Hypokalemia downregulates cardiac alpha 1 and skeletal muscle alpha 2 isoforms of Na+,K(+)-ATPase in ferrets.
K+ deficiency decreases amount of Na+,K(+)-ATPase in cardiac and skeletal muscle (SM) and differentially regulates alpha- and beta-subunit isoforms. Expression of the alpha 3 isoform during K+ deficiency is unknown, however. In the myocardium of normal adult ferrets, alpha 1 and alpha 3 isoforms are expressed. Therefore, we examined in ferrets the effects of K+ deficiency in levels of alpha- and beta-subunit isoforms. A K+ deficient diet greatly reduced plasma K+ concentrations. Tissue K+ content in myocardium remained unchanged, whereas that of SM decreased markedly. Corresponding to these changes, Na+,K(+)-ATPase enzyme activity decreased in SM but not in heart. Levels of alpha 1 in heart and alpha 2 in SM decreased, whereas those of alpha 3 in heart and alpha 1 in SM remained unchanged; beta 1 remained unchanged in both tissues. Thus, in ferrets, K+ deficiency differentially regulated the levels of Na+,K(+)-ATPase isoforms in an isoform- and tissue-dependent manner.
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Department of Pharmacology College of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
D000818:Animals; D015536:Down-Regulation; D005289:Ferrets; D007008:Hypokalemia / Q000378:metabolism*; D007527:Isoenzymes / Q000096:biosynthesis*; D008297:Male; D009132:Muscles / Q000201:enzymology / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism; D011191:Potassium Deficiency / Q000378:metabolism*; D017419:Potassium, Dietary; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis*
D007527:Isoenzymes; D017419:Potassium, Dietary; D000254:Sodium-Potassium-Exchanging ATPase