[Static and dynamic components of length-dependent regulation of contraction of the atrial and ventricular myocardium].
The influence of changes in length of the frog isolated atrium and ventriculus upon the isometric twitches was investigated. The length-tension relationship of the first contraction following the step of stretch was independent of the inotropic agents (Ca20+, adrenaline). The stretch to 0,35 induced the 5.04 +/- 051 fold increment of active tension in ventriculus and 1.75 +/- 0.12-fold increment of active tension in atrium. The length-tension relationship of the first contraction seems to depend on the degree of myofilaments overlapping A long-lasting transition-process occurred after step of deformation. The influence of inotropic agents upon the length tension relationship was shown for steady state contractions. An additional effect of activation by the length in normal solution was estimated for ventriculus as 22 +/- 5% and for atrium as 30 +/- 7%. The data suggest that the steady component-myofilament overlapping and dynamic component-calcium activations by the length change may participate in heterometric regulation of myocardial contractions.
D000818:Animals; D001696:Biomechanical Phenomena; D002118:Calcium / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D006325:Heart Atria; D006352:Heart Ventricles; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects; D011895:Rana ridibunda; D013314:Stress, Mechanical; D013328:Strophanthins / Q000494:pharmacology
D013328:Strophanthins; D002118:Calcium; D004837:Epinephrine
Staticheskiĭ i dinamicheskiĭ komponenty geterometricheskoĭ reguliatsii sokrashcheniĭ miokarda predserdiia i zheludochka.