(17) A COMPARISON OF THE OXIDATION STATE OF INTRAMITOCHONDRIAL Mn UNDER CONDITIONS CHOSEN TO INDUCE OXIDATION AND BETWEEN BRAIN, HEART, AND LIVER MITOCHONDRIA

K.K. Gunter, L.M. Miller, A. Alexandrov, L. Buntinas, R. Eliseev and T.E. Gunter
Department of Biochemistry and Biophysics, University of Rochester Medical School, Rochester, NY 14642

X-ray near edge structure (XANES) spectroscopy has been used to determine the oxidation state and complexes of intramitochondrial Mn over a range of concentrations, was incubated for 10 and 120 min in mitochondria which had previously sequestered 40 nmoles Ca2+/mg protein.  Intramitochondrial Mn over a range of concentrations, was also incubated for 10 and 120 min during periodic stimulation of electron transport by addition of ADP and inorganic phosphate.  Under all of these conditions, XANES spectroscopy indicated that intramitochondrial Mn remained in the 2+ oxidation state.

It is currently impractical to isolate the quantities of brain mitochondria necessary for sensitive XANES studies from small regions of the brain such as striatum or globus pallidus in order to determine whether pools of intramitochondrial Mn in those brain regions differed significantly from those in mitochondria prepared from whole brain.  However, we reasoned that if the intramitochondrial Mn pools in brain, heart, and liver mitochondria were very similar, the chance that Mn pools in mitochondria from any component of these organs would differ significantly was small.  XANES spectroscopy shows that the Mn oxidation state and complexes of intramitochondrial Mn in brain mitochondria are almost identical to those in liver and heart mitochondria.

This work was supported by HEI contract 99-11 and by a pilot grant from NIEHS Center Grant P30-ES01247.

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