Preliminary evaluation of [1-C-11]octanoate as a PET tracer for studying cerebral ischemia: A PET study in rat and canine models of focal cerebral ischemia

Octanoate is taken up into the brain and is converted in astrocytes to glut amine through the TCA cycle after beta-oxidation. We speculate that [1-C-11 ]octanoate may be used as a tracer for astroglial functions and/or fatty ac id metabolism in the brain and may be useful for studying cerebral ischemia . In the present study we investigated brain distribution of [1-C-11]octano ate and compared it with cerebral blood flow (CBF) by using rat and canine models of middle cerebral artery (MCA) occlusion and a high resolution PET. In rats brain distribution of [O-15]H2O measured 1-2 h and 5-6 h after ins ult was compared with that of [1-C-11]octanoate measured 3-4 h after insult . Radioactivity ratios of lesioned to normal hemispheres determined with [O -15]H2O were lower than those determined with [1-C-11]octanoate. These resu lts were confirmed by a study on a canine model of MCA-occlusion. Twenty-fo ur hours after insult, CBF decreased in the MCA-territory of the occluded h emisphere, whereas normal or higher accumulation of [1-C-11]octanoate was o bserved in the ischemic regions. The uptake of [1-C-11]octanoate-derived ra dioactivity therefore increased relative to CBF in the ischemic regions, in dicating that [1-C-11]octanoate provides functional information different f rom CBF. In conclusion, we found that [1-C-11]octanoate is a potential radi opharmaceutical for studying the pathophysiology of cerebral ischemia.