Reincorporation of iodinated peptides in vivo and the comparative effectiveness of tungstic and trichloroacetic acids in peptide separation.

The absorption of 125I-bovine IgG after oral administration to young rats has been followed by gel filtration and quantitatively by TCA precipitation. The wide spectrum of protein derivatives crossing the gut wall have been utilised to compare the relative effectiveness of 10% TCA, and 1% tungstic acid, as reagents for the quantitative assessment of radioactive proteins and peptides. Radioactive iodide was the chief radioactive metabolite when 125I-labelled bovine IgG was fed to young rats, there was no significant incorporation of small radioactive metabolites into protein during a second exposure to the gut wall.