Changes occurring in the proteins of bovine spermatozoa during their migration from the caput to the cauda epididymidis were studied.
The percentage of total nitrogen in the dry matter was greater in the cauda than in the caput spermatozoa, but the nitrogen content/109 cells was less in the cauda spermatozoa. The amount of DNA for the same number of cells remained constant during this stage of maturation. The decrease in the nitrogen content indicated a loss of protein during maturation of bovine spermatozoa in the epididymis. Amino acid analysis of the dry matter of the sperm cells showed an increase in the percentage of arginine and cystine and a decrease in the percentage of glutamic and aspartic acids, alanine, methionine, isoleucine and leucine during passage of spermatozoa through the epididymis. Lipoprotein content decreased during the maturation of the sperm cells, and a slight increase occurred in several of the other proteins. Amino acid analysis of the extracted proteins showed differences in the percentage of several amino acids between caput and cauda spermatozoa in the F1 and F2 fractions. Gel disc electrophoresis of the various caput and cauda sperm proteins indicated a different number of bands and a different colour intensity for those fractions in which a different amino acid composition was found.
The results suggest that the lipoproteins of the cell membrane may be the site of alterations in the quantity, composition and electrophoretic behaviour of the proteins of bovine spermatozoa during their maturation.