PROBING FOR THE BRADYKININ B2 RECEPTOR IN RAT-KIDNEY BY ANTIPEPTIDE AND ANTI-LIGAND ANTIBODIES

The kallikrein-kinin system is involved in the inflammatory process, i n blood pressure regulation, and in renal homeostasis: The presence of kallikreins, kininogens, and kinins in renal tissues and fluids is we ll established; however, the occurrence and distribution of the bradyk inin (B2) receptor in the kidney are unknown, Using chemically cross-l inked conjugates of,bovine serum albumin and;the B2 agonist bradykinin or the potent B2 antagonist HOE140, followed by antibodies to the res pective ligand and the peroxidase-anti-peroxidase system, we were able to detect the B2 receptor. The receptor has been found in straight po rtions of the proximal tubules, in distal straight tubules, in connect ing tubules, and in collecting ducts of rat kidney. The staining patte rns produced by the ligand conjugate-anti-ligand approach are in agree ment with those obtained by conventional autoradiography using [I-125] -Tyr(0)-bradykinin. Immunocytochemical localization of B2 receptor by antipeptide antibodies to the receptor confirmed these findings and de monstrated the presence of B2 receptor in the basal infoldings and lum inal membranes of the tubule cells, and in smooth muscle cells of the cortical radial artery and of afferent arterioles. Go-localization of the B2 receptor with kallikrein and kininogens in connecting tubule ce ll and collecting duct cell layers, respectively, provides a structura l basis for the hypothesized physiological functions of the kallikrein -kinin system in the kidney,