α1- and α2-adrenergic responsiveness in human skeletal muscle feed arteries: the role of TRPV ion channels in heat-induced sympatholysis

Am J Physiol Heart Circ Physiol. 2014 Nov 1;307(9):H1288-97. doi: 10.1152/ajpheart.00068.2014.

Abstract

The purpose of this study was to determine if heat inhibits α2-adrenergic vasocontraction, similarly to α1-adrenergic contraction, in isolated human skeletal muscle feed arteries (SMFA) and elucidate the role of the temperature-sensitive vanilloid-type transient receptor potential (TRPV) ion channels in this response. Isolated SMFA from 37 subjects were studied using wire myography. α1 [Phenylephrine (PE)]- and α2 [dexmedetomidine (DEX)]-contractions were induced at 37 and 39°C with and without TRPV family and TRPV4-specific inhibition [ruthenium red (RR) and RN-1734, respectively]. Endothelial function [acetylcholine (ACh)] and smooth muscle function [sodium nitroprusside (SNP) and potassium chloride (KCl)] were also assessed under these conditions. Heat and TRPV inhibition was further examined in endothelium-denuded arteries. Contraction data are reported as a percentage of maximal contraction elicited by 100 mM KCl (LTmax). DEX elicited a small and variable contractile response, one-fifth the magnitude of PE, which was not as clearly attenuated when heated from 37 to 39°C (12 ± 4 to 6 ± 2% LTmax; P = 0.18) as were PE-induced contractions (59 ± 5 to 24 ± 4% LTmax; P < 0.05). Both forms of TRPV inhibition restored PE-induced contraction at 39°C (P < 0.05) implicating these channels, particularly the TRPV4 channels, in the heat-induced attenuation of α1-adrenergic vasocontraction. TRPV inhibition significantly blunted ACh relaxation while denudation prevented heat-induced sympatholysis without having an additive effect when combined with TRPV inhibition. In conclusion, physiological increases in temperature elicit a sympatholysis-like inhibition of α1-adrenergic vasocontraction in human SMFA that appears to be mediated by endothelial TRPV4 ion channels.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Acetylcholine / pharmacology
  • Adrenergic alpha-1 Receptor Agonists / pharmacology*
  • Adrenergic alpha-2 Receptor Agonists / pharmacology*
  • Adult
  • Aged
  • Arteries / cytology
  • Arteries / metabolism
  • Arteries / physiology
  • Dexmedetomidine / pharmacology
  • Female
  • Hot Temperature
  • Humans
  • Male
  • Middle Aged
  • Muscle Contraction
  • Muscle, Skeletal / blood supply
  • Muscle, Smooth, Vascular / drug effects
  • Muscle, Smooth, Vascular / metabolism
  • Muscle, Smooth, Vascular / physiology*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / metabolism
  • Myocytes, Smooth Muscle / physiology
  • Nitroprusside / pharmacology
  • Phenylephrine / pharmacology
  • Potassium Chloride / pharmacology
  • Ruthenium Red / pharmacology
  • Sulfonamides / pharmacology
  • Sympatholytics / pharmacology*
  • TRPV Cation Channels / antagonists & inhibitors
  • TRPV Cation Channels / metabolism*
  • Vasoconstriction*

Substances

  • Adrenergic alpha-1 Receptor Agonists
  • Adrenergic alpha-2 Receptor Agonists
  • RN 1734
  • Sulfonamides
  • Sympatholytics
  • TRPV Cation Channels
  • Ruthenium Red
  • Nitroprusside
  • Phenylephrine
  • Potassium Chloride
  • Dexmedetomidine
  • Acetylcholine