Glucose kinetics in non-steady states

A two-compartment model has been used to represent glucose tracer kinetics in the rabbit. Simulations were performed in which the model system was not in a steady state. The disturbances from the steady state included: input and output rates constant but not equal, rates varying linearly with time, rates varying sinusoidally with periods of 2 h and 4 min and rates varying at 1-min intervals in a random manner. Plasma glucose concentrations and 'true' mean glucose uptake rates, over the 2-h period, were calculated from the simulated data. Glucose uptake rates were also calculated from the simulated 'experimental' results using compartmental analysis and assuming the model was in a steady state. The errors caused by using compartmental analysis were found, in most cases, to be small. If doubtful experiments were to be discarded then the variation in plasma glucose concentration would be a very good guide.