Combined effects of hyperaminoacidemia and oxandrolone on skeletal muscle protein synthesis

We investigated whether the normal anabolic effects of acute hyperaminoacid emia were maintained after 5 days of oxandrolone (Oxandrin, Ox)-induced ana bolism. Five healthy men [22 +/- 3 (SD) yr] were studied before and after 5 days of oral Ox (15 mg/day). In each study, a 5-h basal period was followe d by a 3-h primed-continuous infusion of a commercial amino acid mixture (1 0% Travasol). Stable isotopic data from blood and muscle sampling were anal yzed using a three-compartment model to calculate muscle protein synthesis and breakdown. Model-derived muscle protein synthesis increased after amino acid infusion in both the control [basal control(BC) vs, control + amino a cids (C+AA); P < 0.001] and Ox study [basal Ox (BOx) vs. Ox + amino acids ( Ox + AA); P < 0.01], whereas protein breakdown was unchanged. Fractional sy nthetic rates of muscle protein increased 94% (BC vs. C+AA; P = 0.01) and 5 3% (BOx vs. Ox + AA; P < 0.01), respectively. We conclude that the normal a nabolic effects of acute hyperaminoacidemia are maintained in skeletal musc le undergoing oxandrolone-induced anabolism.