Differential effects of prostacyclin and iloprost in the isolated carotid artery of the guinea-pig

The effects on membrane potential of prostacyclin and iloprost were compare d in smooth muscle cells of the guinea pig carotid artery. Both prostacycli n and iloprost induced hyperpolarization of the smooth muscle cells. In the presence of (3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9-carbaz olepropanoic acid (Bay U3405), an antagonist of TP receptors, the response to iloprost was unaffected while that to prostacyclin was increased. Ilopro st-induced hyperpolarizations were abolished by glibenclamide, while those to prostacyclin were either not affected, or converted to either depolariza tion or to rhythmic electrical activity. The latter effects of prostacyclin were abolished by Bay U3405. After removal of the endothelium, iloprost an d prostacyclin produced hyperpolarizations similar to those observed in con trol blood vessels. However, in the presence of glibenclamide, prostacyclin produced only depolarizations inhibited by Bay U3405. These results sugges t that iloprost activates IP receptors and K-ATP channels in smooth muscle. In contrast, prostacyclin produces additional endothelium-dependent and -i ndependent effects via activation of TP receptors. (C) 2001 Elsevier Scienc e B.V. All rights reserved.