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Dietary K+ regulates apical membrane expression of maxi-K channels in rabbit cortical collecting duct

Authors :
Najjar, Fadi
Zhou, Hao
Morimoto, Tetsuji
Bruns, James B.
Li, Hai-Sheng
Liu, Wen
Kleyman, Thomas R.
Satlin, Lisa M.
Source :
American Journal of Physiology - Renal Physiology; October 2005, Vol. 289 Issue: 4 pF922-F932, 11p
Publication Year :
2005

Abstract

The cortical collecting duct (CCD) is a final site for regulation of K+ homeostasis. CCD K+ secretion is determined by the electrochemical gradient and apical permeability to K+. Conducting secretory K+ (SK/ROMK) and maxi-K channels are present in the apical membrane of the CCD, the former in principal cells and the latter in both principal and intercalated cells. Whereas SK channels mediate baseline K+ secretion, maxi-K channels appear to participate in flow-stimulated K+ secretion. Chronic dietary K+ loading enhances the CCD K+ secretory capacity due, in part, to an increase in SK channel density (Palmer et al., J Gen Physiol 104: 693–710, 1994). Long-term exposure of Ambystoma tigrinum to elevated K+ increases renal K+ excretion due to an increase in apical maxi-K channel density in their CDs (Stoner and Viggiano, J Membr Biol 162: 107–116, 1998). The purpose of the present study was to test whether K+ adaptation in the mammalian CCD is associated with upregulation of maxi-K channel expression. New Zealand White rabbits were fed a low (LK), control (CK), or high (HK) K+ diet for 10–14 days. Real-time PCR quantitation of message encoding maxi-K α- and β2–4-subunits in single CCDs from HK animals was greater than that detected in CK and LK animals (P < 0.05); β1-subunit was not detected in any CCD sample but was present in whole kidney. Indirect immunofluorescence microscopy revealed a predominantly intracellular distribution of α-subunits in LK kidneys. In contrast, robust apical labeling was detected primarily in α-intercalated cells in HK kidneys. In summary, K+ adaptation is associated with an increase in steady-state abundance of maxi-K channel subunit-specific mRNAs and immunodetectable apical α-subunit, the latter observation consistent with redistribution from an intracellular pool to the plasma membrane.

Details

Language :
English
ISSN :
1931857x and 15221466
Volume :
289
Issue :
4
Database :
Supplemental Index
Journal :
American Journal of Physiology - Renal Physiology
Publication Type :
Periodical
Accession number :
ejs7731380