Chapter 6 – Tracer Experiment Design for Metabolic Fluxes Estimation in Steady and Nonsteady State

Publisher Summary Understanding the functioning of a metabolic system requires the quantitation of processes that are not directly measurable because they take place in the nonaccessible portion of the system. Among these processes, production and utilisation of substrates and secretion of hormones are of utmost importance for the investigator. The aim of this chapter is to describe tracer techniques for the quantitation of such fluxes under steady- and nonsteady-state conditions. Although the treatment is fairly general, we will use the glucose system as a prototype. In this chapter, focus has been placed on tracer experiment design strategies needed to quantitate production and utilisation fluxes of a substance under both steady- and nonsteady-state conditions. The steady-state problem is easy to tackle, and it has been emphasised that, under steady-state conditions, approaches to a rapid attainment of the tracer steady state require attention in selecting the ratio between the priming dose and the constant infusion. The nonsteady-state situation is far more complex, and the adoption of “intelligent” infusion strategies becomes a must.