MEASUREMENT OF ALBUMIN SYNTHETIC RATE DURING RECOVERY FROM INTENSE EXERCISE

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We measured hepatic albumin synthesis during the recovery from an intense intermittent exercise protocol previously shown to expand plasma volume. Using a primed-constant infusion of a stable isotopic tracer of phenylalanine, hepatic fractional synthetic rate (FSR) and absolute synthetic rate (ASR) of albumin were determined from the enrichment of phenylalanine in albumin and in the free intravascular precursor pool. Albumin FSR and ASR were 6.39+0.48% day-1and 120 +9mg (kgBW)-1 day-1, respectively, at 3 to 6 hours recovery from exercise; the FSR and ASR on the time control study day were 5.94+0.47% day-1 and 104+9mg (kgBW) -1 day-1 respectively. The 6% and 16% increases (P<0.05) in FSR and ASR following exercise were associated with an elevated plasma albumin content at 5 and 6 hours recovery (P<0.05), an increased total protein content throughout recovery (P<0.05), and a negative free water clearance (P<0.05) at 2,3 and 6.5 hours of recovery when compared to baseline values; these variables were unchanged from their baselines on the time control study day. Increased albumin content and reduced free water clearance both contribute to a retention of fluid within the circulation after intense exercise. The measured increase in albumin synthesis did not account for the entire increase in albumin content during recovery from exercise. Although the measured increase in albumin synthesis did not account for the elevated plasma albumin content in the 6 hours following exercise, we concluded that it was elevated sufficiently to account for the increased albumin content measured (in a prior study) after 24 hours of recovery.