Metabolism of adipose tissue in vitro

Abstract

Adipose tissue phosphorylates glycogen to the Cori ester, and also synthesizes glycogen from glucose-l-phosphate. Eluates of young and old animals differ markedly in synthetic activity, eluates of embryonic fat tissue being most active. Phosphoglucomutase is found in Brown interscapular adipose tissue of rate but not in ordinary white adipose tissue. Adipose tissue contains amylase which, in vitro, converts glycogen into non-fermentable low polysaccharides (trisaccharides) and only in small part to glucose. Hunger-fat suspended in phosphate-Ringer under specified conditions showed an avg. O2 consumption of 37 [mu] 1./hr./0.3 g. of fresh tissue, with an avg. R.Q. of 0.64. Glycogen-fat obtained after recovery feeding had an avg. rate of O2 consumption of 53 [mu] l./hr. and an avg. R.Q. of 1.05. These increases were transient and tended to fall after 1-2 hr. Addition of glucose to hunger-fat increased the avg. R.Q. to 0.79, but glycogen or lactic acid did not affect the R.Q. Addition of pyruvic acid increased the respiration rate to 51 and the R.Q. to 1.25. In serum the O2 consumption and R.Q. of hunger-fat were 55 and 0.78 respectively. With added glucose, the corresponding avg. values were 65 and 1.15. Glycogen fat, in serum, produced an O2 consumption rate of 115 and a R.Q. of 1.27, which was maintained for many hrs. and even rose to 1.6. Only a small fraction of the glycogen lost during incubation in the Warburg expts. was accounted for by the O2 consumed, most of it was recovered as non-fermentable tri- or polysaccharide.