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

¹ Department of Biochemistry, University of Manitoba, Winnipeg, Manitoba, Canada

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.

Key Words: glycogen-C¹⁴ • C¹⁴O₂ • glucose-U-C¹⁴ • lactate-1-C¹⁴ • glycogen synthesis in vivo • glycogen synthesis in vitro

Submitted on September 28, 1964