Studies on the effects of nitrendipine on oxytocin, angiotensin II and ergometrine-induced contraction of pregnant human myometrium in vitro.
The effects of nitrendipine, a Calcium channel antagonist, on stimulated contractions of 72 tissue strips of pregnant human myometrium was studied. The agonists used were oxytocin, angiotensin II (AII) and ergometrine maleate. The concentration: response curves for the contractile effects on these agonists on the myometrial tissue strips were initially established in three separate but identical experiments (n = 24 in each group) over a predetermined optimal concentration range of each of the agonists. Contractions were recorded isotonically against a fixed tension of 500mg using microtorque technique. The curves were then re-established, for each agonist, in the absence and in the presence of 10(-9)M nitrendipine. The agonists consistently contracted the myometrial tissues in a dose-dependent manner during the establishment of the initial curves. The overall initial EC50 for the oxytocin treatment group was 6.4 x 10(-10)M, while the corresponding EC50s for the AII, and ergometrine treatment groups were 5.9 x 10(-11) and 4.0 x 10(-8)M respectively. Nitrendipine significantly blunted the myometrial tissue response to oxytocin. The EC50 of the oxytocin control group was significantly different from similar group treated with nitrendipine. (9.0 x 10(-10)M for the control, as compared with 8.3 x 10(-7)M for the nitrendipine treatment group p less than or equal to 0.05). Nitrendipine did not significantly influence the myometrial tissue response to AII or ergometrine.(ABSTRACT TRUNCATED AT 250 WORDS)
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Broughton Pipkin
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D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004874:Ergonovine / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D009568:Nitrendipine / Q000008:administration & dosage / Q000494:pharmacology*; D010121:Oxytocin / Q000008:administration & dosage / Q000494:pharmacology*; D011247:Pregnancy / Q000187:drug effects*; D014590:Uterine Contraction / Q000187:drug effects*
D000804:Angiotensin II; D010121:Oxytocin; D009568:Nitrendipine; D004874:Ergonovine