Regional rates of cerebral protein synthesis measured with L-[1-11C]leucine and PET in conscious, young adult men: normal values, variability, and reproducibility.
We report regional rates of cerebral protein synthesis (rCPS) measured with the fully quantitative L-[1-(11)C]leucine positron emission tomography (PET) method. The method accounts for the fraction (lambda) of unlabeled amino acids in the precursor pool for protein synthesis derived from arterial plasma; the remainder (1-lambda) comes from tissue proteolysis. We determined rCPS and lambda 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 lambda value was comparatively more uniform across regions, ranging from 0.63+/-0.03 to 0.79+/-0.02. Mean differences in lambda 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 lambda 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-(11)C]leucine PET method.
Bishu
Shrinivas
S
Section on Neuroadaptation & Protein Metabolism, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-1298, USA. bishus@mail.nih.gov
Schmidt
Kathleen C
KC
Burlin
Thomas
T
Channing
Michael
M
Conant
Shielah
S
Huang
Tianjiang
T
Liu
Zhong-hua
ZH
Qin
Mei
M
Unterman
Aaron
A
Xia
Zengyan
Z
Zametkin
Alan
A
Herscovitch
Peter
P
Smith
Carolyn B
CB
D000328:Adult; D002250:Carbon Radioisotopes / Q000008:administration & dosage / Q000378:metabolism*; D002540:Cerebral Cortex / Q000000981:diagnostic imaging / Q000378:metabolism*; D003243:Consciousness / Q000502:physiology*; D006801:Humans; D007930:Leucine / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D049268:Positron-Emission Tomography / Q000379:methods; D014176:Protein Biosynthesis / Q000502:physiology*; D015203:Reproducibility of Results; D013997:Time Factors
D002250:Carbon Radioisotopes; D007930:Leucine