Determination of in vitro protein synthesis of chick livers using GC-MS analysis of [H-2(5)]phenylalanine

The GC-MS-system consisting of the auto-sampler A200S (CE Instruments), the GC 8000 (Fisons Instruments) and the quadrupole mass spectrometer MD 800 ( Fisons Instruments) was calibrated for measurement of low enrichment of [H- 2(5)]phenylalanine in the range between 0.01 and 1.0 molar percent excess. For this purpose, phenylalanine was converted to phenylethylamine, derivati zed to the tertiary-butyldimethylsilyl (t-BDMS) phenylethylamine and peak a reas at m/z 183 and m/z 180 were recorded in the selected ion recording mod e under electron ionization conditions and subsequently used for isotope ra tio analysis. An in vitro study was performed in order to follow the time course of [H-2( 5)]phenylalanine incorporation into the protein fraction of liver homogenat es obtained from newly hatched chicks. The incorporation of the label over time increased in a non-linear related manner. Feeding of the breeder hen w ith a dietary fish oil concentration of 20gxkg(-1) depressed incorporation of the label in the liver protein fraction of chicks hatched from these hen s, and thus decreased protein synthesis, compared to livers obtained from h ens fed a diet containing fish oil at 10gxkg(-1). It can be concluded that the tested GC-MS-system is suitable for in vitro a nd in vivo experiments on studying protein synthesis using [2H5]phenylalani ne as tracer amino acid.