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.