BRADYKININ RECEPTORS AND SIGNAL-TRANSDUCTION PATHWAYS IN PERITONEAL GUINEA-PIG MACROPHAGES

The presence of a bradykinin receptor on guinea pig peritoneal macrophages was evidenced by binding studies and by the effect of bradykinin on activation of the phospholipase C and the increase in intracellular calcium concentration ([Ca2+](i)). Binding studies demonstrated a specific, saturable binding for [H-3]bradykinin inhibited by the bradykinin B-2 (HOE 140) but not bradykinin B-1 (des-Arg(9)[Leu(8)]bradykinin) receptor antagonist. Scatchard analysis revealed a single class of B-2 bradykinin binding sites with a binding affinity (k(d)) of 0,8 nM and a receptor concentration (B-max) of 35 fmol/5 X 10(6) cells, representing approximately 4000 bradykinin receptors per cell. Kinetic studies confirmed the presence of this single binding site by the determination of similar binding affinity. Activation of peritoneal macrophages by bradykinin resulted in a time-and dose-dependent release of inositol phosphates determined by anion exchage chromatography and intracellular calcium analyzed using fura-2/AM. The increase in [Ca2+](i) induced by bradykinin was blocked by the specific bradykinin B-2 receptor antagonist HOE 140 but not by the bradykinin B-1 receptor antagonist des-Arg(9)[Leu(8)]-BK. These studies provide novel information regarding the nature of kinin receptors on guinea pig peritoneal macrophages and their signal transduction pathways.