In vivo estimation of cerebral blood flow, oxygen consumption and glucose metabolism in the pig by [ 15O]water injection, [ 15O]oxygen inhalation and dual injections of [ 18F]fluorodeoxyglucose

Abstract

There is a need for suitable non-primate laboratory animals for studies of brain function by positron emission tomography (PET). To provide a comparative index of the circulatory physiology of the pig, we have applied novel PET tracer methodology to seven anaesthetized pigs, and measured cerebral regional oxygen consumption (CMR O 2 ), cerebral blood flow (CBF), and cerebral glucose metabolism (CMR glc). Blood flow and flow-metabolism couple were estimated for selected cerebral regions of interest. We found an average hemispheric CMR O 2 of 171±18 μmol/100 cm 3/min. Individual hemispheric CBF measurements varied between 33 and 41 ml/100 cm 3/min, with an average of 37±3 ml/100 cm 3/min at an average Pa CO 2 of 4.3±0.9 kPa. The blood flow dependency on arterial P CO 2 was calculated from the results of the carbon dioxide response in two pigs in which the CBF measurements obeyed the equation CBF (ml/100 cm 3/min)=8.9 Pa CO 2 (kPa). In each pig, CMR glc was studied twice with a double-injection FDG method. In the first session, the values of CMR glc averaged 27±3 and 23±4 μmol/100 cm 3/min, estimated by multilinear and linear regression analysis, respectively. In the second session, the corresponding averages were 27±3 and 24±3 μmol/100 cm 3/min, respectively. The average oxygen extraction fraction was 0.46±0.09 and the oxygen-glucose ratio was 6.1±0.8. The findings indicate that the pig is suitable for PET studies of cerebral blood flow, cerebral oxygen consumption and glucose metabolism.