NDLI: $K^{+}$ secretion in the rat kidney: $Na^{+}$ channel-dependent and -independent mechanisms

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Frindt, Gustavo Palmer, Lawrence G.
Description	Country affiliation: United States Author Affiliation: Frindt G ( Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, New York 10065, USA.)
Abstract	Renal Na(+) and K(+) excretion was measured in rats with varying dietary K(+) intake. The requirement for channel-mediated distal nephron Na(+) reabsorption was assessed by infusing the animals with the K(+)-sparing diuretic amiloride via osmotic minipumps. At infusion rates of 2 nmol/min, the concentration of amiloride in the urine was 38 microM, corresponding to concentrations of 9-23 microM in the distal tubular fluid, sufficient to block >98% of Na(+) transport through apical Na(+) channels (ENaC). With a control K(+) intake (0.6% KCl), amiloride reduced K(+) excretion rates (U(K)V) from 0.85 +/- 0.15 to 0.05 +/- 0.01 micromol/min during the first 2 h of infusion, suggesting that distal nephron K(+) secretion was completely dependent on the activity of Na(+) channels. When K(+) intake was increased by feeding overnight with a diet containing 10% KCl, amiloride reduced U(K)V from 7.5 +/- 0.7 to 1.3 +/- 0.1 micromol/min despite an increased plasma K(+) of 9 mM, again suggesting a major but not exclusive role for the Na(+) channel-dependent pathway of K(+) secretion. The maximal measured rates of amiloride-sensitive K(+) excretion correspond well with estimates based on apical K(+) channel activity in distal nephron segments. However, when the animals were adapted to the high-K(+) diet for 7-9 days, the diuretic decreased U(K)V less, from 6.1 +/- 0.6 to 3.0 +/- 0.8 micromol/min, indicating an increasing fraction of K(+) excretion that was independent of Na(+) channels. This indicates the upregulation of a Na(+) channel-independent mechanism for secreting K(+).
File Format	HTM / HTML
ISSN	1931857X
e-ISSN	15221466
DOI	10.1152/ajprenal.90528.2008
Journal	AJP: Renal Physiology
Issue Number	2
Volume Number	297
Language	English
Publisher	American Physiological Society
Publisher Date	2009-08-01
Publisher Place	United States
Access Restriction	Open
Subject Keyword	Adaptation, Physiological Research Support, N.i.h., Extramural Sodium, Dietary Potassium, Dietary Aldosterone Blood Discipline Physiology Epithelial Sodium Channels Amiloride Biological Transport Time Factors Diet, Sodium-restricted Urine Glomerular Filtration Rate Infusion Pumps, Implantable Secretion Rats, Sprague-dawley Discipline Nephrology Administration & Dosage Metabolism Drug Effects Nephrons Potassium Channels Urodynamics Animals Sodium Kinetics Natriuresis Sodium Channel Blockers Potassium
Content Type	Text
Resource Type	Article
Subject	Physiology Urology

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