Effect of local intra-arterial NG-monomethyl-L-arginine in patients with hypertension: the nitric oxide dilator mechanism appears abnormal

J Hypertens. 1992 Sep;10(9):1025-31.

Abstract

Objective: There is indirect evidence that the nitric oxide system may be impaired in hypertensive patients. The objective of this study was to examine basal nitric oxide-mediated dilation in hypertensive patients.

Design: The forearm blood flow (FBF) response to noradrenaline and NG-monomethyl-L-arginine (L-NMMA), a stereospecific inhibitor of nitric oxide synthesis, was compared in seven untreated hypertensive patients and 17 normotensive controls.

Methods: Drugs were infused locally into the brachial artery and FBF measured using venous occlusion plethysmography.

Results: In normotensives noradrenaline (60, 120 and 240 pmol/min) and L-NMMA (1,2 and 4 mumol/min) produced similar reductions in resting FBF. In the hypertensives L-NMMA was significantly less effective than noradrenaline, such that the threshold dose for L-NMMA vasoconstriction was increased and the overall response to L-NMMA reduced. Furthermore, when noradrenaline was used as an internal control there was a significant negative relationship between the response to L-NMMA and blood pressure. When the responses to L-NMMA and noradrenaline were compared between groups, the response to L-NMMA was significantly less in hypertensives compared with normotensives, whereas there was no statistical difference in the response to noradrenaline between the two groups.

Conclusions: The results suggest an abnormality of basal nitric oxide-mediated dilation in the forearm arteriolar bed of patients with untreated essential hypertension.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Arginine / analogs & derivatives*
  • Arginine / pharmacology
  • Blood Pressure / drug effects
  • Dose-Response Relationship, Drug
  • Female
  • Forearm / blood supply
  • Humans
  • Hypertension / physiopathology*
  • Male
  • Middle Aged
  • Nitric Oxide / metabolism*
  • Norepinephrine / pharmacology*
  • Reference Values
  • Regional Blood Flow / drug effects
  • Vasodilation / drug effects*
  • omega-N-Methylarginine

Substances

  • omega-N-Methylarginine
  • Nitric Oxide
  • Arginine
  • Norepinephrine