Regional rates of cerebral protein synthesis measured with L-[1- 11C]leucine and PET in conscious, young adult men: Normal values, variability, and reproducibility

Abstract

We report regional rates of cerebral protein synthesis (rCPS) measured with the fully quantitative L-[1-11C]leucine positron emission tomography (PET) method. The method accounts for the fraction (λ) of unlabeled amino acids in the precursor pool for protein synthesis derived from arterial plasma; the remainder (1-λ) comes from tissue proteolysis. We determined rCPS and λ in 18 regions and whole brain in 10 healthy men (21 to 24 years). Subjects underwent two 90-min dynamic PET studies with arterial blood sampling at least 2 weeks apart. Rates of cerebral protein synthesis varied regionally and ranged from 0.97±0.70 to 2.25±0.20 nmol/g per min. Values of rCPS were in good agreement between the two PET studies. Mean differences in rCPS between studies ranged from 9% in cortical regions to 15% in white matter. The λ value was comparatively more uniform across regions, ranging from 0.63±0.03 to 0.79±0.02. Mean differences in λ between studies were 2% to 8%. Intersubject variability in rCPS was on average 6% in cortical areas, 9% in subcortical regions, and 12% in white matter; intersubject variability in λ was 2% to 8%. Our data indicate that in human subjects low variance and highly reproducible measures of rCPS can be made with the L-[1-11C]leucine PET method. © 2008 ISCBFM All rights reserved.