Glucoregulation in dogs treated with methyl-prednisolone.

In nonanesthetized dogs treated with 3 mg/kg . d methyl-prednisolone (MP) for four days the infusion of phlorizin decreases plasma glucose only transiently. The basal level is restored by an increase in hepatic glucose production. The concentration of plasma glucagon (IRG) is raised only about 26%, compared to the increase of 150% observed previously in untreated dogs. In insulin-induced hypoglycemia, hepatic glucose production increases and both the concentrations of epinephrine and IRG in the plasma are elevated significantly. Recovery from hypoglycemia after the cessation of the infusion is significantly faster than observed previously in normal dogs. The following conclusions were reached: In MP-treated dogs during the infusion of phlorizin (in nonhypoglycemic glucoregulation) normoglycemia is restored faster, and by a much smaller increment in plasma glucagon concentration than previously observed in normal dogs. Regulation in overt hypoglycemia too operates more efficiently. In nonhypoglycemic glucoregulation a small change in plasma glucose concentration appears to be the primary stimulus that releases glucagon to the extent necessary to achieve the appropriate increase in hepatic glucose production in a given endocrine milieu.