Effect of dietary K intake on apical small-conductance K channel in CCD: role of protein tyrosine kinase.
We have used Western blot to examine the expression of cSrc protein tyrosine kinase (PTK) and protein tyrosine phosphatase (PTP)-1D in the renal cortex, and the patch-clamp technique to determine the role of PTK in mediating the effect of dietary K intake on the small-conductance K (SK) channel in the cortical collecting duct (CCD). When rats were on a K-deficient (KD) diet for 1, 3, 5, and 7 days, the expression of cSrc increased by 40, 90, 140, and 135%, respectively. In contrast, the expression of cSrc in the renal cortex from rats on a high-K (HK) diet for 1, 2, and 3 days decreased by 40, 60, and 75%, respectively. However, the protein level of PTP-1D was not significantly changed by dietary K intake. The addition of 1 microM herbimycin A increased NP(o), a product of channel number (N) and open probability (P(o)) in the CCD from rats on a normal diet or on a KD diet. The increase in NP(o) was 0.30 (normal), 0.45 (1-day KD), 0.65 (3-day KD), 1.55 (5-day KD), and 1.85 (7-day KD), respectively. Treatment of the CCD with herbimycin A from rats on a KD diet increased NP(o) per patch from the control value (0.7) to 1.4 (1-day KD), 1.6 (3-day KD), 2.6 (5-day KD), and 3.5 (7-day KD), respectively. In contrast, HK intake for as short as 1 day abolished the effect of herbimycin A. Furthermore, the expression of ROMK channels in the renal cortex was the same between rats on a KD diet or on a HK diet. Moreover, treatment with herbimycin A did not further increase NP(o) in the CCDs from rats on a HK diet. We conclude that dietary K intake plays a key role in regulating the activity of the SK channels and that PTK is involved in mediating the effect of the K intake on channel activity in the CCD.
Wei
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Y
Department of Pharmacology, New York Medical College, Valhalla, New York 10595, USA. wenhui_wang@nymc.edu
Bloom
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Lin
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D
Gu
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Wang
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WH
D000818:Animals; D016227:Benzoquinones; D016764:Cell Polarity; D004032:Diet; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D016391:Genes, src; D015151:Immunoblotting; D007685:Kidney Tubules, Collecting / Q000187:drug effects / Q000502:physiology*; D047029:Lactams, Macrocyclic; D008297:Male; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000008:administration & dosage* / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011809:Quinones / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017828:Rifabutin / Q000031:analogs & derivatives
D016227:Benzoquinones; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D015221:Potassium Channels; D011809:Quinones; D017828:Rifabutin; C020754:herbimycin; D011505:Protein-Tyrosine Kinases; D011188:Potassium