SAA Kinetics in Animals

Abstract

Kinetic models have been established for the study of plasma proteins in which tracer quantities of radiolabelled proteins are administered intravascularly to animals and disappearance of radioactivity from the plasma compartment is monitored. Two conditions must be met. First, it is essential that the tracer be distributed and metabolized identically to the tracee. Secondly, the system must be in dymamic equilibrium, i.e., plasma concentrations must not fluctuate during the course of the study. If these criteria are met, one can plot a disappearance curve of radioactivity remaining in the plasma versus time on a log-linear scale. Slopes and intercepts extrapolated from the curve are then used to calculate half-life and fractional catabolic rate. If one also knows the plasma concentration of the protein of interest, it is possible to calculate synthesis rate. The total plasma mass of the protein can be determined from the initial specific activity (usually measured 5–10 minutes after infusion of tracer) and the dose of tracer (1).