Fractional synthetic rate of skeletal muscle protein during testosterone infusion

Testosterone (T) administration is known to increase muscle anabolism. However, traditional injections may not be maximally effective in the burned patient due to increased lipogenesis and lipid storage. Therefore, the effects of T infusion on skeletal muscle protein synthesis were investigated in normal male volunteers. Three subjects received 30 mg of methyl-testosterone infusion or the carrier (Intralipid) over a five hour period. Subjects were studied in a randomized manner and were blinded to the treatment. Muscle biopsies of the vastus lateralis were taken at 2 and 5 h of infusion. Fractional synthetic rate (FSR) was calculated based on the precursor-product method. The average intracellular enrichment over the time of incorporation was used as the precursor, whereas the change in protein-bound enrichment of ring-d, -phenylalanine from 2 to 5 h of infusion was the product. There was a trend toward increased FSR during T infusion (0.0801 0.018 (SD) vs 0.048 ±0.018 %/hr). However, this increase railed to reach statistical significance by paired t-test (p = 0.10). Contrary to our previous finding with chronic T injections, acute administration of T may not be a potent stimulator of muscle protein synthesis.