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Cellular mitochondrial heterogeneity in cultured astrocytes as demonstrated by immunogold labeling of α‐ketoglutarate dehydrogenase
Author(s) -
Waagepetersen Helle S.,
Hansen Gert H.,
Fenger Kirsten,
Lindsay J. Gordon,
Gibson Gary,
Schousboe Arne
Publication year - 2005
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.20276
Subject(s) - immunogold labelling , biology , mitochondrion , cerebellum , isocitrate dehydrogenase , citric acid cycle , microbiology and biotechnology , astrocyte , biochemistry , enzyme , neuroscience , ultrastructure , central nervous system , anatomy
In brain cells, various metabolites and metabolic pathways, largely of mitochondrial origin, have been shown to be compartmentalized. Attention has therefore been focused on the possible existence of mitochondrial heterogeneity in the brain at the cellular level. To determine whether mitochondria in cultured cortical and cerebellar astrocytes are heterogeneous at the single cell level, immunogold electron microscopy and an antibody against the α‐ketoglutarate dehydrogenase component of the α‐ketoglutarate dehydrogenase complex, a marker enzyme for the tricarboxylic acid (TCA) cycle, were employed. The number of gold particles was counted in the mitochondria of 36 and 42 cells from cultured cerebellar and cortical astrocytes, respectively. A test for random distribution (Poisson distribution) of mitochondria according to the number of gold particles was subsequently performed for every one of the 36 and 42 cells as the ratio variance/mean (= index of dispersion). This should be approximately distributed as χ 2 /degrees of freedom (df) = n − 1, n = number of mitochondria), if the observations obeyed a Poisson distribution. For 26 of the 36 (cerebellar astrocytes) distributions and for 28 of the 42 (cortical astrocytes) distributions a random distribution had to be rejected. These findings therefore strongly indicate that α‐ketoglutarate dehydrogenase is heterogeneously distributed in mitochondria within individual astrocytes originating either from cerebellum or cerebral cortex. In conclusion, this study underlines the probability that mitochondrial heterogeneity at the single cell level might be extended to involve other metabolic pathways and metabolites. © 2005 Wiley‐Liss, Inc.