Activity of enzymes regulating glycogen metabolism in perfused muscle-cuticle sections of Ascaris suum (Nematoda)

A new perfusion system has been developed in which muscle-cuticle sections of Ascaris suum were perfused, enabling study of enzymes in vitro. Using this technique the activity of the regulatory enzymes glycogen synthase and glycogen phosphorylase was determined, and the level of glycogen in the muscle was assessed. During starvation, 98% of glycogen synthase was in the inactive D-form, and 80% of the glycogen phosphorylase activity was in the active a-form. When the ascarid muscle section was perfused with 27 mM glucose, 13.1% of the glycogen synthase was in the active I-form, whereas phosphorylase a-levels dropped to 46% and glycogen was synthesized at a linear rate of 12 mg/g/hr or 1.23 µmoles/min/g muscle-cuticle. ATP levels (3.71 ± 0.32 mM) remained unchanged over a 4-hr perfusion period with an adenylate energy charge of 0.82. Fructose supported glycogen synthesis, though not as well as glucose. Galactose, mannose, and trehalose did not support glycogen synthesis. The new perfusion system should be useful in future, similar studies on Ascaris.