Comparison of Vasodilator Effects of DN-9693, a Selective Inhibitor of Cyclic AMP Phosphodiesterase, and Isobutylmethylxanthine, a Non-Selective One, in Dogs

The present experiments were performed in anesthetized dogs in order to determine if DN-9693. a new antiplatelet agent known to selectively inhibit cyclic AMP phosphodiesterase (PDE), and isobutylmethylxanthine (IBMX), which inhibits both cyclic AMP and GMP PDEs, have different cardiovascular actions. With intra-arterial administration into the left anterior descending coronary, femoral, cranial mesenteric and renal arterial beds perfused at constant pressure with autologous blood, both agents increased blood flow in a similar dose range. DN-9693 was longer-acting than IBMX. Both agents were nearly equi-effective in the femoral circulation, but DN-9693 was 1.5-2 times less effective than IBMX in the others. With intravenous administration, both agents were equi-effective in increasing the maximum rate of rise of left ventricular pressure, heart rate and myocardial oxygen consumption and in reducing mean blood pressure. However, DN-9693 was less effective in increasing coronary sinus outflow than IBMX. These results suggest the following: 1) Vasodilation in the somatic rather than the visceral circulation is important in reducing mean blood pressure. 2) Cyclic GMP may not be involved in the cardiac action of PDE-inhibitors. 3) Cyclic GMP may be involved in the vasodilator effect of PDE-inhibitors in the coronary, mesenteric and renal circulations but least involved in the femoral circulation.