RELAXATION OF HUMAN UTERINE ARTERY IN RESPONSE TO PINACIDIL - PREDOMINANT ROLE FOR ATP-DEPENDENT POTASSIUM CHANNELS

The effect of pinacidil on human isolated uterine artery rings was inv estigated. Pinacidil (10 nM-300 mu M) induced a concentration-dependen t relaxation of the precontracted arterial segments (pD(2): 6.26; maxi mal response: 98.5 %). Apamin (1 mu M) and tetraethylammonium (6 mM) h ad no effects on the pinacidil-evoked relaxation, while 4-aminopyridin e (0.1-6 mM) and glibenclamide (1-10 mu M) competitively antagonized t he response to pinacidil. The dissociation constants for 4-aminopyridi ne and glibenclamide were 240 mu M and 0.40 mu M, respectively. It is concluded that, in human uterine arteries, pinacidil induces relaxatio n. On the basis of differential antagonist affinities, we suggest that pinacidil produces a relaxation of this blood vessel through activati on of glibenclamide-sensitive, ATP-dependent potassium channels.