[Changes in protein synthesis in the liver and small intestine of rats after feeding]

Rats trained on fast food intake received a combined intravenous injection of [14C]valine and unlabelled valine before and 1, 2, 4 and 6 h after food intake, respectively. The rate of protein synthesis was calculated basing on the average specific radioactivity of free valine in blood plasma and in the analyzed tissues during the 10 min incorporations period and on the specific radioactivity of protein bound valine in the tissues at the end of incorporation time. Before food intake the fractional rate of protein synthesis (ks) in liver was 55-67% per day and increased 1 to 4 h after food ingestion to 80-120% per day. ks in small intestine before food intake amounted to 78-109% per day and no specific changes were observed in time course. The synthesized amount of protein in liver and small intestine (related to 100 g body weight) was found to be 14-19 mg/h before food ingestion. This value increased postprandially in the liver to 25-32 mg/h and decreased towards the end of the testing period to 20-25 mg/h. The stimulation of the rate of protein synthesis in liver and perhaps in other organs may be part of a mechanism delaying the inflow of amino acids into tissues with lower turnover rates.