A study of the effects of propranolol and/or K 1366 on the distribution of Rb86 clearance in the canine heart under selective coronary hypotension.

Effects of beta-blockers o-[2-hydroxy-3-(tert.-butylamino)-propoxy]-benzonitrile (Kö 136 1366) and propranolol, on regional Rb86 clearance in the dog myocardium under selective coronary hypotension were investigated. Selective coronary hypotension of the left circumflex artery below 50 mmHg significantly decreased the Rb86 clearance and its I/O ratio of the involved myocardium. Kö 1366 and propranolol had a general trend to decrease the regional Rb86 clearance in the non-ischaemic region and to increase it in the ischaemic region when compared with that of the control group. Therefore, the gradient of regional Rb86 clearance between the non-ischaemic and ischaemic region may decrease. However, these changes were not statistically significant. Although both Kö 1366 and propranolol groups demonstrated similar haemodynamic changes, a reduction in heart rate was larger with propranolol infusion than with Kö 1366. On the contrary, a decreasing rate in systemic arterial blood pressure was marked with Kö 1366. Epicardial ECG ST elevation was reduced after propranolol infusion, not after saline or KO 1366 infusion.