INHIBITION OF CONTRACTIONS OF THE ISOLATED HUMAN MYOMETRIUM BY POTASSIUM CHANNEL OPENERS

OBJECTIVE: The aim was to investigate the properties of two potassium channel openers in human myometrium. STUDY DESIGN: The abilities of aprikalim and BRL 38227 to inhibit contractions produced by potassium chloride and oxytocin of myometrial strips from nonpregnant and pregnant women were studied. RESULTS: Aprikalim (1 and 10 mumol/L) and BRL 38227 (1 and 1 0 mumol/L) suppressed contractions induced by low (10 and 20 mmol/L) but not high (40 and 80 mmol/L) potassium chloride concentrations. Aprikalim and BRL 38227 were also potent relaxants of oxytocin (1 nmol/L)-induced contractions with rapid onset of action, of similar potency to each other, and reversible. Both compounds were significantly more potent against oxytocin (1 nmol/L)-induced contractions in myometrial strips from nonpregnant than from pregnant women. Aprikalim and BRL 38227, as relaxants of oxytocin-induced contractions, were antagonized by glibenclamide (1 mumol/L), a blocker of adenosine 5'-triphosphate-sensitive potassium channels. CONCLUSIONS: The results suggest that aprikalim and BRL 38227 relax the human myometrium by potassium channel opening, possibly at adenosine 5'-triphosphate-sensitive potassium channels. Compounds of this pharmacologic class are useful for investigating the physiologic functions of potassium channels in this tissue and could have a place in the treatment of dysmenorrhea and preterm labor.