Characterization and localization of alkaline phosphatase activity in rat testes

Alkaline phosphatase activity in extracts of testes of sexually immature (13 days old) and sexually mature rats has been characterized by its heat sensitivity, the extent of inhibition by homoarginine and phenylalanine, and by polyacrylamide gel electrophoresis. The testicular enzyme appears to be a liver-bone-kidney-type alkaline phosphatase. There are no significant differences in the properties of the enzyme from animals of these two ages. Spermatocytes and early spermatids contain very little alkaline phosphatase activity; the specific activity of a nonflagellate germinal cell suspension is only 1/20th that of the whole testis. Since the constant level of activity in immature and mature animals is not consistent with the enzyme activity being present only in late spermatids, we conclude that the majority of the testicular enzyme is present in nongerminal cells. The presence of alkaline phosphatase in plasma membrane purified from testes of adult rats was demonstrated.