Glucose kinetics during oral glucose tolerance test in normal, methylprednisolone treated and alloxan diabetic dogs

Using 2[³H]glucose as tracer, glucose turnover was measured (primed constant rate infusion) on dogs with indwelling arterial and venous catheters. Normal, methylprednisolone (MP) treated (3 days, 3 to 3.2 mg/kg) and alloxan diabetic dogs were given 2 gm/kg glucose g/kg 200 ml water) containing 2.3 μCi/g of [¹⁴C]glucose (U) to drink. The rate of absorption of glucose was calculated from the course of the specific activity of [¹⁴C]glucose in the plasma. In normal and MP treated dogs, the cumulative absorption of glucose could be described as a linear function of time for t<120 min. The glucose absorption in alloxanized dogs showed an early peak with a subsequent decline. In all 3 types of dogs a single exponential function described the glucose absorption for t>90 min with an asymptotic value of about 2 g/kg. In normal and glucocorticoid treated dogs, the glucose load decreased the hepatic glucose output by 50 and 70% respectively. The metabolic clearance rate (MCR) of glucose was greatly increased in both groups. There was a log to log correlation between MCR and immunoreactive insulin in the plasma. In alloxan diabetes the low glucose tolerance was due to 2 factors: the glucose drink failed to suppress the hepatic glucose output, and it increased the clearance rate of glucose (the sum of MCR and renal clearance) very little.