Evidence for existence of two distinct bradykinin receptors on rat mesangial cells

Abstract

We investigated the possible presence of bradykinin (BK) B1 receptor on rat mesangial cells (MC) by binding studies and by the effect of the B1 agonist des-Arg9-BK on intracellular calcium concentration ([Ca2+]i) and DNA synthesis in comparison with the effects of BK. Binding studies demonstrated specific, saturable binding for des-Arg9-[3H]BK inhibited by B1 but not by B2 antagonists. Scatchard analysis revealed a single class of B1 binding site with a maximum density of 15 fmol/mg protein and an affinity of 8.7 +/- 2.4 nM. Saturation and competition studies of 125I-[Tyr0]BK demonstrated the presence of two classes of B2 binding sites [dissociation constant (Kd) = 0.1 and 4 nM, respectively]. On fura-2-loaded adherent MC, both des-Arg9-BK and BK induced a biphasic increase (a transient enhancement followed by a sustained phase) in [Ca2+]i, both in primary culture and in cloned MC. Both the transient and sustained phases of [Ca2+]i induced by des-Arg9-BK were dose dependent, whereas BK induced a transient dose-dependent rise in [Ca2+]i, but the sustained phase remained constant. The increases in [Ca2+]i induced by des-Arg9-BK and BK were specifically abolished by B1 and B2 receptor antagonists, respectively, and showed homologous but not heterologous desensitization. Des-Arg9-BK and BK induced a significant proliferation (tested by cell counting and [3H]thymidine incorporation) of quiescent MC. Furthermore, the effects of des-Arg9-BK and BK were additive on Ca2+ mobilization but not on mitogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Des‐Arg9‐bradykinin‐induced increases in intracellular calcium ion concentration in single bovine tracheal smooth muscle cells

“…These values are similar to that obtained from calcium studies of the B1 receptor in rat mesangial cells (560 nM; Bascands et al, 1993) and are in the same concentration-range as those observed in the 'classic' B1 receptor system, contractile responses of the rabbit aorta, where the EC5o was found to be 50 nM (Regoli et al, 1981).…”

Bradykinin reduces growth factor-induced glomerular ERK1/2 phosphorylation

“…Glomeruli were isolated as routinely performed in the laboratory by graded sieving (6). Briefly, rats were anesthetized intraperitoneally with 65 mg/kg pentobarbital sodium (Sanofi, Montpellier, France) and killed by exsanguination, and the kidneys were quickly removed.…”

“…Whereas the initial studies conducted only with quiescent cells demonstrated mainly mitogenic effects (6,20), more recent studies by several groups report inhibitions of both cell proliferation and ERK1/2 phosphorylation by BK. Dixon and Dennis (15) evidenced an inhibition of mitogenesis by BK in arterial smooth muscle cells stimulated with PDGF-AB.…”

“…With respect to the kinin receptors, bradykinin (BK), the agonist of the kinin B 2 receptor (B 2 R), has been shown to induce proliferation in glomerular mesangial cells (6,20) and fibrosis in vascular smooth muscle cells (18). The profibrogenic effects of BK are associated with the phosphorylation of ERK1/2, which is a prerequisite for the activation of this MAPK (18).…”

Effect of bradykinin on renal mesangial cell proliferation and extracellular matrix secretion

“…The kidney contains various components of KKS, and bradykinin (BK), the most important bioactive peptide of KKS, is the final effector exerting the effects described above. The presence of BK receptors at the surface of mesangial cells has been confirmed, and the B2 receptor of BK shows particularly high expression (Bascands et al, 1993). Glomerulosclerosis is a common developmental process of chronic kidney disease, which mainly acts to increase MCP and ECM secretion.…”