Na+/Ca2+ exchange mediation in the ouabain-induced contraction in human placental vessels.
1. Ouabain induced concentration-dependent contractions in segments of human placental arteries and veins, which were practically abolished in a Ca(2+)-free medium and not modified by the calcium antagonist nifedipine or the calcium agonist Bay K 8644. 2. Ouabain (10(-4) M) elicited a time-dependent enhancement of the 45Ca2+ uptake, which remained equal in presence of nifedipine or Bay K 8644. 3. The Na+/Ca2+ exchange blocker amiloride reduced both the contractions and the 45Ca2+ uptake induced by ouabain, whereas the Na ionophore monensin produced a parallel shift to the left of the concentration-response curve to ouabain. 4. These results suggest that ouabain-induced contractions in these vessels are dependent on the extracellular Ca2+, which mainly enters into the cell through the Na+/Ca2+ exchange system.
Fernández-Alfonso
M S
MS
Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma, Madrid, Spain.
Sánchez-Ferrer
C F
CF
Hernández
M C
MC
Marín
J
J
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D001158:Arteries / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008985:Monensin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology*; D010920:Placenta / Q000098:blood supply*; D012039:Regional Blood Flow / Q000187:drug effects; D012964:Sodium / Q000378:metabolism*; D014680:Veins / Q000187:drug effects
D002132:Calcium Radioisotopes; D010042:Ouabain; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000584:Amiloride; D008985:Monensin; D012964:Sodium; D009543:Nifedipine; D002118:Calcium