THE RELATIONSHIP BETWEEN ATRIAL CONTRACTIONS AND THE EFFECT OF OUABAIN ON CONTRACTILE STRENGTH AND CALCIUM EXCHANGE IN RABBIT ATRIA.

摘要: The effects of 10 -6 M ouabain on contractile strength and calcium exchange in isolated rabbit left atria were investigated as a function the number contractions during 5-minute exposure to Ca 45 . As beats was increased control atria, specific activity tissue reach maximum value between 300 500 beats. This is consistent with existence contraction-dependent "pool" calcium. size this estimated being order 10-6 10-7 moles Ca/kg wet tissue. action associated marked increase value. result cannot be explained simply basis an rate but suggests that has made more available for contraction, perhaps by increasing magnitude pool. It demonstrated early phase toxicity, there additional 2-fold activity. may therefore considered proceed two phases. positive inotropic effect exchangeable Progression toxicity further exchange, which reflection slight uptake per beat presence absence presented. After had occurred, from 5.43 14.31 picomoles/cm 2 / beat, nearly 3-fold increase. question whether alters thereby affects or altered changes force produced some other ouabain, considered. data presented are interpreted indicating primarily force.