High resolution localization of endothelin receptors in rat renal medulla

Abstract

The cellular localization of endothelin receptors in the inner medulla of the rat kidney was investigated by using high resolution light and electron microscopic autoradiography, with the microwave irradiation fixation methods. Kidney slices were incubated with 125I-endothelin-1 alone or with selective ligands for the endothelin ETB and/or ETA receptors for light microscopic autoradiography. At the microscopic level, 125I-endothelin-1 was found to bind specifically to the glomeruli, arterioles and peritubular spaces in the cortex and vasa recta and surrounding tissues in the inner medulla. These bindings were also observed when the tissue slices were incubated in the presence of IRL1620 (ETB receptor agonist) or 97-139 (ETA receptor antagonist). Electron microscopic autoradiography using 125I-endothelin-1 in the inner medulla revealed silver grains over endothelial cells of the vasa recta and interstitial and collecting duct cells. No grains were detected over inner lining cells of the thin limbs of Henle's loop. These interstitial cells contained abundant microorganelles and lipid droplets, and had extensive cytoplasmic processes that closely related to the basement membranes of the vasa recta and loop of Henle. These findings demonstrate that type 1 interstitial cells are also primary sites for endothelin receptors as well as endothelial cells of the vasa recta and collecting duct cells in the inner medulla.

Endothelin A receptor-like immunoreactivity on the basal infoldings of rat renal tubules and collecting ducts

“…These membranes are known to contain Na + , K + -ATPase. In agreement with our data, ET binding sites have also been demonstrated on basal infoldings of these cells by a radiobinding study (Yukimura et al, 1996). Thus, the ETA receptor may be involved in the ET-mediating reduction of Na + , K + -ATPase activity.…”

Role of collecting duct endothelin in control of renal function and blood pressure

“…Numerous studies involving multiple species and techniques consistently demonstrate that the CD is the major renal site of ET receptor expression (16,101,103,113). As for ET-1 production, the highest binding of ET-1 is in IMCD, followed by OMCD and CCD (88).…”

Distribution of Endothelin Receptor Subtypes ETA and ETB in the Rat Kidney

“…Concurringly, these studies identified the glomeruli, longitudinal I-ET-1 binding, Interglomerular regions showed only sparse labeling, and the outer stripe of the outer medulla was completely negative (Davenport et al 1989;Kohzuki et al 1989). However, data are inconsistent concerning the determination of cellular binding sites by high-resolution light and electron microscopy (Furuya et al 1992;Dean et al 1994Dean et al ,1996Yukimura et al 1996). Furthermore, the design of these autoradiographic studies did not allow discrimination between receptor subtypes.…”

“…Few autoradiographic studies have addressed this issue by use of unlabeled ET-receptor-subtype-specific ligands. Using 125 I-ET-1 binding in the presence of excess of unlabeled ET A or ET B receptor ligands, Yukimura et al (1996), as well as Dean et al (1996), reported that the ET B receptor agonist sarafotoxin S6c abolishes 125 I-ET-1 binding almost completely with exception of binding to the inner medulla, which also could not be abolished by a combination of ET A and ET B receptor antagonists.…”