EFFECT OF AMINO-ACID AND GLUCOSE-ADMINISTRATION DURING POSTEXERCISE RECOVERY ON PROTEIN KINETICS IN DOGS

To examine the effect of the timing of amino acids (AA) and glucose (G ) administration after exercise on protein kinetics, ten dogs fitted w ith chronic catheters in the artery and the femoral vein ran on a trea dmill for 150 min. They were intraportally infused with a solution con taining AA and G either right after (E) or 2 h after (L) the exercise. The protein kinetics were estimated using the arteriovenous differenc e of phenylalanine (Phe) coupled with the [H-2(5)]Phe dilution method. The net balance of Phe across the hindlimb (HL) was negative after ex ercise. It became positive in E within 15 min after the start of the i nfusion, and it remained negative in L until the infusion was initiate d. The uptake of Phe by the HL during the second half of the infusion period was higher in E than in L (10.9 +/- 6.6 vs. 5.4 +/- 2.3 nmol.kg (-1).min(-1), P = 0.049). During the infusion, protein synthesis in th e HL was higher in E than in L (29.7 +/- 9.6 vs. 22.0 +/- 10.1 nmol.kg (-1).min(-1), P = 0.028), whereas proteolysis was comparable (18.7 +/- 5.7 vs. 16.5 +/- 11.1 nmol.kg(-1).min(-1)). These results suggest tha t the early provision of the nutrients after exercise more effectively enhances protein accretion than nutrients administered later.