Glutathione and gamma-glutamyl cycle enzymes in rat testis during sexual maturation.

The main enzymes of the gamma-glutamyl cycle in the testis were studied during the onset of spermatogenesis. The activities of gamma-glutamyl transpeptidase, 5-oxoprolinase, and gamma-glutamyl cysteine synthetase, and levels of glutathione were measured in testis homogenates and Sertoli cell preparations obtained from 10-, 18-, and 26-day-old rats. A significant increase of all enzyme activities with the animal age was observed. Level of glutathione also increased in an age-dependent manner. Since the gamma-glutamyl cycle is involved in the cellular incorporation of amino acids, the present findings suggest that this uptake mechanism may be relevant during spermatogenic onset in which synthesis and secretion of specific proteins are essential for germ cell development.