Effect of 2-nicotinamidethyl nitrate (SG 75) on coronary circulation

The effect of a new chemical agent, SG 75, on coronary blood flow of anesthetized dogs has been examined. Intravenous administrations of this agent in a dose of 10 microgram/Kg or over caused a significant increase in blood flow of non-constricted coronary artery. Percent increases in flow were 40 (10 microgram/Kg), 95 (50 microgram/Kg), 145 (100 microgram/Kg), and 195 (250 microgram/Kg). The increases were significantly larger than those caused by the same doses of diltiazem, verapamil, nitroglycerin, isosolbide dinitrate, and papaverine. The durations of the increase in flow were 12 (10 microgram/Kg), 23 (50 microgram/Kg), 28 (100 microgram/Kg), and 46 min (250 microgram/Kg), and they were longer than those caused by diltiazem and verapamil. A slight reduction in left ventricular tension and an increase in aortic blood flow were also observed following the administrations of SG 75 in a dose of over 50 microgram/Kg. A decrease in heart rate was produced with a dose of over 500 microgram/Kg. However, PQ interval of electrocardiogram became shorter. Intravenous administrations of SG 75 in doses of 50 and 150 microgram/Kg caused an increase in blood flow of the constricted coronary artery, while nitroglycerin (10 and 30 microgram/Kg) and nifedipine (1 and 3 microgram/Kg) reduced it. The results indicate that SG 75 is a potent and long-acting coronary vasodilating agent and it causes an increase in blood flow of constricted as well as non-constricted coronary artery.