ACUTE STIMULATION OF ALBUMIN SYNTHESIS RATE WITH ORAL MEAL FEEDING IN HEALTHY-SUBJECTS MEASURED WITH [RING-H-2(5)]PHENYLALANINE

1. The short-term effect of oral feeding on albumin synthesis rate was investigated in 12 healthy volunteers using two meal regimens, Albumin synthesis was measured over 90 min after injection of a 'flooding' amount (43 mg/hg body weight) of phenylalanine enriched to 7.5, 10 or 15 atoms % with the stable isotope [ring-H-2(5)]phenylalanine. 2. In one set of subjects, consumption of five small hourly meals resulted in a consistent and significant increase (P<0.05) in albumin fractional synthesis rate from a mean (+/-SEM) fasting value of 5.8 (+/-0.4) %/day to 7.1 (+/-:0.4)%/day in the fed state. 3. A second study in which albumin synthesis was measured 30 min after consumption of a single larger meal was carried out in another set of volunteers, The fractional rate of albumin synthesis was again significantly elevated after feeding (P<0.05), rising from 7.1 (+/-0.4)%lday in the fasted state to 9.1 (+/-0.6) %/day in the fed state, In both studies, similar responses were observed in the absolute rate of albumin synthesis (mg day(-1) kg(-1)). 4. Albumin secretion time was significantly shorter (P<0.05) after feeding in both studies, suggesting that the acute stimulation in albumin synthesis observed after feeding may in part be mediated via a post-transcriptional mechanism. 5. The response of total liver protein synthesis to oral feeding was investigated in an animal model employing adult rats studied with a flooding amount of [2,6-H-3]phenylalanine. 6. The results indicated a stimulation of 20%, with no difference in the proportion of albumin synthesis relative to total liver synthesis, determined from the immunoprecipitation of albumin from the Liver.