Polarized distribution of the renal natriuretic peptide receptors in normal physiology and ischemia. Ritter, Detlef, Alan D. Dean, Zhong-Hong Guan, and James E. Greenwald. Departments of Medicine, Molecular Biology and Pharmacology, and Pathology, Washington University School of Medicine, St. Louis, Missouri 63110
APStracts 2:0107F, 1995.
The polarized expression of guanylyl cyclase coupled natriuretic peptide receptors, type A (GC-A) and type B (GC-B), was measured in inner medullary collecting ducts of normal and ischemic rat kidneys, as well as in cultured inner medullary collecting duct cells. Exposure of normal rat kidney medulla to an anti GC-A antibody demonstrated a propensity of receptor staining on the cellular basal membrane. The polarization of GC-A receptors was lost in the ischemic kidney. The maximal binding capacity of 125I-atrial natriuretic factor (ANF) to the basal membrane of the inner medullary cell line mIMCD-K2 was five times greater than that to the apical membrane. ANF or C-type natriuretic peptide (CNP) added to the basal side of cultured cells resulted in cGMP formation that was greater than when applied to the apical side. Depletion of ATP stores in cultured cells was followed by an increase of 125I-ANF binding to apical cellular membranes. Similar results were obtained when receptor guanylyl cyclase activity was assayed. In conclusion, these results suggest that functional GC-A and GC-B receptors are present predominantly on the basal membrane of IMCD. However, depletion of cellular ATP stores such as in ischemia is followed by a partial loss of polarization. 

Received 28 April 1995; accepted in final form 15 June 1995.
APS Manuscript Number F142-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 11 July 1995.