BRAIN CREATINE-KINASE WITH AGING IN F344 RATS - ANALYSIS BY SATURATION-TRANSFER MAGNETIC-RESONANCE SPECTROSCOPY

We measured in vivo forward flux of the creatine kinase reaction in ra t forebrain in young (Y: 6 month, n = 13), mid-aged (M: 12 month, n = 7) and aged (O: 27 month, n = 10) animals using 31P magnetic resonance saturation transfer. Forward flux was reduced in the aged rats (Y: 0. 42 +/- 0.08; M: 0.41 +/- 0.10; O: 0.31 +/- 0.03 s(-1) +/- SD; p = 0.00 8 O vs. Y). In vitro studies in a subset of the same rats showed a par allel decline in CK activity (Y: 2.16 +/- 0.40; M: 2.17 +/- 0.25; O: 1 .56 +/- 0.06 IU +/- S.D.; p = 0.002 O vs. Y). The in vivo spectroscopi c and in vitro biochemical measures were significantly correlated. Red uced creatine kinase activity could account for the observed decreased forward flux in aging brain. Intracellular pH, phosphocreatine/inorga nic phosphate ratio, and phospocreatine/gamma-adenosine triphosphate r atio did not differ between groups. Forward flux may represent a bette r measure of brain energy function than relative phosphocreatine or ad enosine triphosphate levels observable in vivo. (C) 1997 Elsevier Scie nce Inc.