ALTERED GLUCOSE 1,6-BISPHOSPHATE AND FRUCTOSE 2,6-BIPHOSPHATE LEVELS IN LOW-FREQUENCY STIMULATED RABBIT FAST-TWITCH MUSCLE

Glucose 1,6-bisphosphate (Glc-1,6-P2) and fructose 2,6-bisphospate (Fru-2,6-P2) concentrations display pronounced increases in rabbit fast-twitch muscle during chronic low-frequency stimulation. These increases are first seen after stimulation periods exceeding 3 h and reach maxima after 12 24 h of stimulation (approximately 3-fold for Glc-1,6-P2 and 5-fold for Fru-2,6-P2). Both metabolites regress to normal values after stimulation periods longer than 4 days. The fact that their increases coincide with the replenishment of glycogen after its initial depletion, could point to a role of Glc-1,6-P2 and Fru-2,6-P2 in glycogen metabolism.