INHIBITORY EFFECTS OF RB+ ON THE RESPONSES TO LEVCROMAKALIM AND P1060 IN THE ISOLATED HUMAN MYOMETRIUM

The mechanoinhibitory effects of two structurally dissimilar K+ channel openers, levcromakalim and P1060, and verapamil were compared in strips of human myometrium bathed in either K-PSS (normal Krebs solution) or Rb-PSS (K+ salts replaced by Rb+ equivalents). In Rb-PSS the effects of levcromakalim and P1060 on amplitude and frequency of spontaneous contractions were inhibited by more than 20- and 138-fold, respectively, whereas those of verapamil were unaltered. These results indicate that K+ channel openers possess Rb-sensitive and Rb-insensitive mechanoinhibitory actions on the human uterus, the former being more important in the effects of P1060 than levcromakalim.