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Differential antagonism of cardiac actions of adenosine by theophylline

B D Bertolet1, L Belardinelli, K Avasarala

  • 1Department of Medicine, University of Florida Health Sciences Center, Gainesvilla 32610-0277, USA.

Cardiovascular Research
|November 1, 1996
PubMed

Insights

Theophylline fully blocks adenosine

Area of Science:

  • Cardiology
  • Pharmacology
  • Adenosine Receptor Research

Background:

  • Adenosine receptors (A1 and A2) play crucial roles in cardiac function and coronary blood flow.
  • Theophylline is a non-selective adenosine receptor antagonist with known cardiovascular effects.

Purpose of the Study:

  • To compare the sensitivity of cardiac A1- and A2-adenosine receptor effects to theophylline antagonism in humans.
  • To elucidate the differential impact of theophylline on A1-mediated A-H interval prolongation and A2-mediated coronary vasodilation.

Main Methods:

  • Human study: Assessed A-H interval (A1) and coronary blood flow (A2) responses to adenosine before and after theophylline administration in 10 patients.
  • Animal study: Evaluated A1 and A2 receptor effects in isolated guinea pig hearts with varying theophylline and adenosine concentrations.

Main Results:

  • In humans, theophylline completely inhibited adenosine-induced A-H interval prolongation (A1 effect).
  • Theophylline showed minimal impact on adenosine-induced coronary vasodilation (A2 effect), especially at higher adenosine concentrations (>1.0 microM).
  • Guinea pig heart studies confirmed that theophylline's antagonism of A2 effects was concentration-dependent and less effective at higher adenosine levels.

Conclusions:

  • Theophylline demonstrates complete antagonism of cardiac A1-adenosine receptor effects in humans.
  • Theophylline exhibits minimal antagonism of cardiac A2-adenosine receptor-mediated coronary vasodilation in humans, particularly under conditions of elevated adenosine concentrations.
Abstract

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