Chweih 2015 Exp Physiol

From Bioblast
Publications in the MiPMap
Chweih H, Castilho RF, Figueira TR (2015) Tissue and sex specificities in Ca(2+) handling by isolated mitochondria in conditions avoiding the permeability transition. Exp Physiol 100(9):1073-92.

Β» PMID: 26096641

Chweih H, Castilho RF, Figueira TR (2015) Exp Physiol

Abstract: What is the central question of this study? The assessment of Ca(2+) handling by isolated mitochondria can be biased by dysfunctions secondary to Ca(2+) -induced mitochondrial permeability transition (MPT). As a result of this uncertainty and the differing experimental conditions between studies, the tissue and sex diversities in mitochondrial Ca(2+) transport are still unsettled questions. What is the main finding and its importance? If MPT is not prevented during Ca(2+) transport assays, some measured variables are biased. Accounting for the implied importance of preventing MPT, we observed substantial tissue specificities in the mitochondrial Ca(2+) handling, particularly in the Ca(2+) efflux pathways. The characteristics of mitochondria, including their Ca(2+) transport functions, may exhibit tissue specificity and sexual dimorphism. Given that measurements of Ca(2+) handling by isolated mitochondria may be biased by dysfunction secondary to Ca(2+) -induced mitochondrial permeability transition (MPT) pore opening, this study evaluated the extent to which MPT inhibition by ciclosporin affected the measurement of Ca(2+) transport in isolated rat liver mitochondria. The results indicate that the steady-state levels of external Ca(2+) and the rates of mitochondrial Ca(2+) efflux through the selective pathways can be overestimated by up to fourfold if MPT pore opening is not prevented. We analysed Ca(2+) transport in isolated mitochondria from the liver, skeletal muscle, heart and brain of male and female rats in incubation conditions containing MPT inhibitors, NAD-linked substrates and relevant levels of free Ca(2+) , Mg(2+) and Na(+) . The Ca(2+) influx rates were similar among the samples, except that the liver mitochondria displayed values fourfold higher. In contrast, the Ca(2+) efflux rates exhibited more tissue diversity, especially in the presence of Na(+) . Interestingly, the Na(+) -independent Ca(2+) efflux was highest in the heart mitochondria (∼4 nmol mg(-1) min(-1) ), thus challenging the view that cardiac mitochondrial Ca(2+) efflux relies almost exclusively on a Na(+) -dependent pathway. Sex specificity was observed in only two kinetic indexes of heart mitochondrial Ca(2+) homeostasis and in the ADP-stimulated respiration of liver mitochondria (∼20% higher in females). The present study shows the methodological importance of preventing MPT when measuring the properties and the physiological variability of the Ca(2+) handling by isolated mitochondria.

β€’ O2k-Network Lab: BR Campinas Vercesi AE

Labels: MiParea: Respiration, mt-Membrane 

Stress:Permeability transition  Organism: Rat  Tissue;cell: Heart, Skeletal muscle, Nervous system, Liver  Preparation: Isolated mitochondria 

Coupling state: LEAK, OXPHOS  Pathway:HRR: Oxygraph-2k 

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