[Ionic mechanism of the stimulatory effect of noradrenaline on smooth muscle cells of the pulmonary artery].
Noradrenaline (NA) in a concentration of 5 X 10(-6) M produces depolarization of smooth muscle cells of the rabbit pulmonary artery and reduction of membrane resistance followed by contraction and increased excitability of muscle cells. Experiments with repolarization of the membrane exposed to NA in normal and Ca-free Krebs solutions have shown that activation of the NA-induced contraction is mainly due to Ca++ entering the cells through NA-sensitive potential-dependent Ca-channels. The NA-induced depolarization results from an initial decrease of K-permeability of the membrane subsequent increase of the permeability of NA-sensitive potential-dependent channels for Na+ and/or Cl-, which provides further depolarization of the membrane. Depolarization ceases after becoming sufficient for activation of potential-dependent non-inactivated K-channels. Voltage clamp experiments have shown that the NA-induced increased excitability is related to a reduction of slow, particularly of fast component of outward current, whose early activation prevents the development of regenerative process of action potential generation under normal conditions.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability; D003470:Culture Media; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000502:physiology*; D011651:Pulmonary Artery / Q000502:physiology; D011817:Rabbits
D003470:Culture Media; D007473:Ion Channels; D002118:Calcium; D009638:Norepinephrine
Ionnyĭ mekhanizm vozbuzhdaiushchego deĭstviia noradrenalina na gladkomyshechnye kletki legochnoĭ arterii.