Turnover Studies with Iodine-Labeled Gamma-Macroglo-Bulin and Albumin

Abstract

1. Turnover studies with purified cold agglutinins and other γ_1M-globulins labeled with radioactive iodine show that these proteins are degraded in the intravascular compartment or in some site in rapid distribution equilibrium with plasma.

2. Four of the γ_1M-globulins studied were degraded at a rate of about 8 per cent of the intravascular pool per day, while one γ_1M-globulin (cold agglutinin) was degraded at a rate of 18 per cent per day.

3. The transfer rate of γ_1M-globulins from the intra- to extravascular compartment was 9 to 16 Der cent of the intravascular pool per day, and the extravascular pools were 21 to 37 per cent of the total pool.

4. With labeled albumin the transfer rates from the intra- to extravascular compartment. were 35 to 72 per cent of the intra vascular pool per day.

5. The transfer rates for albumin, γ_ss globulin make it probable that the capillary permeability for these macromolecules is dependent on their molecular size.