Increased barium influx and potassium current in stroke-prone spontaneously hypertensive rats

Yu Liu, Allan W. Jones, Michael Sturek

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29 Scopus citations

Abstract

Arterial potassium permeability is increased in hypertension. In this study we conducted voltage-clamp experiments to determine whether the whole-cell K+ current is increased in a Ca2+-dependent manner in aortic smooth muscle cells from stroke-prone spontaneously hypertensive rats (SHRSP). Aortic cells from Wistar-Kyoto (WKY) rats and SHRSP demonstrated an outward rectifying current elicited by depolarization. The current was carried primarily by K+, because intracellular Ca+ replacement eliminated more than 97% of the current. The current density was higher (P<.05) in SHRSP cells at positive potentials. In the presence of LaCl3 (200 μmol/L) or tetraethylammonium (10 mmol/L), the residual current was similar in WKY and SHRSP cells. Also, the current density did not differ between WKY and SHRSP cells in which the intracellular Ca2+ concentration was clamped at zero. Fura 2 ratio measurement showed similar resting myoplasmic Ca2+ concentration (Ca2+ m) in WKY and SHRSP cells (100±10 versus 117±9 nmol/L, P=.2). Under low extracellular Na+ conditions, which had a minimal effect on Ca2+ m, Ba2+ replacement of Ca2+ caused a continuous and approximately linear increase in the fura 2 ratio, which was twofold faster in SHRSP cells. Because Ca2+ pumps do not transport Ba2+ and Na+-Ca2+ exchange was inhibited by low extracellular Na+, this increase reflected unidirectional Ba2+ influx. These results suggest that (1) Ca2+-dependent K+ channel activity is increased in aortic smooth muscle cells from SHRSP, probably as a result of an increased Ca2+ influx that does not cause an increase in Ca2+ m, and (2) increased Ca2+ cycling, which may underlie the increased K+ current, may occur across the sarcolemma in SHRSP cells.

Original languageEnglish (US)
Pages (from-to)1091-1095
Number of pages5
JournalHypertension
Volume23
Issue number6
DOIs
StatePublished - Jun 1994

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Keywords

  • Barium
  • Fura-2
  • Lanthanum
  • Muscle
  • Potassium
  • Smooth
  • Tetraethylammonium compounds
  • Vascular

ASJC Scopus subject areas

  • Internal Medicine

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