Incorporation of [1-carbon-11]palmitate in monkey brain using PET.

UNLABELLED: We determined regional incorporation coefficients (k*) of plasma [1-11C]palmitate into stable brain lipids of anesthetized monkeys with PET.
METHODS: Carbon-11-palmitate was injected intravenously in untreated animals and in animals pretreated with methyl palmoxirate (MEP), an inhibitor of beta-oxidation of palmitate in the brain and periphery. Plasma radioactivity was followed, and brain radioactivity was determined at various times using PET. A least-squares method was used to fit the data to an operational equation to obtain regional values of k* and of cerebral blood volume (Vb) in individual experiments.
RESULTS: MEP significantly decreased the integral of plasma [11C]CO2 following 11C-palmitate infusion. Mean values of k* in monkeys not given MEP were 4.9, 4.2, 4.9, 4.0 and 2.9 x 10(-5) ml/sec.g for the temporal, frontal, parietal and occipital cortices and white matter, respectively. With the exception of k* in white matter, which was increased by MEP, k* in the other brain regions was not significantly changed by MEP. The Vb ranged from 0.035 ml/g to 0.048 ml/g in gray matter regions and equaled 0.022 ml/g in white matter.
CONCLUSION: PET can be used to determine regional incorporation coefficients of 11C-palmitate into the primate brain in vivo. Combined with MEP, 11C-palmitate could be used with PET to examine regional brain phospholipid metabolism in humans in normal and pathological conditions.