A comparison of N-15 proline and C-13 leucine for monitoring protein biosynthesis in the skin

The tracers L N-15-proline and L(1-C-13)-leucine were used to explore the s ynthesis of skin proteins in vivo in rabbits. They orally received a single dose containing an equimolecular mixture of L(1-C-13)-leucine and L N-15-p roline. The changes in the amounts of these tracers in blood and skin were monitored for a total of 8 h. The data showed the appearance of the two tra cers in blood within 15 min and their clearance in 8 h. They were both rapi dly (15 min) incorporated into skin proteins, but more proline was incorpor ated than leucine. We therefore consider L N-15-proline to be a better trac er than L(1-C-13)-leucine for studying protein metabolism in the skin.