Respiratory Metabolism of Excised Normal and Diabetic Tissue.

Abstract

Studies were made of excised kidney and muscle tissue of normal and depancreatized dogs, in order to answer the following questions:

(1) With normal animals what is the respiratory metabolism of these tissues when removed from the body?

(2) In excised diabetic tissue (a) is the power to oxidize carbohydrate lost? (b) is the power to split carbohydrate into lactic acid lost?

The main features of the technique were (1) the employment of the Barcroft-Warburg manometers in the study of micro-respiration, (2) the comparison of tissues of normal and diabetic animals, (3) parallel determinations of the metabolism of the tissues of the same animal, and (4) the development of a technique for obtaining relatively untraumatized mammalian muscle, by stripping the fasciculi lengthwise, instead of mincing.

The results are as follows:

(1) The figures for oxygen consumption of kidney and muscle were remarkably constant. For instance in normal muscle the extreme variations in 24 consecutive determinations were from 2.3 to 3.1 cu. mm. per dry mg. per hour. These correspond to values obtained in both tissues by the method of analyzing arterial and venous blood simultaneously in the intact organ. The respiratory quotients were all within physiological limits and indicated that various mixtures of foodstuffs were oxidized. In 11 triplicate determinations the highest figure was 0.911. This cannot be reconciled with the widespread idea that only carbohydrate can be oxidized by muscle.

(2a) The average respiratory quotients were as follows:

These figures show that isolated diabetic tissue can oxidize only a small amount of carbohydrate.

(2b) Diabetic tissue retains the power of splitting carbohydrate into lactic acid. Therefore it is not a failure to glycolize which depresses the oxidation of carbohydrate in diabetes.