[Ionic mechanism of the Woodwors staircase].
Analysis of single-chamber model of electromechanical coupling in the myocardial cell has shown that Woodwors staircase can be imitated in two cases: 1) stationary input current Ca2+ strongly exceeds the potential-dependent uptake of Ca2+ into the cell through the sarcolemma; 2) the action potential (AP) is shortened abruptly with an increase of the myocardium stimulation frequency. The experiments performed on a fragment of the frog heart ventricle supported the conclusions of the model. Blocking of Ca-channels with nifedipine (10(-6) g/mol) at the background of isotonic substitution of 70% of NaCl resulted in the development of "negative staircase" with an increase of stimulation rhythm. An abrupt shortening of AP after rest at joint action of adrenaline (10(-6) g/ml) and blocker of Ca-channels D-600 (10(-6) g/ml) was accompanied by Woodwors staircase.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008955:Models, Cardiovascular; D009543:Nifedipine / Q000494:pharmacology; D011896:Rana temporaria; D016276:Ventricular Function
D007473:Ion Channels; D005711:Gallopamil; D009543:Nifedipine; D002118:Calcium; D004837:Epinephrine
Ionnyĭ mekhanizm lestnitsy Vudvorsa.