[1-11C]octanoate as a PET tracer for studying ischemic stroke : Evaluation in a canine model of thromboembolic stroke with positron emission tomography

Octanoate is taken up by the brain and converted in astrocytes to glutamine through the TCA cycle after β-oxidation. Consequently, [111C]octanoate might serve as a useful positron emission tomography (PET) probe for studying cerebral oxidative metabolism and/or astroglial functions. The present study attempted to evaluate the utility of using [111C]octanoate as a PET tracer for imaging and evaluating the pathopysiology of ischemic stroke. We used a canine model of thromboembolic stroke. Five male beagle dogs were implanted with an indwelling catheter in the left internal carotid artery. A single autologous blood clot was injected into the left internal carotid artery through the catheter. The brain distribution of [111C]octanoate and cerebral blood flow (CBF) were determined 24 h after insult using a high resolution PET scanner. Post mortem brain regions unstained with 2, 3, 5-triphenyltetrazolium chloride (TTC) were defined as infarcts. In the region of an infarct, accumulation of [111C]octanoate decreased concurrently with CBF reduction. In contrast, normal accumulation of [111C]octanoate was observed in ischemic but vital regions, suggesting that an increased accumulation of [111C]octanoate relative to CBF takes place in these regions. In conclusion, [111C]octanoate accumulated in ischemic but vital retions, indicating that [111C]octanoate is potentially useful PET tracer for imaging and evaluating the pathophysiology of ischemic stroke.