Effects of adenosine in simulated ischemia and reperfusion in
guinea pig ventricular myocytes..
Cordeiro, Jm, Gr Ferrier, and Se Howlett.
Department of Pharmacology, Dalhousie University, Halifax, Nova
Scotia, Canada.
APStracts 2:0042H, 1995.
Effects of adenosine on cardiac cellular electrical and contractile
activity were determined during ischemia and reperfusion. Electrical
activity was recorded with conventional and voltage clamp techniques.
Contractions were monitored with a video edge detector. Myocytes were
exposed to simulated ischemia (20 min), in the presence or absence of
adenosine (1-50[mu]M), and reperfused with Tyrode's solution. Adenosine
had no effects under control conditions. However, action potential
abbreviation during ischemia was greater in the presence of adenosine
than control, and recovery was delayed. In ischemia, ICa declined
equally and contractions were abolished in control and adenosine
-treated myocytes. In early reperfusion, oscillatory afterpotentials
(OAP), transient inward current (ITI), and aftercontractions appeared
and contractions increased above pre-ischemic levels. Adenosine
abolished contractile overshoot and reduced incidence of OAP, ITI and
aftercontractions from 78% to 37.5%. The effects of exogenous
adenosine were inhibited by A1 receptor blockade. Inhibition of
endogenous adenosine by 8-phenyltheophylline only increased incidence
of ITI. Thus, exogenous adenosine in ischemia may protect the
myocardium in reperfusion via A1 adenosine receptors.
Received 18 February 1994; accepted in final form 27 January
1995.
APS Manuscript Number H165-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.