across the plasma membrane were performed using porcine caput, corpus and cauda epididymal sperm. The Ca2+-uptake is dependent on the presence of the substrates for respiration and is sensitive to verapamil. The Ca2+-efflux is mediated by both Na+-dependent and -independent systems. In the immature sperm in caput epididymis, Na+-independent efflux is predominant, but it is gradually replaced by Na+-dependent efflux during the epididymal transit. The net activity of Ca2+ accumulation into sperm increases with the epididymal maturation.