[Evidence for a glomerular receptor for bradykinin in rats. Effect of sodium intake on density and affinity of the receptor].

Bradykinin (BK) have been involved in a lot of pharmacological and biological effects including natriuresis, vasodilatation, inflammation and pain mediation. All these potent effects of BK are presumably mediated via one or more specific receptors which have been classified in two types named B1 and B2 receptors. In the kidney, specific binding have been reported successively in cortical epithelial membranes, in renomedullary interstitial cells and in cortical collecting tubules. Furthermore, since a large number of vasoactive compounds have been shown to regulate renal glomerular hemodynamics, we examined the binding of BK in rat glomerular membranes and the effect of variable salt diet on the density (Bmax) and the dissociation constant (KD) of this binding. Incubation of a radiolabeled bradykinin analog, [125I]-Tyr8-BK with a crude membrane preparation obtained from isolated rat glomeruli revealed a time dependent binding. The binding was saturable, reversible and was a linear function of protein membrane concentration. The radiolabeled Tyr8-BK bound to a single class of binding sites with an equilibrium dissociation constant (KD) of 2.75 +/- 0.7 nM and a density (Bmax) of 32.1 +/- 5.2 fmol/mg protein. [125I]-Tyr8-BK binding was reversed by bradykinin (Ki = 0.4 10(-9) M) and by other kinin analogs. However, Des-Arg9-BK had no effect on binding of the radiolabelled BK. These results are consistent with the presence of a B2-kinin like receptor in rat glomeruli. Low salt diet (during one month) and water deprivation (during 4 days) induced a decrease in the density of glomerular BK like receptors respectively (Bmax = 12.45 +/- 1.3 and 13.25 +/- 1.17 fmol/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)