Skin and muscle protein metabolism are regulated differently in
response to nutrition.
Zhang, Xiao-Jun, David L. Chinkes, David Doyle, Jr., and Robert R.
Wolfe.
Metabolism Unit, Shriners Burns Institute and Departments of
Surgery and Anesthesiology, The University of Texas Medical Branch,
Galveston, Texas 77550
APStracts 4:0275E, 1997.
We have measured skin and muscle protein kinetics and amino acid (AA)
transport in anesthetized rabbits during: (1) 64-h fast; (2) AA
infusion; (3) AA plus fat emulsion infusion; and (4) AA plus
hyperinsulinemia. L-[ring-13C6]phenylalanine was infused as the
tracer and the ear and hindlimb were used as arteriovenous units to
reflect skin and muscle protein kinetics, respectively. Results: Skin
protein net balance was not different from zero in all groups,
indicating a maintenance of protein mass. In contrast, the [mu]uscle
net balance differed over a range from -1.6 +/- 0.6 after fasting to
0.2 +/- 0.2 [mu]mol.100 g-1.h-1 during hyperinsulinemia. In the skin,
59 - 66% of intracellular free phenylalanine came from proteolysis
and phenylalanine availability from proteolysis was positively
correlated to the protein synthesis rate. In conclusion, normal skin
maintains its constant protein mass by efficient reutilization of AA
from proteolysis. In contrast to muscle, skin protein is relatively
insensitive to control by nutritional and hormonal factors. Because
of the metabolic differences, when limb models are used for muscle
protein metabolism, the potential contribution by limb skin should be
considered.
Received 2 June 1997; accepted in final form 9 December 1997.
APS Manuscript Number E256-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 7 January 1998