Comparison of kinins derived from rat stomach tissue and produced by catheptic enzyme in rat stomach.

Four uterine-contractile substances (a, b, c and d) and three uterine-contractile substances (a', c' and d') were obtained from the reaction mixture of rat plasma kininogen with the kinin-forming enzyme in rat stomach and the homogenate of the rat stomach with 0.2% acetic acid, respectively. By high performance liquid chromatography with a Zorbax ODS reversed-phase column, the retention times of materials a, c and d were found to be equal to those of materials a', c' and d', and they were not equal to those of kallidin, methionyl-lysyl-bradykinin (MLBK) and bradykinin (BK). The retention time of material b was equal to that of BK. The uterine-contractile activities of the materials a, b, c, d, a', c' and d' were all abolished by chymotrypsin, but not by trypsin treatment. These materials all relaxed the isolated rat duodenum in the presence of atropine, dibenamine, diphenhydramine and propranolol, and they produced a fall in rabbit blood pressure after administration of atropine, dibenamine and propranolol. The content ratios of a: b: c: d and a': c': d' were 4: 4: 67: 25 and 65: 19: 16, respectively, as calculated from the uterine-contractile activities of these materials.