ONE OR MORE SERUM FACTORS PROMOTE PEPTIDE UTILIZATION IN CULTURED ANIMAL-CELLS

We have shown previously that MACT-T and C2C12 cells utilize methionin e-containing di- to octapeptides as methionine sources for protein acc retion and cell proliferation in the presence of 60 mL/L desalted feta l bovine serum. In this study, serum factors that may regulate the use of peptides as amino acid sources in C2C12 and MAC-T cells were exami ned. The basal media contained methionine-free Dulbecco's modified Eag le's medium supplemented with 4.0 mL/L bovine serum lipids, 10 mL/L ch emically defined lipid concentrate, bovine insulin (1 mg/L), 30 mL/L l ow protein serum replacement (LPSR-1) or 60 mL/L desalted animal serum . Treatment media included basal media supplemented with no methionine , L-methionine, or one of the methionine-containing peptides. L-Methio nine promoted protein and DNA accretion (P < 0.05) in the presence of desalted animal sera, insulin or LPSR-1. Methionine-containing peptide s also promoted protein and DNA accretion (P < 0.05) in the presence o f desalted animal sera or LPSR-1, but not with insulin, except methion ylleucine. In a cell-free medium, fetal bovine serum hydrolyzed peptid es to varying degrees. We conclude that animal sera contain one or mor e factors that regulate utilization of peptides as amino acid sources for C2C12 and MAC-T cells.