A Further Contribution to the Derivation of Factors for Computing the Gaseous Exchange and the Heat Production in the Metabolism of Proteins

Publisher Website
Google Scholar
Abstract
Balances of nitrogen, carbon and energy were determined with six albino rats receiving first a mixed diet for maintenance, as the basal diet, and then the same diet supplemented, in different periods, with each of the three different proteins, namely, heart muscle, casein and gelatin in quantities of 1.5 gm. and 3.0 gm. each. The metabolizability of the proteins was determined from a comparison of the basal diet with each of the supplemented diets. Of the total calories of the proteins ingested at the two levels the following average percentages were metabolized: heart muscle, 86.61%; casein, 82.14%; gelatin, 81.06%. The following factors were determined for computing the respiratory exchange and the heat production in the metabolism of the different proteins, all values being expressed per gram of urinary nitrogen: for heart muscle, 5.96 liters of respiratory O2, 4.75 liters of CO2 and 26.71 calories; for casein, 6.76 liters of O2, 5.58 liters of CO2 and 31.15 calories; for gelatin, 5.05 liters of O2, 4.22 liters of CO2 and 23.44 calories. The factors for casein are in close agreement with those previously determined by Kriss and Miller. The factors for heart muscle agree very closely with those reported by Loewy and Oppenheimer for meat.