Coronary vasodilation is caused by: September 2009

Ans. A: AdenosineThe close relationship between coronary blood flow and myocardial 02 consumption indicates that one or more of the products of metabolism cause coronary vasodilation. Factors suspected of playing this role include:02 lack and increased local concentrations of CO2H+,IC,Lactate,Prostaglandins,Adenine nucleotides, andAdenosine.Asphyxia, hypoxia, and intracoronary injections of cyanide all increase coronary blood flow 200-300% in denervated as well as intact heas, and the feature common to these three stimuli is hypoxia of the myocardial fibers. A similar increase in flow is produced in the area supplied by a coronary aery if the aery is occluded and then released. This reactive hyperemia is similar to that seen in the skin. Evidence suggests that in the hea it is due to release of adenosine.