Biphasic contraction induced by ouabain in human umbilical arteries.
The effects of nifedipine on the contraction induced by ouabain were investigated in helically cut human umbilical arterial strips. Ouabain (10(-7)-10(-4) M) induced a rapid transient (early) contraction and a persistent slow (late) contraction. Both effects were dose-dependent. The early contractions were inhibited by nifedipine (5 x 10(-9) and 10(-7) M) and by Ca2+-free solution containing 0.2 mM EGTA but the late contractions were not altered by nifedipine. The results suggest that ouabain could facilitate the transmembrane Ca2+ entry through voltage-sensitive Ca2+ channels.
Sato
K
K
Second Department of Internal Medicine, Nagoya City University Medical School, Japan.
Aoki
K
K
D001692:Biological Transport / Q000187:drug effects; D015220:Calcium Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D005260:Female; D006801:Humans; D009119:Muscle Contraction; D009543:Nifedipine / Q000494:pharmacology; D010042:Ouabain / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D014469:Umbilical Arteries / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*
D015220:Calcium Channels; D010042:Ouabain; D011189:Potassium Chloride; D009543:Nifedipine