Effect of amino acid and glucose administration during post -exercise recovery on protein kinetics in dogs. Okamura, Koji, Tatsuya Doi, Koichiro Hamada, Masao Sakurai, Keitaro Matsumoto, Kiyoko Imaizumi, Yasuyuki Yoshioka, and Masashige Suzuki. Saga Research Institute, Otsuka Pharmaceutical Co., Ltd. Higashisefuri-son, Kanzaki-gun, Saga 842-01, Japan, Laboratory of Biochemistry of Exercise and Nutrition, Institute of Health and Sports Sciences, The University of Tsukuba, Tsukuba, Ibaraki 305, Japan
APStracts 4:0053E, 1997.
The aim of this study was to examine the effect of amino acid and glucose administration after exercise on skeletal muscle protein kinetics. Ten beagle dogs fitted with chronic catheters in the artery and the femoral vein ran on a treadmill for 150 min. A 2-h intraportal infusion of a solution containing amino acids and glucose was started either immediately after (Early infusion: E) or 2 h after (Late infusion: L) exercise. Each dog was subjected to both treatments in a randomized order. Skeletal muscle protein kinetics were estimated using arteriovenous differences of phenylalanine coupled with [2H5] phenylalanine dilution. During exercise, the net balance of phenylalanine across the hindlimb was negative, suggesting net protein catabolism in both groups (E: -11.3 [umlaut]u} 4.4 and L: -10.6 [umlaut]u} 5.6 nmol/kg/min). The balance became positive, suggesting net synthesis in E, by 15 min after the start of the nutrient infusion (4.3 [umlaut]u} 6.4 nmol/kg/min), while it remained negative for the first 120 min of L when saline was infused (-10.1 [umlaut]u} 3.6 nmol/kg/min). During the nutrient infusion periods of E (0 to 120 min) and L (120 to 240 min), net phenylalanine uptake by the hindlimb tended to be higher in E than in L and it was significantly higher for the last 60 min of each period (10.9 [umlaut]u} 6.6 vs 5.4 [umlaut]u} 2.3 nmol/kg/min. P=0.049). Protein synthesis during the nutrient infusion period was also significantly higher in E than in L (29.7 [umlaut]u} 9.6 vs. 22.8 [umlaut]u} 11.5 nmol/kg/min, P=0.028), while the rates of proteolysis were comparable in E and L (18.7 [umlaut]u} 5.7 vs 17.2 [umlaut]u} 13.1 nmol/kg/min). These results suggest that while post-exercise net skeletal muscle protein balance is normally negative without nutrient supplementation, provision of amino acids and glucose during this period promotes protein accretion. In addition, earlier nutrient administration may be more effective to increase skeletal muscle protein synthesis during recovery compared with a later administration. While the mechanisms for these effects are not entirely clear, increased insulin responsiveness earlier in the recovery period may be involved. 

Received 9 August 1996; accepted in final form 13 February 1997.
APS Manuscript Number E386-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 5 March 1997