The Effects of Dilazep and SG 75 on Cyclic Nucleotides in the Coronary Artery

We examined the effects of new long acting coronary vasodilators (dilazep and SG 75) on cyclic nucleotides in the coronary artery and the myocardium at the maximum coronary blood flow. The cyclic AMP concentrations in the anterior descending coronary artery after the injection of saline (control), SG 75 (0.2 mg/Kg), and dilazep (0.1 mg/Kg) were 229 +/- 20 pmole/Gm, 249 +/- 21 pmole/Gm, and 320 +/- 21 pmol/Gm, respectively. A significant increase above control values was found in the dilazep treated group (p less than 0.02). The cyclic GMP concentrations in the coronary artery after the injection of saline, SG 75, and dilazep were 35.6 +/- 4.4 pmole/Gm, 40.4 +/- 3.3 pmole/Gm, 35.3 +/- 3.2 pmole/Gm, respectively. There were no significant differences between them. The cyclic AMP and cyclic GMP concentrations in the left ventricular muscle did not significantly increase after the administration of dilazep and SG 75. Our findings showed that the mechanism of coronary vasodilating action of dilazep might be associated with an increased cyclic AMP in the coronary artery.