[OPTICAL REVIEW Vol. 10, No. 5 (2003) 440-443]
© 2003 The Optical Society of Japan

Light Scattering Changes in Isolated Brain Mitochondria during Anoxia - Magnesium Effect on Morphological Changes and Respiration -

Fumihiko FUJII and Mamoru TAMURA

Biophysics, Research Institute for Electronic Science, Hokkaido University, N12 W6, Kita-ku, Sapporo 060-0812, Japan

(Received February 27, 2003; Accepted April 14, 2003)

Under pathological conditions, morphological changes of the cells and tissues may differ from those of normal conditions, which can be reflected by changes in light scattering (LS). Consequently, LS has been recognized as a potential non-invasive tool for optical diagnosis of living tissue. This paper aimed to identify the basic properties of LS of isolated brain mitochondria in vitro under normoxic and anoxic conditions in the presence and absence of Mg2+. An increase in LS was observed during anoxia in both the presence and absence of Mg2+. In both cases, the changes in LS initiated by anoxia and reoxygenation started concomitantly with the reduction of heme aa3. The rates of LS changes were slower than those of heme aa3, particularly in the presence of Mg2+. Mg2+ inhibited the morphological responses of mitochondria caused by the addition of ADP and ATP, and significantly reduced the oxygen consumption rate in state 4. These results are due to modulation of the K+/H+ antiporter affected by Mg2+. In addition, the mitochondria were well coupled, although the basal level of LS fell after addition of Mg2+. Therefore, the observed responses of mitochondria at anoxia were physiological and independent of the presence or absence of Mg2+. The relationship between LS and redox state of cytochrome c oxidase, an anoxic indicator, provides a basis to assess the tissue conditions in vivo.

Key words: light scattering, brain mitochondria, Mg2+