Use of Carbon-14-labelled Arginine to measure Catabolic Rates of Proteins and the Recycling of Amino-acids

Abstract

Stephen and Waterlow¹ have described the use of carbon-14-labelled arginine to measure the catabolic rate of serum and liver proteins in normal rats and rats fed on a diet deficient in protein. Differential assay of the isotope activity in the C(1) and C(6) atoms of arginine shows a variation in values between the true and apparent half lives of the proteins. The technique is of value for studying the recycling of amino-acids and for measuring catabolic rates. The authors have made the observations that the decrease in protein catabolic rate and the increased recycling of amino-acids which occur in the rats fed a diet free of protein may constitute an adaptive phenomenon for the conservation of protein in the deficient animal.