Cell-specific expression of amiloride-sensitive, na+-conducting ion channels in the kidney. Ciampolillo, Flora, David E. McCoy, Ryan B. Green, Katherine H. Karlson, Andre Dagenais, Robert S. Molday, and Bruce A. Stanton. Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03755; Centre de Recherche, Hotel-Dieu de Montreal, Montreal, Quebec, Canada, H2W 1T8; and Department of Biochemistry, University of British Columbia, Vancouver, B.C. Canada V6T 1W
APStracts 3:0154C, 1996.
Amiloride-sensitive, electrogenic Na+ absorption across the distal nephron plays a vital role in regulating extracellular fluid volume and blood pressure. Recently, two amiloride-sensitive, Na+-conducting ion channel cDNAs were cloned. One, an epithelial Na+-selective channel (ENaC), is responsible for Na+ absorption throughout the distal nephron. The second, a cGMP-inhibitable cation channel, is conductive to Na+ and Ca2+ and contributes to Na+ absorption across the inner medullary collecting duct (IMCD). As a first step toward understanding the segment-specific contributions(s) of cGMP-gated cation channels and ENaC to Na+ and Ca2+ uptake along the nephron, we used in situ RT-PCR hybridization, solution phase RT-PCR, and Western Blot analysis to examine the nephron and cell-specific expression of these channels in mouse kidney cell lines and/or dissected nephron segments. cGMP-gated cation channel mRNA was detected in proximal tubule (PT), medullary thick ascending limb (mTAL), distal convoluted tubule (DCT), cortical collecting duct (CCD), outer medullary collecting duct (OMCD) and IMCD. cGMP-gated cation channel protein was detected in DCT, CCD and IMCD cell lines. These observations suggest that hormones that modulate intracellular cGMP levels may regulate Na+, and perhaps Ca2+, uptake throughout the nephron. mRNA for [alpha]-mENaC, a subunit of the mouse ENaC, was detected in mTAL, DCT, CCD, OMCD and IMCD. Coexpression of [alpha]-mENaC and cGMP-gated cation channel mRNAs in mTAL, DCT, CCD, OMCD and IMCD suggests that both channels may contribute to Na+ absorption in these nephron segments. 

Received 21 February 1996; accepted in final form 6 May 1996.
APS Manuscript Number C91-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96