RESUMO
A method was devised to measure the fractional rate of protein synthesis in fish using a stable isotope labelled tracer (ring-D5-phenylalanine) instead of radioactive phenylalanine. This modified flooding dose technique utilizes gas chromatography with mass spectrometry detection (GC-MS). The technique was validated by measuring the fractional rate of protein synthesis in the liver and white muscle of Arctic charr (Salvelinus alpinus) and then tested by comparing the fractional rate of protein synthesis of fed and starved Arctic charr. The modified technique met the assumptions of the flooding dose technique and was successfully used to detect alterations in the rate of protein synthesis in fed and starved fish. This modified technique allows for studies on protein metabolism to be carried out in situations where the use of radioactivity is difficult, if not impossible.