Figure 4.
Model examining effect of decreasing pool size on labeling kinetics. A simple linear system is modeled in which a labeled substrate (S) is introduced and is converted into a product (P) via two intermediates, A and B. The fractional enrichment of label in B is estimated by numerical iteration of mass balance differential equations. At steady state the influx into and efflux from pool B are given arbitrary values of 10 (JSA = 10, JAB = 10, JBP = 10). Several scenarios are examined that all lead to the same rate of decrease of pool B while the upstream JSA flux is constant: case 1 (JSA = 10, JAB = 8, JBP = 10), case 2 (JSA = 10, JAB = 10, JBP = 12), case 3 (JSA = 10, JAB = 12, JBP = 14), and case 4 (JSA = 10, JAB = 2, JBP = 4).