CHARACTERIZATION OF KININASES IN TESTICULAR CELLS

Kininases are an important part of the kallikrein-kinin system. We inv estigated the pattern of kininases in rat Sertoli cells. Sertoli cells are found in the seminiferous tubule of the testis and play a key rol e in spermatogenesis. Bradykinin was actively cleaved by cultivated Se rtoli cells at the Pro(7)-Phe(8), Phe(5)-Ser(6) and Gly(4)-Phe(5) bond s as demonstrated by high performance liquid chromatography analysis. Addition of phosphoramidon and thiorphan, which are specific inhibitor s of neutral metalloendopeptidase 3.4.24.11 (NEP), strongly inhibited the degradation of bradykinin. In contrast, the kininase type II-speci fic inhibitors captopril and enalapril were only partially effective i n preventing peptidolysis. NEP and kininase type II were shown to be l ocated on Sertoli cell membranes. The action of kininase type I leads to the formation of the metabolite bradykinin(1-8) which could be dete cted in small amounts by HPLC analysis. Cleavage of the Phe(5)-Ser(6) bond might be caused by the action of the endopeptidases 24.15 and 24. 16, which are phosphoramidon-insensitive. Our results indicate that ne utral metalloendopeptidase 24.11 is the main kininase responsible for rapid bradykinin inactivation in Sertoli cells. Further kininases with minor activities are the kininases type I and II and probably the met alloendopeptidases 24.15 and 24.16.