Leucine affects the fibroblastic Vero cells stimulating the cell proliferation and modulating the proteolysis process

Branched-chain amino acids, especially leucine, exert regulatory influences on protein and carbohydrate metabolism, ribosome biogenesis and gene expression. This study investigated the effects of leucine in fibroblastic cells analysing viability, proliferation, morphology, proteolysis enzymes activities and protein turnover. After exposure to culture medium enriched with 25 or 50 microM leucine for 24, 48 and 72 h, Vero cells have no alterations on viability and morphology. Leucine-treated cells showed increase on alkaline phosphatase activity and proliferation. The protein synthesis was slightly increased, whereas the protein degradation showed a deep reduction after leucine incubation. The chymotrypsin-like, cathepsin B and H and calpain activities were decreased in leucine-treated cells. In conclusion, the proteolytic pathways and the total protein degradation were modulated by leucine in Vero cells. Our observations support the concept that Vero cells may represent a new model for protein turnover study.