INHIBITORY EFFECTS OF RB+ ON THE RESPONSES TO LEVCROMAKALIM AND P1060IN THE ISOLATED HUMAN MYOMETRIUM

The mechanoinhibitory effects of two structurally dissimilar K+ channe l openers, levcromakalim and P1060, and verapamil were compared in str ips of human myometrium bathed in either K-PSS (normal Krebs solution) or Rb-PSS (K+ salts replaced by Rb+ equivalents). In Rb-PSS the effec ts of levcromakalim and P1060 on amplitude and frequency of spontaneou s contractions were inhibited by more than 20- and 138-fold, respectiv ely, whereas those of verapamil were unaltered. These results indicate that K+ channel openers possess Rb-sensitive and Rb-insensitive mecha noinhibitory actions on the human uterus, the former being more import ant in the effects of P1060 than levcromakalim.