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Blood flow and ultrastructure in ischemic myocardium of cats given dexamethasone
Insights
Dexamethasone did not improve blood flow in ischemic heart tissue and failed to preserve myocardial structure after reperfusion in cats. The steroid may offer some stabilization during ischemia but not during reperfusion.
Area of Science:
- Cardiovascular Research
- Pharmacology
- Myocardial Ischemia
Background:
- Myocardial ischemia and reperfusion injury remain significant clinical challenges.
- Understanding the effects of pharmacological interventions on myocardial tissue is crucial.
Purpose of the Study:
- To investigate the impact of dexamethasone sodium phosphate on regional myocardial blood flow, creatine kinase activity, and ultrastructure during coronary artery ligation and reperfusion in a feline model.
Main Methods:
- Anesthetized cats underwent sham operation, coronary artery ligation, or ligation with reperfusion.
- Dexamethasone sodium phosphate was administered prior to ligation in experimental groups.
- Regional myocardial blood flow, creatine kinase activity, and myocardial ultrastructure were assessed.
Main Results:
- Coronary artery ligation significantly reduced myocardial blood flow (52-92%) in the posterior basal myocardium.
- Dexamethasone pretreatment did not prevent the loss of creatine kinase activity following ligation.
- Steroid treatment was ineffective in maintaining myocardial ultrastructure in reperfused tissue.
Conclusions:
- Dexamethasone does not enhance blood flow in ischemic or reperfused myocardial tissue.
- While dexamethasone may offer some stabilization during ischemia, it fails to preserve myocardial ultrastructure upon reperfusion in moderately to severely ischemic regions.
Abstract:
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.