Effects of protocatechuic acid and propranolol on myocardial metabolism and infarct size in dogs with acute myocardial infarction

The distal portion of the left anterior descending coronary artery (LAD) or one of its diagonal branches was isolated for subsequent occlusion, in 17 open-chest mongrel dogs, weighing 16 + SD 3 kg. Blood samples were collected simultaneously from the femoral artery and the vein accompanying the artery chasen for occlusion and for examining the lactate and potassium balance. Before occlusion in regional vein the lactate and K+ in control (n= 7) were 2.4 + 0.9 mmol/L and 3.66 + 0.12 mmol/L. After the occlusion of LAD, the Jactate increased t0 6.3 + 1.1 mmol/L and K+ was 3.36+0.1 mmol/L. Lactate and K+ balance were -70 + 10 %, -12.0+ 0.05 % at 30 min. In PA (00 mg/kg iv), partial but significant improvement in above indices which reduced to -18 +8 % (lactate 4.11 + 1.3 mmol/L) and -3.5+0.08 % (K+ 2.92 + 0.19 mmol/L) respectively at 30 min. After iv Pro (0.5 mg/kg) lactate and K+ balance showed +17 + 7% (2.5 + 0.9 mmol/L) and + 5.1 + 0.06% (2.44+0.12 mmol/L). Both drugs improved SBP (systolic blood pressure) x HR (kPa . bpm) (indirectly represent action of myocardial oxygen consumption) in dogs. The myocardial infarct area was measured by nitroblue tetrazolium ( N-BT ) technique and histological examination at 24 h after LAD occlusion. PA and Pro exerted significant reduction of myocardial infarct area (MIA) by 6.3 + 1.5 %. 4.9 + 2% respectively, in control 18,6 + 1.4 % at 24 h after occlusion. These results indicate that PA significantly improves ischemic myocardium but its potency is less than Pro.