Effect of available glucose on glycogen synthase and phosphorylase of the rat tapeworm, Hymenolepis diminuta and the mouse bile duct tapeworm, Vampirolepis microstoma
The primary purpose of this study was to correlate the available glucose with the activities of glycogen synthase and phosphorylase in two species of tapeworms. One species, Hymenolepls dimlnuta, is located in the small intestine of a rat. The other species, Vampirolepis microstoma, is located in the mouse bile duct. Available glucose was altered by manipulation of the host diet. The tapeworms were recovered from hosts that had been either fed a_d_ lib., starved 24 hr, or starved 24 hr then refed for 1 hr immediately prior to worm recovery.
The proportion of glycogen synthase and phosphorylase in the active form was directly correlated with available glucose. In H. dimlnuta glycogen synthase was predominately in the inactive D^ form (> 90y6) in both the fed and fasted worms. When glucose from the diet was again available to fasted worms, D synthase was rapidly converted to the active I form (up to 90$). The tissue concentration of glucose almost tripled when fasted worms were refed 1 hr.
Phosphorylase in H. dimlnuta was predominately in the active a form (> 80
The experiments were repeated in_ vitro, by incubating fasted worms in glucose and then measuring glucose uptake and the activity of the enzymes. It was discovered that Krebs-Ringer-Tris buffer was not an adequate incubation medium for incubations lasting for more than a few hours. However, RPMI 1640 tissue culture medium was a satisfactory incubation medium for long-term (overnight) Incubations. If RPMI 1640 was the incubation medium, similar results were obtained with H. dimlnuta and V. microstoma. It is suggested that the differences between the two species, in_ vivo, could be attributed to V. microstoma having access to glucose In the host’s bile.