Coronary artery diameter increase induced by a phosphodiesterase 5 inhibitor, E4021, in conscious pigs

The effects of intravenous infusions of 1, 3 and 10 microg/kg/min of the phosphodiesterase 5 inhibitor, E4021, at 30-min intervals on coronary artery diameter were studied in 8 conscious pigs monitored with a pair of piezoelectric crystals. The highest dose increased the diameter by 2.9 +/-0.5% (P <0.01 vs vehicle) of the baseline diameter, with a significant decrease in mean pulmonary arterial pressure. However, there were no changes in mean aortic pressure and heart rate. Additionally, E4021 significantly prolonged the duration of the diameter increase induced by nitroglycerin. Thus, phosphodiesterase 5 inhibition causes coronary artery diameter increase and produces an amplifying effect with nitroglycerin.