THE USE OF RADIOACTIVE LYSINE IN STUDIES OF PROTEIN METABOLISM

Abstract

Racemic lysine labeled with C¹⁴ in the epsilon carbon position was fed to dogs. The distribution of C¹⁴ in blood and tissue fractions is recorded. In normal dogs sacrificed at 24 hours, approximately one-third of the C¹⁴ was found in the urine, one-third in expired air, and one-third in the body, mostly in protein, predomantly as lysine residues. The rate of C¹⁴ excretion as CO₂, hour by hour, paralleled closely the amount of non-protein C¹⁴ in the blood plasma.