QUANTITATIVE MEASUREMENT OF CEREBRAL PROTEIN-SYNTHESIS IN-VIVO - THEORY AND METHODOLOGICAL CONSIDERATIONS

The true rate of cerebral protein synthesis can be calculated from the ratio of labeled proteins to integrated arterial plasma amino acid sp ecific activity (SA) only when the fraction of amino acid precursor po ol dilution is known. In the following, current experimental designs o n the measurement of cerebral protein synthesis are discussed and comp ared to our own approach in which the determination of regional precur sor pool dilution by recycled unlabeled leucine is combined with the q uantitation of regional cerebral protein synthesis rates. For this pur pose, a constant arterial plasma leucine SA level is maintained for 45 min by programmed intravenous infusion which is sufficient for comple te equilibrium between tissue leucine pool SAs and plasma free leucine SA. In addition to the regional assessment of the precursor dilution factor, protein radioactivity can be determined in the same tissue sam ple or in parallel brain sections of the same animal by quantitative a utoradiography. It is then possible to calculate the actual rate of pr otein synthesis using the correct fraction of precursor pool dilution. This renders our approach particularly suitable for the quantitative measurement of regional CPS under pathological conditions. (C) 1997 El sevier Science B.V.