Angiotensin II and angiotensin-(1-7) effects on free cytosolic sodium, intracellular pH, and the Na+-H+ antiporter in vascular smooth muscle

Minghao Ye, Guillermo Flores, Daniel Batlle*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

The aim of the present study was to define the effects of angiotensin II (Ang II) and Ang-(1-7) on free cytosolic Na+ (Na+(i)), intracellular pH (pH(i)), and the Na+-H+ antiporter in cultured vascular smooth muscle cells from rat aorta. Cells were loaded with either BCECF-AM or SBFI-AM for measurement of pH(i) and Na+(i), respectively. Ang II (10-6 mol/L) caused a rapid rise in Na+(i), followed by a progressive increase that peaked at about 10 minutes (from 11±1.5 to 16±1.5 mmol/L, P<.001), whereas Ang-(1-7) (10-6 mol/L) did not affect Na+(i), significantly (from 11.5±1.1 to 11.8±0.07 mmol/L). The effect of Ang II on Na+, was concentration dependent (ΔNa+, 5.1±0.9, 3.8±0.6, and 0.14±0.18 mmol/L, with decreasing concentrations of 10-6, 10-7, 10-8, and 10-9 mol/L, respectively). Ang II caused a brief acidification followed by an increase in pH(i) (from 7.34±0.03 to 7.43±0.03 after 10 minutes, P<.005), and Ang-(1.-7) had no significant effect on pH(i) (from 7.23±0.03 to 7.23±0.03). To investigate whether pH(i) and Na+(i) changes induced by Ang II were due to cell Na+ entry via stimulation of the Na+-H+ antiporter, we pretreated cells with EIPA (25 μmol/L) or ouabain (2.0 mmol/L). Ang II in the presence of ouabain caused a greater increase than that seen with ouabain alone (ΔNa+(i), 13±1.5 versus 6.3±1.2 mmol/L, P<.0025). EIPA by itself decreased Na+, and pH(i). After EIPA, Ang II failed to increase both Na+, and pH(i), demonstrating that the Na+-H+ antiporter is responsible for the rises in Na+(i) and pH(i) during stimulation with Ang II. To further characterize the mechanism of Ang II action, we exposed cells to an Ang II type I receptor antagonist (L-158,809, 10-6 mol/L) or two different type 2 receptor antagonists (PD 123177 and CGP 421112A, 10-6 mol/L). L-158,809 completely blocked the rise in pH(i) caused by Ang II, whereas PD 123177 and CGP 421112A did not. We conclude that Ang II increases both Na+(i) and pH(i), and both effects are mediated by stimulation of the Na+-H+ antiporter. Ang-(1-7), by contrast, has no significant effect on Na+(i), pH(i), or the Na+-H+ antiporter. Stimulation of this antiporter by Ang II is exerted through the type I receptor.

Original languageEnglish (US)
Pages (from-to)72-78
Number of pages7
JournalHypertension
Volume27
Issue number1
DOIs
StatePublished - Jan 1 1996

Keywords

  • angiotensin
  • muscle, smooth, vascular
  • sodium/hydrogen antiporter

ASJC Scopus subject areas

  • Internal Medicine

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