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

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Abstract
The vasodilating effects of verapamil, nifedipine and nitroglycerin were studied in relation to plasma levels of 6-keto-prostaglandin(PG)F1.alpha., PGE1, PGF2.alpha. and thromboxane (TX) B2 in dogs. Verapamil, nifedipine and nitroglycerin decreased peripheral vascular resistance from 1.00 .+-. 0.07 mm Hg/ml per min (mean) to 0.83 .+-. 0.05, from 0.99 .+-. 0.06to 0.80 .+-. 0.05 and from 1.03 .+-. 0.04 to 0.91 .+-. 0.04, respectively. Peripheral blood flow did not change significantly. Verapamil administration significantly increased plasma levels of 6-keto-PGF1.alpha., PGE1 and PGF2.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-PGF1.alpha., PGE1, and PGF2.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 TXB2 level. Evidently the vasodilating action of verapamil was mediated in part by the PG system.