THE VALIDITY OF RATES OF GLUCOSE APPEARANCE IN THE DOG CALCULATED BY THE METHOD OF SUCCESSIVE TRACER INJECTIONS: I. EFFECTS OF SURGICAL HEPATECTOMY, EVISCERATION, AND ORDER OF TRACER INJECTION

Abstract

The validity of the method of successive tracer injections has been tested in vivo. Changes in the rates of C¹²-glucose appearance, calculated at each time of injection of a trace amount of C¹⁴-glucose as tracer, were compared with the corresponding measured changes in rates of intravenously infused C¹²-glucose in five hepatectomized and two eviscerated dogs. Computer analysis of all data indicated that three of four large discrepancies between measured and tracer-calculated changes in the rate of C¹²-glucose appearance were associated with poor performance of experiments. Aside from these discrepancies, the method of successive tracer injections provided grouped absolute values for the changes in calculated rates of C¹²-glucose appearance in nine other comparisons which were, on the average, 6% higher than the corresponding changes in the measured rate of C¹²-glucose infusion (S.D. ± 9%). This degree of correspondence was not noticeably affected by the order of tracer injections. The data show some indications of C¹²-glucose production by the abdominal viscera following hepatectomy. Misrepresentation of tracer-calculated rates of appearance as "turnover rates" is criticized.