AMINOPEPTIDASES OF RAT TESTIS

Summary. Four aminopeptidases of rat testicular tissue were quantified during pubertal maturation, after cryptorchidism, and following cadmium chloride treatment. The assay conditions were based on differential substrate and modifier characteristics outlined previously. Aminopeptidase I with Val-β-naphthylamide (β-NA) and aminopeptidase II with Ala-β-NA and EDTA as activator showed a high activity in the prepubertal testis. A marked increase in activity after cryptorchidism suggested a Leydig cell origin for these enzymes. Aminopeptidase III was characterized as aminopeptidase B and quantified with Arg-β-NA as substrate. The activity of this enzyme closely followed the maturation of spermatogenesis during puberty and showed a rapid decrease after cryptorchidism. The differential quantification of Aminopeptidase IV was unsuccessful but there was evidence to suggest that its origin was in the seminiferous tubules. There was a suppression of the activity of all four enzymes after cadmium chloride treatment following the necrotic changes in the testis.