Kinin formation by catheptic enzyme in rat stomach.

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Abstract
Four uterine-contractile substances (a, b, c and d) were extracted with acetic acid, n-butanol, distilled water and methanol from a reaction mixture obtained by incubating rat plasma kininogen with the kinin-forming enzyme in the rat stomach. Gradient and equilibrium chromatography on SP-Sephadex C-25 columns were carried out with the extract containing these materials (a, b, c and d). The materials could not be separated by chromatography on SP-Sephadex C-25, but were separated by high performance liquid chromatography (HPLC) with a Zorbax ODS reversed-phase column. All the materials (a, b, c and d) contracted rat uterus and relaxed rat duodenum. The uterine-contractile activity of the materials was abolished by chymotrypsin, but not by trypsin treatment. The retention times of materials a, c and d on HPLC wre different from that of kallidin, MLBK, bradykinin (BK) and neurotensin; but the retention time of material b was equal to that of BK. The content ratio of a:b:c:d was 4:4:67:25, calculated from the uterine-contractile activity of these materials. The apparent MW of the major material c, estimated by gel chromatography, was 1650. Material c contracted rat uterus (1.2 .times. 10-10 g/ml), relaxed rat duodenum (2 .times. 10-10 g/ml), and produced a fall in rabbit blood pressure (4.4 .times. 10-8 g/kg). Material c was classified as a biologically BK-like peptide which is distinct from kallidin, MLBK, BK and neurotensin.

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