Relation between pool size and catabolism of albumin in the mouse

¹ Civil Aeromedical Research Institute, Federal Aviation Agency, Oklahoma City, Oklahoma

The catabolism of I¹³¹-labeled human serum albumin was investigated in mice in which the total albumin pool was increased with injections of massive amounts of human or mouse albumin. Control mice received the tracer albumin and saline solution. Daily whole-body radioactivity measurements were made on each animal over a period of several albumin half-lives. Since the absolute rate of albumin catabolism (mg/hr) is estimated by the product of the fractional rate (fraction of albumin pool/hr) and the pool size (mg of albumin), an unchanged or increased fractional rate concomitant with an increased pool size indicates a greater absolute rate of catabolism. A small increase in the fractional rate of albumin catabolism, unrelated to an immune response, occurred in the albumin-loaded mice. By inference, the equilibrium level of albumin in the serum is determined, in part, by a variable absolute rate of breakdown and this rate of breakdown is related to the total albumin pool size. Renal and fecal excretion of injected protein was insignificant.

Note:
With the Assistance of J. K. Abbott, D. N. Faulkner and M. H. Friedberg