Distribution of endothelin receptor subtypes ETA and ETB in the rat kidney

The endothelin (ET) receptor system is markedly involved in the regulation of renal function under both physiological and pathophysiological conditions. The present study determined the detailed cellular localization of both ET receptor subtypes, ETA and ETB, in the vascular and tubular system of the rat kidney by immunofluorescence microscopy. In the vascular system we observed both ETA and ETB receptors in the media of interlobular arteries and afferent. and efferent arterioles. In interlobar and arcuate arteries, only ETA receptors were present on vascular smooth muscle cells. ETB receptor immunoreactivity was sparse on endothelial cells of renal arteries, whereas there was strong labeling of peritubular and glomerular capillaries as well as vasa recta endothelium. ETA receptors were evident on glomerular mesangial cells and pericytes of descending vasa recta bundles. In the renal tubular system, ETB receptors were located in epithelial cells of proximal tubules and inner medullary collecting ducts, whereas ETA receptors were found in distal tubules and cortical collecting ducts. Distribution of ETA and ETB receptors in the vascular and tubular system of the rat kidney reported in the present study supports the concept that both ET receptor subtypes cooperate in mediating renal cortical vasoconstriction but exert differential and partially antagonistic effects on renal medullary function.