INFLUENCE OF PHENYLALANINE IN THE MEDIUM ON PROTEIN SYNTHESIS OF CHICKEN EMBRYO FIBROBLASTS

The influence of phenylalanine (Phe) in the medium on protein synthesis of chicken embryo fibroblasts (CEF) was examined. CEF was derived from 9-d-old embryos by trypsin-EDTA digestion. To examine the deficiency of Phe in the medium, CEF was cultured in Dulbecco's modified Eagle's medium (DMEM) with or without Phe. CEF was also cultured in Dulbecco's phosphate buffered saline (PBS ($Ca^{2+}$, $Mg^{2+}$)) with or without $400{\mu}m$ Phe in order to examine the effect of Phe supplementation. All media were supplemented with 10% (v/v) fetal calf serum. After incubation for 6, 30 and 54 h, protein synthesis was measured by the incorporation of L-[2, $6-^{3}H$] Phe into CEF for further 18 h. Protein synthesis of CEF cultured in DMEM was higher than that in PBS ($Ca^{2+}$, $Mg^{2+}$). High specific radioactivity of Phe due to the low concentration of Phe in the medium resulted in the apparent increase in protein synthesis of CEF. Protein synthesis cultured in PBS ($Ca^{2+}$, $Mg^{2+}$) with Phe did not increase during 72 h of cell culture.