Potassium depletion improves myocardial potassium uptake in vivo

Am J Physiol Cell Physiol. 2004 Jul;287(1):C135-41. doi: 10.1152/ajpcell.00580.2003. Epub 2004 Mar 3.

Abstract

Potassium depletion (KD) is a very common clinical entity often associated with adverse cardiac effects. KD is generally considered to reduce muscular Na-K-ATPase density and secondarily reduce K uptake capacity. In KD rats we evaluated myocardial Na-K-ATPase density, ion content, and myocardial K reuptake. KD for 2 wk reduced plasma K to 1.8 +/- 0.1 vs. 3.5 +/- 0.2 mM in controls (P < 0.01, n = 7), myocardial K to 80 +/- 1 vs. 86 +/- 1 micromol/g wet wt (P < 0.05, n = 7), increased Mg, and induced a tendency to increased Na. Myocardial Na-K-ATPase alpha(2)-subunit abundance was reduced by approximately 30%, whereas increases in alpha(1)- and K-dependent pNPPase activity of 24% (n = 6) and 13% (n = 6), respectively, were seen. This indicates an overall upregulation of the myocardial Na-K pump pool. KD rats tolerated a higher intravenous KCl dose. KCl infusion until animals died increased myocardial K by 34% in KD rats and 18% in controls (P < 0.05, n = 6 for both) but did not induce different net K uptake rates between groups. However, clamping plasma K at approximately 5.5 mM by KCl infusion caused a higher net K uptake rate in KD rats (0.22 +/- 0.04 vs. 0.10 +/- 0.03 micromol x g wet wt(-1) x min(-1); P < 0.05, n = 8). In conclusion, a minor KD-induced decrease in myocardial K increased Na-K pump density and in vivo increased K tolerance and net myocardial K uptake rate during K repletion. Thus the heart is protected from major K losses and accumulates considerable amounts of K during exposure to high plasma K. This is of clinical interest, because a therapeutically induced rise in myocardial K may affect contractility and impulse generation-propagation and may attenuate increased myocardial Na, the hallmark of heart failure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Dose-Response Relationship, Drug
  • Enzyme Inhibitors / pharmacology
  • Female
  • Magnesium / metabolism
  • Myocardium / metabolism*
  • Ouabain / pharmacology
  • Potassium / antagonists & inhibitors*
  • Potassium / blood
  • Potassium / metabolism
  • Potassium / pharmacokinetics*
  • Potassium Chloride / pharmacology
  • Rats
  • Rats, Wistar
  • Sodium / metabolism
  • Sodium-Potassium-Exchanging ATPase / metabolism

Substances

  • Enzyme Inhibitors
  • Ouabain
  • Potassium Chloride
  • Sodium
  • Sodium-Potassium-Exchanging ATPase
  • Magnesium
  • Potassium