The effect of vasoactive drugs on local coronary flow

Abstract

A method is described by which it is possible to study the selective effects of vasoactive drugs on the small vessels of the coronary circulation of the dog. We incorporated xenon-133 with different drugs and derived the flow/volume ratios from the rate of fall of radioactivity at the injection site. Ratios were consistently reduced by angiotensin (−37%), pitressin (−40%), and propranolol (−13%), and were increased by dipyridamole (+23%), nitroglycerine (+14%), isoproterenol (+30%), adrenaline (+30%), and noradrenaline (+25%), indicating that these agents have an effect on the small coronary vessels. Ratios were unaltered by phenylephrine and by combinations of propranolol with adrenaline or noradrenaline, suggesting that alpha receptor sites may be absent from the small vessel bed under study.