The effects of ischemic and adenosine preconditioning on
interstitial fluid adenosine and myocardial infarct size.
Lasley, Robert D., Patrick J. Konyn, Julia O. Hegge, and Robert M.
Mentzer, Jr.
Department of Surgery, University of Wisconsin, Madison, WI
APStracts 2:0184H, 1995.
The accumulation of adenosine during a brief coronary occlusion has
been proposed to mediate the infarct size limiting effect of ischemic
preconditioning. The purpose of this study was to compare the effects
of ischemic preconditioning and a transient adenosine infusion on
myocardial interstitial fluid (ISF) adenosine levels and infarct
size. Microdialysis fibers (10.0 mm length) were placed in the left
ventricular myocardium of pentobarbital anesthetized rabbits to
estimate ISF adenosine. Ischemic preconditioning was induced by 5
minutes coronary artery occlusion and 10 minutes reperfusion prior to
45 minutes occlusion. Adenosine preconditioning was induced with 5
minutes intravenous adenosine infusion (140 _g/kg/min) followed by 10
minutes washout prior to the prolonged occlusion. Myocardial infarct
size was determined by triphenyltetrazolium chloride (TTC) staining
after 3 hours reperfusion. Five minutes ischemia and 5 minutes
adenosine infusion produced comparable increases in dialysate
adenosine levels (from 0.19+0.02 to 0.69+0.11 _M and 0.28+0.10 to
0.71+0.18 _M, respectively), which decreased to baseline prior to the
prolonged ischemia, however ischemic preconditioned hearts exhibited
elevated dialysate adenosine levels for the first 5 minutes
reperfusion. Ischemic preconditioned hearts exhibited significantly
reduced dialysate adenosine concentrations for the first 20 minutes
of the prolonged occlusion (p< 0.05 vs control), and infarct size
was reduced from 41+6% of risk area to 10+4%. Adenosine
preconditioning had no effect on dialysate adenosine levels during
prolonged ischemia but did reduce infarct size to 25+5% of risk area.
These results indicate that a transient increase in ISF adenosine can
reduce myocardial infarct size, but adenosine alone does not fully
replicate the protective effects of ischemic preconditioning.
Received 23 January 1995; accepted in final form 20 April 1995.
APS Manuscript Number H57-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.