Gamma glutamyl transpeptidase in the vasculature of the rat testis.

Activity of gamma glutamyl transpeptidase (GGT) in the testes of mature and prepuberal rats was investigated histochemically and biochemically. Histochemically, the enzyme activity was localized predominantly in the arterial and arteriolar endothelium and was absent from the capillaries and the seminiferous tubules. The activity in the arterial endothelium extended to the testicular artery on the surface of the testis and in the spermatic cord, but the veins in both the pampiniform plexus and on the testicular surface were negative. The endothelium of the testicular artery was already faintly positive at birth, and the activity increased during the second and third postnatal week during the branching and remodeling of the intratesticular arteries and arterioles. Activity of GGT was estimated quantitatively after dissection of the testis into tubular and interstitial tissue. The enzyme activity was very low in the tubules. It was fivefold stronger in the interstitium, and this activity was further enhanced by pretreatment of the dissected tissue with collagenase to remove the Leydig cells.