Identification and characterization of leukotriene C4 receptors in isolated rat renal glomeruli

The immediate reduction of renal blood flow and glomerular filtration rate in response to intravenous infusion of leukotriene C4 in the rat prompted an analysis of isolated rat renal glomeruli for the presence of specific receptors for leukotriene C4. Specific binding of [3H]leukotriene C4 to glomeruli increased in a time-dependent manner, reached equilibrium after 60 minutes of incubation at 4 degrees C, and was 80% reversible upon addition of excess unlabeled leukotriene C4 at equilibrium. Specific binding of [3H]leukotriene C4 to glomeruli increased in a dose-dependent manner, approaching saturation at concentrations of 40-60 nM. Inhibition of binding of [3H]leukotriene C4 with increasing concentrations of unlabeled leukotriene C4 was dose dependent. The equilibrium dissociation constant for [3H]leukotriene C4 binding to glomeruli, calculated from saturation and competitive binding-inhibition studies, was 25 +/- 7 nM and 35 +/- 16 nM (mean +/- SEM), respectively, and glomerular leukotriene C4 receptor density was 8.5 +/- 1.5 and 9.0 +/- 3.0 pmol/mg protein, respectively. The other natural vasoactive sulfidopeptide leukotrienes, leukotriene D4 and leukotriene E4, the chemotactic agent, leukotriene B4, and the sulfidopeptide leukotriene antagonist, FPL 55712, competed for the receptor at concentrations 2-3 orders of magnitude higher than the homoligand, leukotriene C4. The binding and specificity characteristics of the glomerular leukotriene C4 receptor are similar to those previously reported for the DDT1 nonvascular smooth muscle cell line derived from hamster vas deferens, for guinea pig ileum smooth muscle, and for a subcellular fraction of rat lung homogenate, and represent the first characterization of such a receptor in a vascular tissue.