FIGURE 7.

Model to fit the plasma d₃- and d₆-α-T enrichments. Based on the shape of the enrichment curves from the oral and intravenous doses, we evaluated a model where the gastrointestinal (GI) tract converts the oral d₃-α-T into a finite pulse going into the liver—that is, at a constant rate for a period of time (following an initial delay). We assigned the kinetics of the 2 tracers to be identical in the plasma α-T pool (Q_P) and in the liver α-T pool (Q_L), which is the source for the plasma α-T (36). Remarkably, a very simple combined model for the 2 tracers with just 7 parameters (turnover rate constants of the pools Q_L and Q_P, the magnitudes of the 2 doses and pulse durations, and, for the oral dose, an initial delay) fitted the plasma d₆- and d₃-α-T enrichment data. GI box converts the bolus capsule into a finite pulse (with an initial delay) entering the liver pool. (μmoles) = plasma volume (L) multiplied by the plasma concentration of α-tocopherol (μM); . Model fits are shown in Table 6.