Glycolysis activity in flight muscles of birds according to their physiological function. An experimental model in vitro to study aerobic and anaerobic glycolysis activity separately.

An experimental system in vitro is presented to assess the activity of the entire glycolysis in tissue extracts, which allows determining aerobic and anaerobic glycolysis activities separately. Glycolysis activity has been measured in pectoral and supracoracoideus muscles of the homing pigeon and the domestic fowl. These muscles support different aspects of flight in the two birds and are representative models of the two kinds of basic movements, endurance and sprint. The results obtained showed that in type I red fibers (pigeon pectoral), glucose produced a high glycolytic activity, while it was a poor substrate for type IIb white fibers (fowl pectoral and the two supracoracoideus). White fibers, however, attained its maximum glycolytic activity with phosphorylated glucose as substrate. These results demonstrated the validity of the experimental system as a method for assaying the two kinds of glycolytic activity in tissues, and supply new information about the biochemical and physiological features of these types of fibers.