Metabolic and haemodynamic responses to adrenaline in normal dogs

Effects on infarct size of reperfusion and pretreatment with beta-blockade and calcium antagonists

The "mass of tissue at risk" and the myocardial infarct developed was studied in dogs subjected to either 24-h occlusion of the left anterior descending coronary artery or 2-h occlusion followed by 22-h reperfusion. The "mass of tissue at risk" was defined under anaesthesia at the time of occlusion using the microsphere technique. Twenty-four hours later the hearts were removed, sliced transversely and stained with 2,3,5-triphenyltetrazolium chloride to define the infarcted tissue. All myocardial tissue was mapped and cut into small pieces for weighing and radioactive counting. Radioactivity was present in all tissue, including the infarct. In the centre of the infarct, counts remained low and then increased very rapidly with distance just beyond the edge. Tissue at risk from infarction was taken as that with less than 15% of the peak left ventricular (non-ischaemic) counts. A linear relationship was found between the mass of the left ventricular infarct and the left ventricular "mass of tissue at risk". The effect of 22 hours reperfusion was examined by this method and expressed by a regression equation. There was a significant decrease in slope for the regression line of the reperfusion data, (p less than 0.05, analysis of covariance), indicating less infarcted tissue for each gram of underperfused tissue. None of the drug pretreatments explored had any effect on infarct size in the 24-h occlusion model. With reperfusion, propranolol and flunarizine diminished infarct size compared with reperfusion only (p less than 0.05 for reduced slope, the new slope being not significantly different from zero). The effect of diltiazem was not so marked. Thus infarct size can be reduced with pretreatment, as long as the myocardium is reperfused.

Is the rat a suitable model for studying alcoholic cardiomyopathy? Hemodynamic studies at various stages of chronic alcohol ingestion

Three groups of wistar rats with chronic alcohol consumption were studied: 10% ethanol for 6 months, 20% ethanol for 7 months, 20% ethanol for 12 months. In the intact heart in situ, left ventricular parameters of pressure, volume, and blood flow were recorded. On the average, body weight and heart weight of the alcohol-fed rats (A) were diminished by 10% as compared with controls (C). If end-diastolic volume is related to heart weight, no significant differences in the pressure-volume relations between C and A were obtained. There were no differences in the rate of pressure rise, nor in the end-systolic pressure-volume relations. According to these findings and the results of other authors, it is concluded that the rat is not very suitable for studying "alcoholic cardiomyopathy".