Differential regulation of ROMK expression in kidney cortex and medulla by aldosterone and potassium

Abstract

This study explores the role of K+ and aldosterone in the regulation of mRNA of the ATP-sensitive, inwardly rectifying K+ channel, ROMK, in the rat kidney. K+ deficiency downregulated ROMK mRNA in cortex to 47.1 ± 5.1% of control ( P < 0.001) and in medulla to 56.1 ± 3.4% ( P < 0.001). High-K+ diet slightly increased ROMK mRNA in medulla to 122 ± 9% ( P < 0.05 vs. control). Adrenalectomy (Adx) downregulated cortical ROMK mRNA to 30.7 ± 6.8% ( P < 0.001 vs. control), and increased it in medulla to 138 ± 12.9% ( P < 0.02 vs. control). In Adx rats, K+ deficiency decreased ROMK mRNA in cortex and medulla similar to intact rats. The α1- and β1-Na-K-ATPase subunits were regulated in parallel to that of ROMK. In medulla, ROMK mRNA correlated with serum K+ concentration at R = 0.9406 ( n = 6, P < 0.001) and α1-Na-K-ATPase mRNA at R = 0.9756 ( n = 6, P < 0.001). ROMK2 also correlated with serum K+ concentration ( R = 0.895; n = 6, P < 0.01). These results show that cortical ROMK expression is regulated by aldosterone and K+, whereas the medullary ROMK mRNA is regulated by serum K+.

Mineralocorticoid receptor is involved in rat and human ocular chorioretinopathy

“…Since aldosterone/MR activation is known to modulate ion channel expression in other tissues (16)(17)(18), we reasoned that KCa2.3 might be involved in aldosterone/MR-induced choroidal vasodilation. Immunolocalization showed that KCa2.3 expression in rat retinas was restricted to the endothelial cells of choroid vessels (Figure 2, A-C, and Supplemental Figure 4).…”

Hypertension of Kcnmb1 −/− is linked to deficient K secretion and aldosteronism

“…However, it has been difficult to distinguish the individual roles of BK and ROMK channels with respect to secreting K in direct response to elevated K or increased aldosterone. In the CCD (27) and the CNT (28), ROMK is up-regulated in the apical membrane by a high K diet. Aldosterone increases ROMK in the apical membrane of the rat CCD (29).…”

Potassium excretion during antinatriuresis: perspective from a distal nephron model

“…In the current work, entering CNT Na ϩ is close to 45 mM at baseline, and the impact on CNT K ϩ secretion with doubling of ROMK was on the order of 10%. This should not be taken to discount the significance of chronic dietary K ϩ in modulating ROMK expression (47), but it is outside the focus of the model calculations in this work. Of note, comparing FHH mice with control, there seemed to be little difference of ROMK expression on low-or high-K ϩ diets (20).…”