Glycogen and CO2 production from glucose and lactate by red and white skeletal muscle

Abstract

Diaphragm and external oblique muscle of the abdomen were identified histochemically as red and white muscles, respectively, in the rat. Administration of glucose orally to fasted rats 3 hr before sacrifice increased the glycogen in the red but not in the white muscle. Paired red and white muscles were incubated 2 hr in oxygen at 29 C in Krebs-Ringer phosphate medium at pH 74 containing 11 mm glucose and 40 mm dl-lactate. Glycogen increased in all the samples except in the red muscle specimens with high initial glycogen levels. The glycogen change and glucose-U-C14 incorporation into glycogen were both inversely related to the initial glycogen and were both greater in red than in white muscle. These differences between the muscles were suppressed by increasing the oral glucose dose. C14O2 production from glucose-U-C14 and lactate-1-C14 was greater in red than in white muscle.