Cellular localization, membrane distribution, and possible function of guanylyl cyclases A and 1 in collecting ducts of rat

Background: Natriuretic peptides regulate Na+ and H2O transport in the cort ical collecting duct (CCD). We have shown that natriuretic peptides have no effect on ion conductances or water transport of principal cells (PC) even though a cGMP-regulated K+ channel is located in the basolateral membrane of these cells. Methods: RT-PCR was used to screen for different guanylyl c yclases (GC) in CCD and to look for the expression of GC-1 and GC-A mRNA in CCD of male and female Wistar and Sprague-Dawley rats. Polyclonal antibodi es were raised against the detected GC. BCECF was used to investigate the e ffects of ANP on intracellular pH in intercalated cells (IC). Results: GC-A and GC-1 were detected. GC-A was immunolocalized in the luminal membrane o f IC while GC-I was mainly found in the luminal membrane of PC. GC-1 is exp ressed in Sprague-Dawley and Wistar rats except for male Sprague-Dawley rat s, while GC-A is expressed in all strains. ANP (160 nM, n = 11), urodilatin (140 nM, n = 6), which had no effect in PC, significantly decreased pH(i) by 0.02 +/-0.01 and 0.03 +/-0.01 Units in IC, respectively. ANP as well as urodilatin and 8-Br-cGMP decreased the pH, recovery after acidification by 30 +/-6% (n=12), 37 +/-7% (n=8), and 19 +/-3% (n=8), respectively. Conclusi on: GC-A is located in the luminal membrane of IC of rat CCD and ANP acts t hrough this receptor when regulating pH, via an inhibition of the Na+/H+-ex changer. PC do not possess GC-A. GC-1 seems to be the only GC in these cell s of most rat strains tested and therefore, it could be responsible for the regulation of K+ channels in the basolateral membrane via cGMP-dependent p rotein kinase. (C) 2000 Elsevier Science BY. All rights reserved.