AJP - Endocrinology and Metabolism, Vol 255, Issue 6 E871-E874, Copyright © 1988 by American Physiological Society
Effect of isotope infusion and sampling sites on glucose kinetics during a euglycemic clamp
F. Jahoor, S. Klein, H. Miyoshi and R. R. Wolfe
Metabolism Unit, Shriners Burns Institute, Galveston, Texas.
The importance of the location of isotope infusion and blood sampling on
calculating glucose kinetics was studied in five mongrel dogs in the basal
state and when glucose turnover was increased during a hyperinsulinemic
euglycemic clamp. [U-14C]glucose was infused into the pulmonary artery,
unlabeled glucose was infused into a femoral vein to maintain euglycemia,
and blood was sampled from the right atrium (AV mode) and the femoral
artery (VA mode). In the basal state there was no difference between the AV
or VA mode in plateau specific activity; hence, the calculated rate of
appearance of glucose was the same with either mode. During the euglycemic
clamp procedure, plateau specific activity of the AV mode was significantly
lower than that of the VA mode (P less than 0.05). The rate of appearance
of glucose calculated from the VA mode was almost identical to the rate of
infusion of unlabeled glucose (13.0 +/- 1.4 vs. 12.6 +/- 1.4 mg.kg-1.min-1,
respectively), but the rate of appearance of glucose calculated from the AV
mode was 12% greater. This study demonstrates that the calculation of
glucose kinetics is sensitive to differences in sampling site when the
turnover rate is high relative to the mass flow rate (cardiac output times
substrate concentration).
