[Cationic regulation of myocardial contraction and relaxation when contraction frequency is increased].
During augmentation of frequency of contractions or Ca2+ perfusate concentration the velocity of isotonic relaxation increased much more than the velocity or amplitude of contraction. The phenomenon of predominant activation of relaxation ( PPAR ) was less prominent at decreased Ca2+ concentration acidosis (pH 6,85), under action of calmodulin inhibitor, trifluoperazine, or replacement of Ca2+ ions by Sr2+. Diminution of Na2+ concentration to 25 mM was followed by apparent signs of cellular Ca2+--overload and elimination of PPAR . The results coincide with the suggestion that PPAR is caused by activation of calmodulin-dependent Ca2+ removal from the myoplasma and myofibrils.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000502:physiology; D002147:Calmodulin / Q000502:physiology*; D006168:Guinea Pigs; D006339:Heart Rate; D006863:Hydrogen-Ion Concentration; D007537:Isometric Contraction; D009200:Myocardial Contraction; D010210:Papillary Muscles / Q000502:physiology; D012964:Sodium / Q000502:physiology*; D014268:Trifluoperazine / Q000494:pharmacology
D002147:Calmodulin; D014268:Trifluoperazine; D012964:Sodium; D000252:Calcium-Transporting ATPases; D002118:Calcium
Kationnaia reguliatsiia sokrashcheniia i rasslableniia miokarda pri uvelichenii chastoty sokrashcheniĭ.