Activity of the Vesicular Calcium Pump in the Spontaneously Failing Heart-Lung Preparation

Abstract

The in vitro calcium uptake activity has been examined in fragments of sarcoplasmic reticulum, i.e. vesicles, obtained from hearts spontaneously failing in the canine heart-lung preparation. The rate of uptake was found to be less than that observed for vesicles from control hearts. If the vesicles were prepared from a failed heart that had been treated in vivo with ouabain, then the rate of calcium uptake was normal. In vitro additions of ouabain increased the rate of calcium uptake only with vesicles prepared from failing hearts. This effect of ouabain on calcium uptake by vesicles appears, therefore, to be specific for the defect causing depression of calcium uptake. No evidence could be found that the depression of calcium uptake is due to uncoupling of the pump adenosine triphosphatase. Calcium uptake and adenosine triphosphatase activity were found to be proportionately depressed in the failing heart and proportionately restored by ouabain.