Bradykinin receptors in rat uterine smooth muscle: Studies using radiolabeled ligand binding.

Abstract

Direct binding of 1251-Tyr8-bradykinin to a microsomal fraction prepared from rat uterine smooth muscle, showed an apparent dissociation constant (KD) at 29°C of 5.0 x 10-10 M calculated from kinetic studies and 6.6 X 10-10 M from Scatchard plot analysis. The binding of 1251-Tyr8-bradykinin was reversible and saturable , and demonstrated high specificity for Tyr8-bradykinin, bradykinin and Lys-bradykinin, but was not displaced by unrelated peptides angiotensin I, angiotensin II, Arg8-vasopressin and oxytocin. The binding sites were copurified by differential centrifugation and on a discontinuous sucrose density gradient with 5'-nucleotidase activity, a plasma membrane marker enzyme. Prolonged intravenous infusion of bradykinin (5 nmol/h for 2 days) induced a 20% decrease in the number of bradykinin binding sites without a change in the equilibrium dissociation constant. The present results demonstrate that receptors mediating the effect of bradykinin on rat uterine smooth muscle are situated on plasma membranes and the regulation of the receptors is in part under the control of endogenous bradykinin levels. receptor regulation ; myometrial membranes ; 125I-Tyr8-bradykinin ; bradykinin infusion Bradykinin and other kinins modify cardiovascular hemodynamics by influencing vascular smooth muscle tone. The mechanism of action of bradykinin on vascular smooth muscle remains uncertain as characterisation of the bradykinin-receptor interaction has not been fully documented (Odya and Goodfriend 1979). Receptor binding is the first event in the series of molecular processes leading to hormonal effects in the target tissue and is also important both

Receptor-binding characteristics and contractile responsiveness of the myometrium following prolonged infusion of bradykinin and oxytocin in rats

“…The binding of bradykinin to rat uterine smooth muscle is not displaced by angiotensin I, angiotensin II, arginine vasopressin or oxytocin (Yasujima et al 1984) and the contractile effect of oxytocin and bradykinin on the myometrium therefore does not appear to be mediated through the same receptor. On the other hand, the action of both bradykinin and oxytocin on the whole rat uterus involves release of prostaglandins (Whalley, 1978).…”

“…Oxytocin and bradykinin bind to separate classes of receptors (Melin et al 1981) and oxytocin cannot displace [3H]bradykinin from myometrial membrane preparations (Yasujima et al 1984) or vice versa (authors' unpublished results). It is therefore possible that long-term occupancy of the oxytocin receptor affects a common intracellular pathway for peptide receptor production, transport or membrane incorporation.…”

“…Most investigators have described the pres¬ ence of only one class of oxytocin receptor in the myometrium (Soloff & Swartz, 1974;Soloff, Schroeder, Chakraborty & Pearlmutter, 1977;Alexandrova & Soloff, 1980;Jard, 1980), although Pliska, Heiniger, Muller-Lhotsky et al (1986) reported the existence of at least three populations of receptors binding oxytocin to cultured ovine myometrial cells. Yasujima, Matthews & Johnston (1984) showed that i.v. infusions of bradykinin in rats resulted in a 20% reduction in the number of uterine bradykinin receptors.…”

Hypotensive effect of captopril and decreased rat uterine bradykinin receptors.

“…Bradykinin receptor binding studies were performed with '25I-Tyr8-bradykinin with 100-300 Ci/mmol of specific activity. The preparation for subcellular fraction enriched in plasma membrane and the determination of specific 125I-Tyr8-bradykinin binding, were done as detailed elsewhere (Yasujima et al 1984). The apparent affinity and the number of binding sites were determined from Scatchard plot analysis (Scatchard 1949) of concentration dependent binding at initial concentrations from 2 X 10-10 M to 1.2 X 10-9 M of 125I-Tyr8-bradykinin.…”

“…Recent study from this laboratory has demonstrated that captopril stimulates urinary excretion of kinin, an indicator of renal kinin synthesis or its degradation, in anaesthetized dogs, contributing to subsequent changes in renal hemodynamics (Clappison et al 1980). Furthermore we characterized bradykinin receptors in rat uterine smooth muscle, frequently used model of vascular smooth muscle and showed that its membrane receptors was down-regulated by endogenous bradykinin (Yasujima et al 1984).…”