Intense exercise stimulates albumin synthesis in the upright posture

We tested the hypothesis that an elevation in albumin synthetic rate contributes to increased plasma albumin content during exercise-induced hypervolemia. Albumin synthetic rate was measured in seven healthy subjects at 1-5 and 21-22 h after 72 min of intense (85% peak oxygen consumption rate) intermittent exercise and after 5 h recovery in either upright (Up) or supine (Sup) postures. Deuterated phenylalanine (d₅-Phe) was administrated by a primed-constant infusion method, and fractional synthetic rate (FSR) and absolute synthetic rate (ASR) of albumin were calculated from the enrichment of d₅-Phe in plasma albumin, determined by gas chromatography-mass spectrometry. FSR of albumin in up increased significantly (P < 0.05) from 4.9 ± 0.9%/day at control to 7.3 ± 0.9%/day at 22 h of recovery. ASR of albumin increased from 87.9 ± 17.0 to 141.1 ± 16.6 mg albumin·kg body wt^{- 1}·day^-1. In contrast, FSR and ASR of albumin were unchanged in Sup (3.9 ± 0.4 to 4.0 ± 1.4%/day and 74.2 ± 8.9 to 85.3 ± 23.9 mg albumin·kg body wt^-1·day^-1 at control and 22 h of recovery, respectively). Increased albumin synthesis after upright intense exercise contributes to the expansion of greater albumin content and its maintenance. We conclude that stimuli related to posture are critical in modulating the drive for albumin synthesis after intense exercise.