Estimation of glucose production during exercise with a one-compartment variable-volume model.
A variable-volume one-compartment model of glucose kinetics and step increases in the rate of tracer infusion were examined for estimation of endogenous glucose production (Ra) during moderate exercise in dogs. A primed infusion of D-[3-3H]glucose was left constant or increased 1.5-, 2-, 3-, 4-, or 5-fold at the onset of a 60-min period of exercise. Application of a regression method, in which Ra and the effective distribution volume were estimated over time, revealed dynamic changes in Ra that were not evident during the constant tracer infusion with a fixed-volume model. Application of the fixed-volume model to studies performed with a two- or three-fold step increase in tracer resulted in the lowest sum-of-squares difference from the regression method. Our results demonstrate that application of a variable-volume model can be achieved during exercise by enrichment of the plasma specific activity through step increases in the rate of tracer infusion and application of a regression method. Alternately, estimates of Ra with a fixed-volume model can be improved by enrichment of the plasma specific activity through a single step increase in the rate of tracer infusion. Our results suggest that when endogenous Ra is changing rapidly, such as at the onset of exercise, these methods will provide a more accurate estimate of Ra than the standard fixed-volume model and constant tracer infusion.
Finegood
D T
DT
Department of Medicine, University of Alberta, Edmonton, Canada.
Miles
P D
PD
Lickley
H L
HL
Vranic
M
M
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D003627:Data Interpretation, Statistical; D004285:Dogs; D005947:Glucose / Q000008:administration & dosage / Q000096:biosynthesis*; D007700:Kinetics; D008954:Models, Biological; D005082:Physical Exertion / Q000502:physiology*; D012044:Regression Analysis
D001786:Blood Glucose; D005947:Glucose