Dietary Ca2+ prevents NaCl-sensitive hypertension in spontaneously hypertensive rats by a sympatholytic mechanism.

Academic Article

Abstract

  • The current study tested the hypothesis that dietary Ca2+ supplementation reverses the NaCl-sensitive component of hypertension and the associated neurochemical abnormalities in the NaCl-sensitive spontaneously hypertensive rat (SHR-S). Male SHR-S were begun on one of four diets at 8 weeks of age: control (0.75% NaCl/0.68% Ca2+); high NaCl (8.00% NaCl/0.68% Ca2+); high Ca2+ (0.75% NaCl/2.00% Ca2+); and high NaCl/high Ca2+ (8.00% NaCl/2.00% Ca2+). High NaCl SHR-S (X2 weeks) had higher mean arterial pressure (MAP) (161 +/- 4 mm Hg) than controls (149 +/- 3 mm Hg; P less than .05). Supplementation with Ca2+ prevented the rise in MAP in high NaCl rats, but did not alter MAP in controls. The 8% NaCl diet elevated plasma norepinephrine and reduced anterior hypothalamic (AHA) norepinephrine stores and turnover; concomitant Ca2+ supplementation restored both plasma norepinephrine and AHA norepinephrine turnover to normal. Clonidine was microinjected into the AHA of rats maintained on the four diets for 2 weeks to test the hypothesis that dietary Ca2+ supplementation prevents the previously observed NaCl-induced upregulation of alpha 2-adrenoceptors in AHA. Clonidine caused dose-dependent decreases in MAP that were greater in high NaCl rats than in controls. The Ca2+ supplementation prevented the exaggerated depressor response to clonidine in the high NaCl group, but not in the controls. The Ca2+ supplementation had no effect on pretreatment MAP or on MAP responses to clonidine in control NaCl-resistant SHR (SHR-R) or Wistar-Kyoto (WKY) rats. Thus, dietary Ca2+ supplementation prevents the NaCl-induced exacerbation of hypertension and augmented depressor response to clonidine in SHR-S by increasing noradrenergic input to AHA, thereby preventing the upregulation of AHA alpha 2-adrenoceptors.
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    Keywords

  • Animals, Blood Pressure, Calcium, Dietary, Clonidine, Hypertension, Hypothalamus, Male, Norepinephrine, Rats, Rats, Inbred SHR, Receptors, Adrenergic, alpha, Sodium Chloride
  • Digital Object Identifier (doi)

    Author List

  • Oparil S; Wyss JM; Yang RH; Jin HK; Chen YF
  • Start Page

  • 179S
  • End Page

  • 188S
  • Volume

  • 3
  • Issue

  • 8 Pt 2