Participation of vitamin A in the maturation of rabbit spermatozoa.

Vitamin A concentration was fluorometrically measured in epididymal and ejaculated rabbit spermatozoa and in some of the sperm cells subcellular components. The concentration of vitamin A in the epididymal cells was about one-half that observed in the ejaculated spermatozoa (2.68 as against 1.05 mug/10(8) cells) and seemed to be the same in the sperms obtained from both the head and the tail of the epididymus. The concentration of vitamin A was also found to be significantly higher in the seminal plasma than in the epididymal secretion (0.06 as against 0.039 mug/mg protein respectively). Practically all the vitamin A was found in the fractions obtained by treatment with hypotonic MgCl2 (acrosomal region) and/or with hyamine and dithiothreitol (plasma membrane). It was concluded that the sudden increase in the sperm concentration of vitamin A that occurs upon ejaculation may be required for the stabilization of the acrosomal and plasma membranes.