AJP - Heart and Circulatory Physiology, Vol 259, Issue 3 759-H765, Copyright © 1990 by American Physiological Society
Inosine transiently decreases coronary flow but potentiates vasodilation by adenosine
P. Van der Meer and J. W. de Jong
Thoraxcenter, Erasmus University Rotterdam, The Netherlands.
To test whether inosine interferes with the action of adenosine, we
investigated the effects of intracoronary administration of inosine,
adenosine, 8-phenyltheophylline, and adenosine deaminase on isolated rat
heart. Inosine did not change heart rate or developed tension but increased
the effluent adenosine concentration. Inosine also decreased exogenous
adenosine uptake and breakdown. After the start of the inosine infusion (20
microM), a transient 30% decrease of coronary flow took place within 0.5
min. The nucleoside caused sustained vasodilation, dependent on the
concentration (30-400 microM). After the infusion we observed a transient
vasodilation. A nonvasoactive inosine concentration (10 microM) combined
with an adenosine concentration that increased flow by 60% (0.1 microM)
raised vasodilation by another 60%. Infusion of adenosine, adenosine
deaminase, or 8-phenyltheopylline did not influence the inosine-induced
transient decrease of flow, suggesting that this decrease is independent of
adenosine and its receptor. We conclude that inosine 1) potentiates the
vasodilation induced by adenosine and 2) is a coronary vasodilator but
probably also a vasoconstrictor.
