Enzymatic digestion of bradykinin by rat Sertoli cell cultures

Sertoli cells play a key role in spermatogenesis. To study the involvement of the kallikrein-kinin system in the testis, the pattern of bradykinin-inactivating kininases in rat Sertoli cells was investigated. Exogenous bradykinin (Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9) is cleaved at Pro7-Phe8, Phe5-Ser6, and Gly4-Phe5, as demonstrated by high performance liquid chromatography analysis. Degradation of bradykinin was strongly inhibited by phosphoramidon and thiorphan, which are specific inhibitors of neutral metalloendopeptidase-24.11. The kininase type II-specific inhibitors, captopril and enalapril, were only partially effective in preventing peptidolysis. This indicates that the main kininases responsible for rapid bradykinin inactivation are neutral metalloendopeptidase and, to a lesser extent, kininase type II. Neutral metalloendopeptidase and kininase type II were shown to be located on Sertoli cell membranes. A low degree of bradykinin degradation was detected by simultaneous inhibition of neutral metalloendopeptidase-24.11 and kininase II, pointing out the involvement of further peptidases with minor activities. This remaining activity is probably not due to the action of kininase type I or cysteine proteases, as shown by specific inhibitors. The data presented indicate the occurrence of membrane-bound kininases, which are an important part of the kallikrein-kinin system, in rat Sertoli cell cultures.