The method of successive measured injections of tracer using uniformly labeled C-14-glucose as tracer was applied to determine the pool size, apparent distribution space and the rates of endogenous glucose production and utilization in the fasting state and at twenty to 110 minutes after the intravenous injection of a 0.3 gm./kg. glucose load in six nondiabetic and sixteen diabetic subjects.
The amount of intermixing glucose (“pool”) and the endogenous glucose production in the fasting state were higher in diabetics than in normals. The rate of glucose production decreased after the intravenous injection of the glucose in normals and nonketotic diabetics, but not in three out of four ketotic diabetics.
The average rate of glucose utilization in the fasting state was found to be slightly higher in diabetics than in normals, but it increased to a lesser extent following the injection of glucose. This smaller increase and larger glucose pool are the main causes of decreased glucose tolerance in diabetics.
The exponential slope of the concentration of glucose in the plasma after an intravenous injection of glucose (usually referred to as ‘K’) was not found to be correlated significantly with the rate of glucose utilization.