A comparison of 15N proline and 13C 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 synthesis 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-proline. 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 tracers in blood within 15 min and their clearance in 8 h. They were both rapidly (15 min) incorporated into skin proteins, but more proline was incorporated than leucine. We therefore consider L N-15-proline to be a better tracer than L(1-C-13)-leucine for studying protein metabolism in the skin.