An animal model for measurement of protein metabolism in the skin.

Abstract

A suitable in vivo approach with which to quantify skin protein metabolism has not been found, and consequently no information exists relating protein synthesis to protein breakdown in the fasted state. Stable isotope-labeled phenylalanine was infused into five fasted rabbits, and amino acid and protein kinetics were calculated from a three-compartment model with the rabbit ear used as an arteriovenous balance mode. Results were compared with the more traditional but limited direct incorporation technique to measure synthesis. The model-derived skin protein synthesis rate was 0.34%/hr +/- 0.04%/hr, which was almost identical to the value of 0.30%/hr +/- 0.01%/hr determined by the direct incorporation method. The model-derived skin protein breakdown rate was only slightly higher than the synthesis rate, meaning protein balance was generally maintained in the fasted state because of the efficient reuse of amino acids from protein breakdown. The newly described rabbit ear model is a reliable approach to the determination of the amino acid and protein kinetics in the skin in vivo. Efficient reuse of amino acids released from proteolysis explains the maintenance of skin integrity during brief fasting.