AJP - Renal Physiology, Vol 267, Issue 5 845-F852, Copyright © 1994 by American Physiological Society
Cellular distribution of 125I-endothelin-1 binding in rat kidney following in vivo labeling
R. Dean, J. Zhuo, D. Alcorn, D. Casley and F. A. Mendelsohn
Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg.
Endothelin-1 (ET-1) receptors have previously been demonstrated in the rat
kidney by in vitro autoradiography and in cultured renal cell lines by
radioreceptor assay, but the precise cellular localization of these
receptors under in vivo conditions remains to be determined. We performed
electron microscopic autoradiography on rat kidney following intravenous
administration of 125I-labeled ET-1. In vivo autoradiographs revealed
binding patterns identical to those previously demonstrated following in
vitro labeling. Light microscopic autoradiography showed that silver grains
occurred exclusively overlaying glomeruli and peritubular capillaries in
the cortex, inner stripe of the outer medulla, and the inner medulla. At
the electron microscopic level, ET-1 binding was specifically localized to
the fenestrated endothelium of glomerular and peritubular capillaries, and
to a lesser extent to the vasa recta. No significant grains were seen on
mesangial or visceral epithelial cells; nor were any seen on the cells of
proximal tubule, the thick and thin limbs of the loop of Henle, the
medullary collecting ducts, and renal interstitial cells. These results
indicate that the endothelial cells of glomerular and peritubular
capillaries are the primary target for the circulating ET-1 in the rat
kidney and suggest an autocrine and/or paracrine function of locally
synthesized ET-1 in vivo in both physiological and pathophysiological
states.
