Increase of methionine aminopeptidase activity in hyperplastic Leydig cells of rat cryptorchid testis: a histochemical study.

Histochemical study on the changes of the aminopeptidase activities in rat testes after surgically-induced cryptorchidism was conducted comparing them with the histochemical changes in regenerated hepatic cells of the partially hepatectomized rat liver. Methionine-aminopeptidase in Leydig cells gradually increased after cryptorchid was induced, whereas the enzyme activity in regenerated hepatic cells decreased. These histochemical observations were coincident with the data obtained by enzyme assay. The present study has indicated that in the rat cryptorchid testis the increase of methionine-aminopeptidase activity was caused by hyperplastic Leydig cells.