Degradation pathway of kinins in tumor ascites and inhibition by kininase inhibitors: Analysis by HPLC

Abstract

We have recently found presence of a high concentration of a novel type of kinin, hydroxyprolyl³-bradykinin (Hyp³-BK) in human tumor ascites in addition to conventional bradykinin (BK). Because of their potential physiological activity, it is of interest to know how these bradykinins can be degraded in ascites. Degradation of two synthetic kinins, BK and Hyp³-BK, added to the ascitic fluid from patients with ovarian carcinoma and hepatoma, were analyzed by reversed phase HPLC. Both kinins were degraded into their desArg⁹-BK or-Hyp³-BK and desPhe⁸-Arg-⁹-BK or-Hyp³-BK products following incubation with the ascitic fluid. The rate of the degradation of BK and Hyp³-BK was the same. The formation of desArg⁹-BK was completely inhibited by kininase I inhibitor, while the formation of desPhe⁸-Arg⁹-BK was not completely inhibited by a kininase II inhibitor. The degradation of both kinins was inhibited completely by EDTA. The results indicate the presence of other metalloprotease(s) which cleaves kinins in the ascitic fluid, in addition to kininase I and kininase II. The carboxypeptidase A and carboxypeptidase B inhibitor, benzyl malic acid, failed to block degradation of both kinins. A rapid cleave of Phe-Arg into Phe and Arg was also found in the ascitic fluid. Thus, the major degradation products of kinins in the ascitic fluid were demonstrated to be either desArg⁹-BK or Hyp³-BK, desPhe⁸-Arg⁹-BK or-Hyp³-BK, phenylalanine and arginine. Lysyl-BK and lysylhydroxyprolyl³-BK were rapidly converted into BK and hydroxyprolyl³-BK by the ascitic fluid.