1. Decrease in dietary K intake stimulates the generation of superoxide anions in the kidney and inhibits K secretory channels in the CCD.
- Author
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Wang ZJ, Sun P, Xing W, Pan C, Lin DH, and Wang WH
- Subjects
- Animals, Antioxidants pharmacology, Blotting, Western, Disease Models, Animal, Extracellular Signal-Regulated MAP Kinases antagonists & inhibitors, Extracellular Signal-Regulated MAP Kinases metabolism, Kidney Cortex drug effects, Kidney Tubules, Collecting drug effects, Male, Membrane Potentials, Mice, Mice, Inbred C57BL, Patch-Clamp Techniques, Phosphorylation, Potassium Deficiency blood, Potassium, Dietary administration & dosage, Potassium, Dietary blood, Protein Kinase Inhibitors pharmacology, Rats, Rats, Sprague-Dawley, Receptor, Angiotensin, Type 1 metabolism, Small-Conductance Calcium-Activated Potassium Channels drug effects, Tyrosine, p38 Mitogen-Activated Protein Kinases antagonists & inhibitors, p38 Mitogen-Activated Protein Kinases metabolism, src-Family Kinases antagonists & inhibitors, src-Family Kinases metabolism, Ion Channel Gating drug effects, Kidney Cortex metabolism, Kidney Tubules, Collecting metabolism, Potassium Deficiency metabolism, Potassium, Dietary metabolism, Small-Conductance Calcium-Activated Potassium Channels metabolism, Superoxides metabolism
- Abstract
We previously demonstrated that K depletion inhibited ROMK-like small-conductance K channels (SK) in the cortical collecting duct (CCD) and that the effect was mediated by superoxide anions that stimulated Src family protein tyrosine kinase (PTK) and mitogen-activated protein kinase (MAPK) (51). However, because animals on a K-deficient diet had a severe hypokalemia, superoxide-dependent signaling may not regulate ROMK channels under physiological conditions with a normal plasma K concentration. In the present study, we used the patch-clamp technique and Western blot to examine the effect of a moderate K restriction on ROMK-like SK channels and the role of PTK and MAPK in regulating apical K channels in the CCD of animals on a low-K diet (LK; 0.1% K). Rats and mice fed a LK diet for 7 days had a normal plasma K concentration. However, a LK intake increased the expression of angiotensin II type 1 receptor in the kidney. Moreover, patch-clamp experiments demonstrated that LK intake decreased the probability finding SK channels and channel activity defined by NP(o) (a product of channel number and open probability) in the CCD of both rat and mouse kidneys. Also, LK intake significantly stimulated the production of superoxide anions in the renal cortex and outer medulla in both rats and mice and increased superoxide level in the rat CCD. Moreover, LK intake augments the phosphorylation of p38 and ERK MAPK, the expression of c-Src and tyrosine phosphorylation of ROMK channels. However, treatment of animals with tempol abolished the effect of LK intake on MAPK and c-Src and increased ROMK channel activity in comparing with those of nontreated rats on a LK diet. Inhibiting p38 and ERK with SB202190 and PD98059 significantly stimulated SK in the CCD in rats on a LK diet. In addition, inhibition of PTK with herbimycin A activated SK channels in the CCD from rats on a LK diet. We conclude that LK intake stimulates the generation of superoxide anion and related products and that MAPK and Src family PTK play a physiological role in inhibiting apical K channels in the principal cells in response to LK intake.
- Published
- 2010
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