Referenced in: none

Automatically associated channels: Kir1.1 , Kir6.2

Title: Developmental expression of ROMK mRNA in rabbit cortical collecting duct.

Authors: C Benchimol, B Zavilowitz, L M Satlin

Journal, date & volume: Pediatr. Res., 2000 Jan , 47, 46-52

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/10625082

Abstract
The cortical collecting duct (CCD) is a major site of regulation of K+ homeostasis in the fully differentiated mammalian kidney. CCDs isolated from adult rabbits and microperfused in vitro secrete K+ into the tubular fluid at high rates. However, CCDs dissected from newborn animals show no significant net K+ secretion until the 3rd wk of life, at least in part because of a paucity of conducting apical secretory K+ (SK) channels. To determine whether the abundance of genes encoding the SK channel is developmentally regulated, we used reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot analysis to test for the presence of mRNA encoding rat outer medullary K+ channel (ROMK), considered to be a major subunit of the SK channel, in kidney and single CCDs isolated from maturing rabbits. Using rat ROMK-specific primers, RT-PCR of rabbit kidney yielded an amplification product of expected size and sequence. Northern blot analysis identified a single band at approximately 2.9 kb in kidney at all ages. Densitometric analysis revealed a progressive increase in steady state expression of ROMK message in kidney after birth. RT-PCR of individual CCDs yielded a single band of predicted size for ROMK in all segments isolated from animals > or =3 wk old. In contrast, transcripts were not detected in any CCD samples obtained from 1-wk-old animals and were identified in only 30% of CCD samples isolated from 2-wk-old rabbits. In all of the latter tubular samples, a specific PCR product of correct size for beta-actin mRNA was detected. These results suggest that an increase in steady state expression of ROMK mRNA contributes to the developmental appearance of conducting secretory K+ channels in the CCD.