Referenced in: none

Automatically associated channels: Kir1.1

Title: Regulation by glucocorticoids and osmolality of expression of ROMK (Kir 1.1), the apical K channel of thick ascending limb.

Authors: Morgan Gallazzini, Amel Attmane-Elakeb, David B Mount, Steven C Hebert, Maurice Bichara

Journal, date & volume: Am. J. Physiol. Renal Physiol., 2003 May , 284, F977-86

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/12540364

Abstract
Mechanisms of regulation of ROMK channel mRNA and protein expression in medullary thick ascending limb (MTAL) were assessed in rat MTAL fragments incubated for 7 h. ROMK mRNA was quantified by quantitative RT-PCR and ROMK protein by immunoblotting analysis of crude membranes. Medium hyperosmolality (450 mosmol/kgH(2)O; NaCl plus urea added to isoosmotic medium) increased ROMK mRNA (P < 0.04) and protein (P < 0.006), and 10 nM dexamethasone also increased ROMK mRNA (P < 0.02). Hyperosmolality and dexamethasone had no additive effects on ROMK mRNA. NaCl alone, but not urea or mannitol, reproduced the hyperosmolality effect on ROMK mRNA. 1-Deamino-(8-d-arginine) vasopressin (1 nM) or 0.5 mM 8-bromo-cAMP had no effect per se on ROMK mRNA and protein. However, 8-bromo-cAMP abolished the stimulatory effect of dexamethasone on ROMK mRNA in the isoosmotic but not in the hyperosmotic medium (P < 0.004). In in vivo studies, the abundance of ROMK protein and mRNA increased in adrenalectomized (ADX) rats infused with dexamethasone compared with ADX rats (P < 0.02). These results establish glucocorticoids and medium NaCl concentration as direct regulators of MTAL ROMK mRNA and protein expression, which may be modulated by cAMP-dependent factors.