Inotropic effects of histamine in human myocardium: differentiation between positive and negative components

J Cardiovasc Pharmacol. Nov-Dec 1984;6(6):1210-5.

Abstract

Histamine is known to enhance the contractility of the human myocardium in vitro. We have observed that when the H2-receptor antagonist cimetidine (or ranitidine) blocks the positive inotropic effect of histamine in spontaneously beating pectinate muscles isolated from human right atrial appendage, a negative inotropic effect is unmasked. This decrease in contractility is independent of changes in rate, as it occurs in preparations paced at constant rate, is mimicked by the H1-receptor agonist 2-(2-thiazolyl)-ethylamine (ThEA) and is abolished by the H1-antagonist pyrilamine. Thus, the negative inotropic effect of histamine appears to be mediated by H1-receptors. Our data indicate that the inotropic response of the human myocardium to histamine consists of two opposing components: an increase in contraction, mediated by H2-receptors, and a decrease in contraction, mediated by H1-receptors. Given the widespread use of H2-blockers and the multitude of clinical conditions in which histamine is released, there may well be circumstances in which an H1-response predominates. This could result in a decrease in myocardial contractility.

Publication types

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

MeSH terms

  • Cimetidine / pharmacology
  • Histamine / pharmacology*
  • Humans
  • Imidazoles / pharmacology
  • Impromidine
  • In Vitro Techniques
  • Myocardial Contraction / drug effects*
  • Norepinephrine / pharmacology
  • Pyrilamine / pharmacology
  • Ranitidine / pharmacology
  • Receptors, Histamine H1 / drug effects
  • Receptors, Histamine H2 / drug effects
  • Thiazoles / pharmacology
  • Time Factors

Substances

  • Imidazoles
  • Receptors, Histamine H1
  • Receptors, Histamine H2
  • Thiazoles
  • 2-(2-aminoethyl)thiazole
  • Cimetidine
  • Histamine
  • Ranitidine
  • Impromidine
  • Pyrilamine
  • Norepinephrine