The effects of long-term starvation and acclimation temperature on glucose regulation and nitrogen anabolism in the frog, Rana pipiens—I. Winter animals

Abstract

1.1. Concentrations of serum glucose, serum amino acids and serum urea, as well as total excreted urea were measured in frogs, Rana pipiens—obtained in January and February—acclimated at 4, 20 and 25°C, during food deprivation lasting 25, 17 and 27 days, respectively.2.2. The concentration of glucose and amino acids in serum was maintained at 38·5, 38·2 and 44·5 mg%, and 30·0, 39·8 and 27·4 mM, respectively in frogs acclimated at 4, 20 and 25°C, respectively.3.3. The concentration of urea in serum was maintained at a constant level of 3·67 and 3·76 mM in 20 and 25°C acclimated frogs. Frogs acclimated at 4°C had variable to zero quantities of urea in their serum.4.4. The rates of urea excretion were determined and observed to be maintained at a constancy of 192·8 and 222·6 mμmoles/g per hr in 20 and 25°C accilimated frogs, but at a variable but decreasing rate in 4°C acclimated frogs.5.5. Regulation of the concentration of glucose and amino acids in serum was discussed with respect to hormonal influence upon standard metabolism.6.6. The advantages of a metabolic dependence upon glycogen rather than triglycerides in hibernating R. pipiens was discussed.7.7. Based on these observations, it is suggested that glucose derived from glycogen is the primary mobilizable metabolite in winter frogs.