Abstract
It is the conclusion of Cruickshank 1 that the isolated heart derives its energy at least in part from the combustion of fat. This deduction is based on the negative evidence that combustion of other fuels will not account for the total metabolism. According to Visscher and Mulder 2 the total oxygen consumption of the heart-lung preparation cannot be accounted for on the basis of the carbohydrate loss from the tissue and blood in that system. They found that in some cases as much as 80% of the total metabolism is non-carbohydrate, presumably fat. Previous studies on fat burning by striated muscle are conflicting. Palazzolo 3 reported a decrease, while Winfield 4 found no change in the fat content of muscle as a result of activity.
In order to elucidate this question further measurements of the total fat content of the mammalian ventricular muscle were made in two series of cases. For the first series hearts were obtained directly from anesthetized dogs, and for the second ventricular muscle was taken after periods of work in the heart-lung preparation. The two series were run concurrently and there was no selection of the animals for the two groups. The ventricular muscle was ground and 20 gm. samples taken for extraction and analysis for total fats by the Bloor 5 technique. The heart-lung preparations were made by the usual method and no additions of any material were made to the blood during the course of the experiments.
Analyses were made on 63 hearts, of which 25 were worked for periods of from one to 6 hours, the average time being 3 hours.
The observed data are shown in Table 1. It will be seen that there is great overlapping of values in the two series, as would he expected from the normal variability in fat content.
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