title: Studies on the effects of nitrendipine on oxytocin-, angiotensin II- and ergometrine-induced contraction of pregnant human myometrium in vitro.
abstract: Calcium channel blockers inhibit myometrial contractility by preventing the increase in intracellular free calcium which follows stimulation. They could thus be useful in treating premature labour. The effect of nitrendipine, a dihydropyridine calcium channel antagonist, on the contractile response of strips of pregnant human myometrium to oxytocin, angiotensin II (AII) and ergometrine has been examined. A total of 68 tissue strips were studied, with random allocation to treatment group. Initial concentration: response curves to one of the three agonists were determined; the concentration:response determinations were repeated in the presence or absence of nitrendipine at 10(-9)M. The initial EC50S for tissues exposed to oxytocin and AII were 8.2 X 10(-10)M and 3.4 X 10(-8)M respectively. The contractile response to both agonists was significantly blunted in the presence of nitrendipine (ANOVA; P less than 0.001 for both agents). This effect was greatest at high agonist concentrations. The initial EC50S for tissues exposed to ergometrine was 3.9 X 10(-8)M. Exposure to nitrendipine blunted the response (ANOVA; P less than 0.001), an effect most marked at low concentrations of ergometrine. The effect of nitrendipine on myometrial responses to the naturally occurring hormones oxytocin and AII supports suggestions of a role for it in inhibiting premature labour.
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital, Queen's Medical Centre, Nottingham.
authors.forename: C U
authors.initials: CU
authors.lastname: Odum
authors.forename: F
authors.initials: F
authors.lastname: Broughton Pipkin
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004874:Ergonovine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D009568:Nitrendipine / Q000494:pharmacology*; D010121:Oxytocin / Q000494:pharmacology*; D011247:Pregnancy; D011897:Random Allocation; D014590:Uterine Contraction / Q000187:drug effects*
chemical_list: D000804:Angiotensin II; D010121:Oxytocin; D009568:Nitrendipine; D004874:Ergonovine