Branched-chain amino-acids and albumin synthesis. Study with hepatocytes of normal and stressed rats

To evaluate the incorporation of branched-chain amino-acids (BCAA) in de novo synthesised albumin, a series of experiments was performed with cultured hepatocytes from normal (Group 1) and stressed rats (groups 2 and 3). Stress was induced by keeping the rats immobilised in a cold room for 6–8 h and assessed by the presence of bleeding ulcers in the stomach. The cells were cultured in a commercial synthetic medium (Ham F-12) poor in BCAA (5.74% of total) increasing amounts of BCAA were added to plates in groups 1 and 2 and equivalent quantities of nitrogen in the form of glycine were added to plates in group 3. In group 1, the increase in BCAA concentration from 22.74–210.8 mg/ml was followed by an increase in the albumin synthesis rate from 0.4–0.95 ug/mg cell prot/h. In group 2, the rise in BCAA was followed by a far greater increase from 0.3–5 ug/mg cell prot/h (at least 6 times normal levels). In group 3, only 20% of the increase in albumin synthesis obtained in group 2 was observed. These results suggest that in stress the liver increases the use of BCAA for protein synthesis, but the increase of nitrogen in the culture medium respresents only a low percentage of this effect.