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 (three days, 3 to 3.2 mg.'kg.) and alloxan diabetic dogs were given 2 gm.'kg. glucose (in 200 ml. water) containing 2.3 μCi.'gm. 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 minutes. The glucose absorption in alloxanized dogs showed an early peak with a subsequent decline. In all three types of dogs a single exponential function described the glucose absorption for t > 90 minutes with an asymptotic value of about 2 gm.'kg. In normal and glucocorticoid-treated dogs, the glucose load decreased the hepatic glucose output by 50 and 70 per cent, 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 two factors: (a) the glucose drink failed to suppress the hepatic glucose output, and (b) it increased the clearance rate of glucose (the sum of MCR and renal clearance) very little.