Cholesterol enrichment inhibits Na+/K+ pump in endothelial cells

Ying Tung Lau*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

15 Scopus citations

Abstract

We have previously shown that cholesterol enrichment reduces 3H-ouabain binding in cultured vascular endothelial cells. The present study aimed to determine the effect of cholesterol enrichment on ouabain-sensitive 86Rb (as a substitute for K+) influx, i.e. K+ transport via the pump, and to examine whether cellular K+ content was affected in human umbilical vein endothelial cells. 86Rb influx was inhibited by both ouabain and bumetanide in a dose-dependent manner. Consistent with an earlier report [1], inhibition achieved was greater for ouabain (∼ 70% at mM range) than for bumetanide (∼ 55% at 0.1 mM), indicating that K+ influx via Na+/K+ pump was greater than that via Na+K+Cl- cotransport in these cells. After incubation of 18 h or more with cholesterol-enriched liposomes (2:1 cholesterol to phospholipid ratio), a significant reduction (>20%) of the ouabain-sensitive K+ influx and an increase in cellular cholesterol content were observed. The inhibitory effect was observed only at liposome concentrations above 2 mg/ml. Following 18 h incubation with 2 mg/ml cholesterol-enriched liposomes, cellular K+ content was significantly decreased. The phospholipid liposome treatment did not alter K+ content, suggesting that the inhibitory effect on Na+/K+ pump and the cellular K+ content reduction was not due to liposome fusion alone or to the phospholipid present. These findings indicate that cholesterol enrichment inhibits Na+/K+ pump and thus reduces cellular K+ content in endothelial cells, and may play a role in the widely observed abnormal endothelium-dependent vascular response induced by hypercholesterolemia.

Original languageEnglish
Pages (from-to)251-257
Number of pages7
JournalAtherosclerosis
Volume110
Issue number2
DOIs
StatePublished - 10 1994

Keywords

  • Cellular K content
  • Cholesterol
  • Endothelial cells
  • Na/K pump

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