AJP - Heart and Circulatory Physiology, Vol 244, Issue 2 273-H280, Copyright © 1983 by American Physiological Society
Effects of dipyridamole on postischemic vasodilation and extracellular adenosine
R. E. Klabunde
Postischemic vasodilation (PIVD) was studied in pump-perfused dog gracilis
muscles. The hemodynamic responses to 1, 3, and 5 min of ischemia were
evaluated in the presence and absence of intraarterial infusions of
dipyridamole in concentrations that inhibit cellular transport of
adenosine. Dipyridamole infusion produced concentration-dependent
reductions in vascular resistance and increased the time for 50% recovery
(t0.5) in vascular resistance by 39% following 5 min of ischemia. The t0.5
for PIVD was unaffected by dipyridamole following 1 and 3 min of ischemia.
Dipyridamole elevated tissue adenosine content two- to three-fold at 1, 3,
and 5 min of ischemia compared with saline controls. Intra-arterial
infusions of adenosine deaminase along with dipyridamole completely
prevented the dipyridamole-induced increase in tissue adenosine,
demonstrating that dipyridamole increases extracellular adenosine during
muscle ischemia. The significance of these findings is analyzed using a
two-compartment model for the distribution of adenosine. The data indicate
that a severalfold increase in interstitial adenosine content does not
alter PIVD and that the hemodynamic effects of dipyridamole following 5 min
of ischemia may be due to some mechanism other than enhanced accumulation
of adenosine.
