Plasma Protein. IV. Results with Generally Labeled Plasma Protein. ∗

Abstract

Summary

It is possible to produce generally labeled plasma protein with very high specific activity in rats by feeding them suitable bacteria (Rhodospirillum rubrum) cultured in media containing labeled bicarbonate. These bacteria have protein in which all the amino acids present are labeled. The metabolism, in the recipient rats; of the C¹⁴ in the plasma protein from these donor animals (B) has been investigated and compared with that already described ( 1 , 2 , 7 ) for plasma protein labeled by feeding donor rats serine-β-C¹⁴ (A), with the following results: (1) The disappearance of the C¹⁴-labeled protein B from the circulation, following its intravenous injection, follows the same curve as that found when protein A was employed. (2) The appearance of C¹⁴O₂ in the respiratory gases is significantly less in these animals following the parenteral injection, but more following the oral administration than in recipients A. (3) As compared with A, the tissues of recipients B contain more C¹⁴-labeled protein no matter which route of administration is employed, and this is particularly true when the C¹⁴-labeled protein is given orally.