title: In-vivo positron emission tomography (PET) measurement of cerebral oxygen metabolism in small animals.
abstract: The cerebral metabolic rate for oxygen (CMRO(2)) and cerebral oxygen extraction fraction (OEF) are two fundamental parameters used to characterize the pathophysiologic status of cerebral tissues. Although the O-15-labeled gas inhalation method is used to measure these parameters in clinical studies, applying this method to small animals requires many intensive procedures. Thus the development of a new method to measure CMRO(2) and OEF in small animals is of interest. This study aimed to develop a method to assess CMRO(2) and OEF using intravenously injectable oxygen (injectable (15)O-O(2)) and Positron Emission Tomography (PET) for small animals such as rats. Injectable (15)O-O(2) was obtained after (15)O-O(2) gas circulation into an artificial lung. The OEF in normal rats was calculated using the same equation as that used for the bolus inhalation in the (15)O-O(2) gas method. The obtained value of 0.54+/-0.11 of OEF was similar to the value determined from the arterial-venous difference in the oxygen concentration. Furthermore, we evaluated the usefulness of the injectable (15)O-O(2) system in rats occluded in the right middle cerebral artery. A decrease in cerebral blood flow (CBF) and compensatory increase in OEF were observed 1 h after occlusion. In contrast, a marked decrease in CBF and CMRO(2) and a collapse of the compensatory OEF mechanism were found 24 h after occlusion. Thus injectable (15)O-O(2) with PET can be used to estimate oxygen metabolism reliably in stroke animal models, and may be useful for accelerating basic research on cerebral diseases.
authors.affiliation: Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto, Japan. ttemma@pharm.kyoto-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Temma