[Mechanisms of activation of coronary vessel smooth muscle contraction].
Experiments have been performed with smooth muscle cells (SMC) of the circular strips from the bovine left descending anterior heart artery with a diameter of 2--2.5 mm. Use was made of the double sucrose gap method with simultaneous recording of electric and contractile activity of SMC. The cathode of polarizing current produced depolarization of SMC membrane (cathelectrotone). After depolarization of the membrane reached the threshold, the action potential (AP) was generated, followed by SMC contraction. The anode of polarizing current caused hyperpolarization of the membrane (anelectrotone) accompanied by relaxation of the strip. The degree of relaxation depended upon the initial muscle tone and the magnitude of anelectrotonic hyperpolarization. The voltage-current characteristics of SMC show that the muscle cell membrane of the coronary arteries possesses pronounced rectifying properties. An increase in the external potassium concentration up to 160 mM results in depolarization of the SMC membrane preceded by AP. These changes are accompanied by initial phasic and subsequent tonic contraction. The phasic component of the contraction is suggested to be evoked by AP and tonic component by stable potassium depolarization.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002417:Cattle; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology
D011188:Potassium
O mekhanizmakh aktivatsii sokrashcheniia gladkomyshechnykh kletok koronarnykh sosudov.