PHENTOLAMINE AND STRUCTURALLY RELATED-COMPOUNDS SELECTIVELY ANTAGONIZE THE VASCULAR ACTIONS OF THE K CHANNEL OPENER, CROMAKALIM

Abstract

1. The effects of cromakalim, a novel vasodilator agent believed to open K+ channels, were studied in a range of large and small arteries in vitro. In dog isolated coronary artery, precontracted with U46619 (a thromboxane A2-mimetic), cromakalim caused concentration-dependent relaxation which could be inhibited by phentolamine (10-100 microM). 2. The ability of phentolamine to antagonize cromakalim was selective since it did not affect responses to a number of other vasodilators including isoprenaline, nitroprusside or nicorandil. 3. The effect of phentolamine was not related to its alpha-adrenoceptor blocking actions since other alpha-adrenoceptor antagonists (prazosin 10 microM, rauwolscin..