Abstract
The mechanism of the myostimulating activity of rat tissue kallikrein on rat uterus was re-examined using uterus from kininogen-deficient rats and HOE 140 (D-Arg[Hyp3, Thi5, D-Tic7, Oic8]bradykinin), a specific bradykinin receptor-B2 antagonist. The uterus from kininogen-deficient rats was 50 times less sensitive to rat kallikrein than that from normal rats. HOE 140 (6 to 60 nM) inhibited the contracting effects of bradykinin and of rat kallikrein. Porcine kallikrein had no effect on rat uterus. Bradykinin and rat kallikrein induced a relaxation of rat duodenum. The duodenum from kininogen-deficient rats was 100 times less sensitive to rat kallikrein than the duodenum from normal rats. HOE 140 (0.6 to 3 nM) inhibited the relaxing effects of bradykinin and of kallikrein. Preincubation of rat kallikrein with aprotinin (Trasylol) abolished the effects of kallikrein on smooth muscles. HOE 140 inhibited the amidolytic activity of tissue kallikrein with a Ki value of 220 microM. HOE 140, at micromolar concentrations, suppressed the kininogenase activity of tissue kallikrein. Plasma of deficient rats contained 0.7% of the normal levels of kininogens. After washing the blood vessels with saline, kininogens were present in uterine homogenates but not in duodenal homogenates from both rat strains.(ABSTRACT TRUNCATED AT 250 WORDS)
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