Direct and Noninvasive Measurement of Cerebral Metabolic Rate of ATP in Cat Brain and Its Physiological Implications

Xiao-Hong Zhu¹, Yi Zhang¹, Kamil Ugurbil¹, Wei Chen¹

Adenosine triphosphate (ATP) metabolism provides energy at cellular level for all living species. In the brain, majority of ATP is formed in mitochondria through oxidative phosphorylation and utilized in cytosol for supporting normal brain function. By applying the in vivo ³¹P MRS in combine with the magnetization transfer (MT) approach, we are able to directly and non-invasively measure the cerebral metabolic rate of ATP (CMR_ATP) in cat brain at 9.4T. The results of the CMR_ATP measurement have been validated via: i) using different MT techniques; and ii) comparing with the estimated CMR_ATP derived from the CMRO₂ previously obtained from the same cat model. In addition, by correlating the experimentally determined CMR_ATP with the CMRO₂ values in cat, as well as in rat and human brain, we could obtain the P:O ratios in these species, which indicate that oxidative phosphorylation indeed dominates the ATP production in these resting brains.