Influence of Dietary Protein Levels and Hydrocortisone Administration on the Branched-chain Amino Acid Transaminase Activity in Rat Tissues

Abstract

To determine whether the branched-chain amino acid transaminase (BATase) could be regulated by changes in dietary protein and glucocorticoid treatment, the activity of this enzyme was measured in tissues of 200-g rats receiving diets containing zero, 18 or 75% protein and in tissues of rats given hydrocortisone injections. It was found that BATase increased significantly in liver, kidney and muscle, but not in intestinal tissue of rats receiving 75% or zero per cent casein diets for 10-day periods, as compared with enzyme activities of tissues from rats given an 18% casein diet. Some increases in BATase were also noted in tissues of rats given an 18% casein diet when the animals were injected with hydrocortisone. After multiple doses of this hormone, BATase increased in liver and muscle, but not in kidney. All 3 branched-chain amino acids were transaminated at the same rate by BATase from liver, kidney and intestine, but the BATase from muscle transaminated leucine at a faster rate than either isoleucine or valine.