Effects of peripheral vasodilation caused by verapamil, nifedipine, and nitroglycerin on plasma prostaglandins and thromboxane concentrations.

We investigated the vasodilating effects of verapamil, nifedipine, and nitroglycerin in relation to plasma levels of 6-keto-prostaglandin (PG)-F1 alpha, PG E1, PG F2 alpha, and thromboxane (TX) B2 in dogs. Verapamil, nifedipine, and nitroglycerin decreased peripheral vascular resistance from 1.00 +/- 0.07 mmHg/ml/min (mean +/- SE) to 0.83 +/- 0.05, from 0.99 +/- 0.06 to 0.80 +/- 0.05, and from 1.03 +/- 0.04 to 0.91 +/- 0.04, respectively. However, peripheral blood flow did not change significantly. Administration of verapamil significantly increased plasma levels of 6-keto-PG F1 alpha, PG E1, and PG F2 alpha from 150 +/- 31 pg/ml to 350 +/- 98, from 56 +/- 34 to 87 +/- 33, and from 127 +/- 35 to 238 +/- 61, respectively, while neither nifedipine nor nitroglycerin had any effect on plasma 6-keto-PG F1 alpha, PG E1, and PG F2 alpha. Indomethacin pretreatment reduced the effects of verapamil on peripheral vascular resistance and plasma PG concentration. None of these drugs caused a significant change in the plasma TX B2 level. The results suggest that the vasodilating action of verapamil was mediated in part by the prostaglandin system.