Estimation of oxygen metabolism in a rat model of permanent ischemia using positron emission tomography with injectable 15O-O2

The threshold of cerebral blood flow (CBF) into infarction in rats has been indicated to be similar to that in patients. However, CBF does not reflect metabolic function, and so estimations of oxygen metabolism have been required. Here, we estimated changes in oxygen metabolism after occluding the right middle cerebral artery (MCA) in rats using an injectable O-15-O-2 we developed. A decrease in CBF (left: 0.67 +/- 0.22 mL/min/g, right: 0.44 +/- 0.17 mL/min/g, P < 0.05) and compensatory increase in the oxygen extraction fraction (OEF) (left: 0.42 +/- 0.13, right: 0.50 +/- 0.19, P < 0.05) were observed at 1-h after occlusion. In contrast, a marked decrease in CBF and the cerebral metabolic rate for oxygen and a collapse of the compensatory OEF mechanism were found at 24 h after occlusion. Injectable O-15-O-2 could be used to reliably estimate oxygen metabolism in an infarction rat model with positron emission tomography.