Use of carbon-14-labelled arginine to measure the catabolic rate of serum and liver proteins and the extent of amino-acid recycling.

Abstract

THERE is evidence that in both man1 and rat2,3 protein deficiency causes a decrease in the catabolic rate of plasma albumin, which may plausibly be regarded as an adaptive reaction. To demonstrate this, it is necessary either to use a label which is not re-utilized, such as radio-iodine, or to reduce re-utilization to a minimum by injecting proteins that have been biosynthetically labelled in a donor animal. Tissue proteins cannot be studied by these methods, and therefore it is not known whether they react in the same way as plasma albumin to changes in dietary protein intake.