The effects of vasodilators on the relaxation of guinea-pig aorta during acute recoil

Background: We have investigated the effects of various vasodilators on smooth muscle relaxation during acute recoil with guinea-pig aorta to find effective therapies to prevent acute recoil at percutaneous transluminal coronary angioplasty (PTCA). Methods: Muscle strips from guinea-pig aorta without endothelium were placed in a bath filled with modified Krebs solution. The strip was isotonically stretched with a tension of 9 mN for 1 min, and then isometric tension was measured until the tension reached a steady state. Various vasodilators were applied during isometric tension measurement. Results: When no drug was applied (control), isometric tension reached a steady state within 20 min. The steady state was approximately 10% lower (more relaxed) than the stretched level. When isosorbide dinitrate (ISDN, 1 mM) was applied during isometric measurement, 18.7±5.3% greater relaxation occurred than in control relaxation (P<0.05, n=5). When nicorandil (1 mM) was applied, the following relaxation was 18.6±5.7% greater than control (P<0.05, n=8). The simultaneous application of glibenclamide (1 mM) completely inhibited such additional relaxation by nicorandil. Application of nifedipine (10 μM) caused a 12.9±2.5% greater relaxation than control (P=0.066, n=4). The first metabolite of sarpogrelate (BP984, 10 μM) caused much greater relaxation than control (23.7±7.9%, P<0.05, n=6). Amlodipine (10 μM), phentolamine (10 μM), and sarpogrelate (10 μM) had no influence on the relaxation of the strip. Conclusions: ISDN, nicorandil and BP984 significantly increase relaxation of the muscle strips after stretching compared to the control. These vasodilators may reduce acute recoil of the smooth muscle after PTCA.