AJP - Heart and Circulatory Physiology, Vol 242, Issue 1 55-H61, Copyright © 1982 by American Physiological Society
Blood flow and ultrastructure in ischemic myocardium of cats given dexamethasone
J. A. Spath Jr and R. J. Barsotti
Regional myocardial blood flow or myocardial creatine kinase activity and
ultrastructure was studied in anesthetized cats subjected to sham
operation, 5 h of circumflex-artery ligation, or 2 h of coronary-artery
ligation with 3 h of reperfusion. Sham-operated cats were given
dexamethasone sodium phosphate (8 mg/kg iv) at the beginning of the
experiment. Cats subjected to coronary-artery ligation were given steroid
or vehicle before ligation. In sham-operated cats the average blood flow in
tissue of the anterior wall was 2.11 +/- 0.37 (SER) ml.g-1.min-1. The
corresponding flow for tissue of the posterior wall was 2.22 +/- 0.42
ml.g-1.min-1. Ligation of the circumflex artery produced a range of average
blood flow in the posterior basal myocardium that was 52-92% less than that
of sham-operated cats. Within the tissue of the posterior left ventricular
wall, steroid pretreatment did not prevent loss of creatine kinase activity
after coronary-artery ligation. Moreover, steroid pretreatment was
ineffective in maintaining myocardial structure in reperfused myocardial
tissue. These results indicate that 1) dexamethasone does not effectively
increase blood flow within ischemic or reperfused myocardial tissue, and 2)
dexamethasone may stabilize ischemic myocardial tissue. However, upon
reperfusion, dexamethasone is unable to maintain myocardial ultrastructure
in moderately to severely ischemic tissue.
