Effect of nifedipine in arterial vasculature of human placenta.
1. Nifedipine induced concentration-dependent relaxations in segments of human placental arteries precontracted with 40 mM K+. 2. Preincubation of segments with nifedipine induced concentration-dependent inhibition of contractions elicited by 40 mM K+ (IC50, 2.5 x 10(-9) M) and 10(-7) M 5-HT (5.9 x 10(-8) M). 3. The time-course of contractions elicited by K+ and 5-HT (responses not sustained) in the absence and in the presence of nifedipine was different. 4. Nifedipine inhibited Ca addition-evoked contractions in Ca-free medium containing 40 mM K+ or 10(-7) M 5-HT, mainly those obtained in depolarized segments. 5. These results indicate that these arteries are very sensitive to nifedipine and that the voltage-operated Ca channels are more affected by the Ca antagonist than receptor-operated ones.
Marín
J
J
Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
Reviriego
J
J
Fernandez-Alfonso
M S
MS
Guerra
P
P
D001158:Arteries / Q000187:drug effects; D015220:Calcium Channels / Q000187:drug effects; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology*; D010920:Placenta / Q000098:blood supply; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D012039:Regional Blood Flow / Q000187:drug effects; D012701:Serotonin / Q000494:pharmacology
D015220:Calcium Channels; D012701:Serotonin; D009543:Nifedipine; D011188:Potassium