The endothelin-1 binding site in rat liver tissue: Light- and electron-microscopic autoradiographic studies

Abstract

Background: Endothelin (ET) is known as a vasoconstrictive substance. The receptors for ET have been shown in various organs. However, little is known about the endothelin-1 (ET-1) binding sites in the liver. The aim of this study was to examine ET-1 binding sites in the liver. Methods: ET-1 binding sites in rat liver were studied in vivo by light- and electron-microscopic autoradiography using 125I-ET-1. Results: Light-microscopic autoradiographic observation revealed strong localization of grains in the sinusoidal lining cells of the hepatic lobule and a small number of grains in the luminal space of the portal vein and central vein. In the hepatic lobule, more grains were located in the periportal region, and the quantity tended to decrease from the midzonal to the pericentral region. Electron-microscopic autoradiographic observation revealed grains in Ito cells and in the endothelial cells of the portal vein, central vein, and hepatic sinusoids. Conclusions: These results suggest that ET-1 acts on Ito cells and on endothelial cells of the hepatic sinusoids, portal vein, and central vein and that its action is related to hemodynamics of the liver, particularly regulation of the microcirculation of the hepatic sinusoids.