Phosphorylase and glycogen levels in skeletal muscle and liver of hibernating and nonhibernating bats

Abstract

Determinations of skeletal muscle and liver glycogen concentration and active a and total t phosphorylase activities were made in bats (Myotis lucifugus) hibernating at 3°–5° and 20 hours after arousal at room temperature. After arousal, liver glycogen was decreased by half and muscle glycogen was increased over twofold. Concomitantly, muscle phosphorylase a was increased, phosphorylase t was unchanged and the ratio a/t was increased. In the liver, phosphorylase a, t and the ratios were increased upon arousal (calculated per unit of wet weight and per mg N). Epinephrine treatment was ineffective in the torpid hibernating bats, but in aroused bats, it decreased muscle and liver glycogen but increased muscle phosphorylase activity ratios only slightly. Histamine was ineffective in the aroused bats. Stimulating aroused bats to fly for short periods consistently resulted in lower muscle glycogen levels and in no change in muscle phosphorylase activity ratios. It is concluded that a) at least part of the increased muscle glycogen in the aroused bats comes from the liver, b) the changes in glycogen levels and phosphorylase activity are in some manner related and c) liver phosphorylase changes upon arousal, unlike that in muscle phosphorylase, involves an increase in total enzyme potential.