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Why to compare absolute numbers of mitochondria.

Mitochondrion 19, 113-123 (2014)
Postprint DOI
Open Access Green
Prompted by pronounced structural differences between rat liver and rat hepatocellular carcinoma mitochondria, we suspected these mitochondrial populations to differ massively in their molecular composition. Aiming to reveal these mitochondrial differences, we came across the issue on how to normalize such comparisons and decided to focus on the absolute number of mitochondria. To this end, fluorescently stained mitochondria were quantified by flow cytometry. For rat liver mitochondria, this approach resulted in mitochondrial protein contents comparable to earlier reports using alternative methods. We determined similar protein contents for rat liver, heart and kidney mitochondria. In contrast, however, lower protein contents were determined for rat brain mitochondria and for mitochondria from the rat hepatocellular carcinoma cell line McA 7777. This result challenges mitochondrial comparisons that rely on equal protein amounts as a typical normalization method. Exemplarily, we therefore compared the activity and susceptibility towards inhibition of complex II of rat liver and hepatocellular carcinoma mitochondria and obtained significant discrepancies by either normalizing to protein amount or to absolute mitochondrial number. Importantly, the latter normalization, in contrast to the former, demonstrated a lower complex II activity and higher susceptibility towards inhibition in hepatocellular carcinoma mitochondria compared to liver mitochondria. These findings demonstrate that solely normalizing to protein amount may obscure essential molecular differences between mitochondrial populations.
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Publication type Article: Journal article
Document type Scientific Article
Keywords Metabolic Shift ; Mitochondria ; Mitochondrial Number ; Mitochondrial Protein Content ; Respiratory Complex Ii
ISSN (print) / ISBN 1567-7249
e-ISSN 1872-8278
Journal Mitochondrion
Quellenangaben Volume: 19, Issue: , Pages: 113-123 Article Number: , Supplement: ,
Publisher Elsevier
Reviewing status Peer reviewed