Influence of nutritional status on exertion-induced forearm amino acid metabolism in normal man

Normal volunteers were evaluated in the postabsorptive state, following 10 days of protein-calorie starvation, and during intravenous feeding ( ivf ) to determine the impact of nutritional status upon exertion-induced muscle amino acid metabolism. An isolated forearm model allowed an evaluation of recovery of metabolism following 1 min of submaximal isotonic exercise. Forearm blood flow returned to near basal levels within 15 min after exertion during postabsorptive and ivf conditions, but remained greater than or equal to 150% of basal at 1 hr after exercise during starvation. At 30 and 60 min after exercise, forearm plasma flux of total and essential amino acids were unchanged from basal in the postabsorptive state. However, the pattern of essential amino acid flux demonstrated a relative reduction in isoleucine and leucine efflux compared with basal, and this pattern persisted throughout 1 hr of recovery. During starvation, a significant (P less than 0.05) increase in total and essential amino acid efflux was observed throughout the recovery period. Starvation was also associated with significant increases in alanine and lysine efflux during recovery. Intravenous feeding was associated with a significant (P less than 0.05) uptake of essential amino acids with respect to basal levels at 30 min after exercise. At 60 min, there was a shift to total amino acid efflux but no change from basal flux for essential amino acids. During ivf , the pattern of essential amino acid uptake returned to basal within 1 hr after exertion.