Calcium channels, potassium channels and membrane potential of smooth muscle cells of human allantochorial placental vessels.
The membrane potential (Um), the main factor of the excitation-contraction coupling, of human allantochorial placental vascular smooth muscle cells (VSMCs) has been previously shown to depend on voltage-sensitive K+ channels. These channels were blocked by high external K+. To characterize other channels which regulated Um, various constrictor or/and vasodilators and channel blockers were used. Serotonin depolarized VSMCs, in normal medium, but induced a more marked depolarization in VSMCs predepolarized by high external K+. This depolarization was inhibited by nifedipine, a blocker of voltage-gated Ca2+ channels. Acetylcholine, sodium nitroprusside (without effect on Um in normal medium), hyperpolarized the predepolarized-high K+ medium VSMCs. This hyperpolarization was inhibited after addition of charybotoxin (a blocker of Ca2+-activated K+ channels) or/and glibenclamide (a blocker of ATP-sensitive K+ channels). A similar effect was obtained with isoproterenol. These results indicated that membrane potential of human placental allantochorial VSMCs was regulated by voltage-gated, Ca2+- and ATP-sensitive K+ channels and by voltage-dependent Ca2+ channels.
Guiet-Bara
A
A
Laboratory of Physiopathology of Implantation and Development, University P.M. Curie, Paris, France.
Ibrahim
B
B
Leveteau
J
J
Bara
M
M
D000109:Acetylcholine / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000482:Allantois / Q000098:blood supply; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology*; D002823:Chorion / Q000098:blood supply; D006801:Humans; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010920:Placenta / Q000098:blood supply*; D015221:Potassium Channels / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology
D000318:Adrenergic beta-Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020030:Nitric Oxide Donors; D015221:Potassium Channels; D009599:Nitroprusside; D012701:Serotonin; D009543:Nifedipine; D007545:Isoproterenol; D000109:Acetylcholine