Response of skeletal muscle protein synthesis to insulin in suckling pigs decreases with development

of skeletal muscle protein synthesis to insulin in suckling pigs decreases with development. Am. J. Physiol. 275 (Endocrinol. Metab. 38): E602–E609, 1998.—The elevated rate of muscle protein deposition in the neonate is largely due to an en-hanced stimulation of skeletal muscle protein synthesis by feeding. To examine the role of insulin in this response, hyperinsulinemic-euglycemic-amino acid clamps were per-formed in 7- and 26-day-old pigs. Pigs were infused with 0, 30, 100, or 1,000 ng·kg20.66 ·min21 of insulin to mimic the plasma insulin levels observed under fasted, fed, refed, and supra-physiological conditions, respectively. Whole body amino acid disposal was determined from the rate of infusion of an amino acid mixture necessary to maintain plasma essential amino acid concentrations near their basal fasting levels. A flooding dose of L-[4-3H]phenylalanine was used to measure skeleta