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Comparison of Different Mathematical Approaches to Assess Calcium Retention Capacity in Cardiac Isolated Mitochondria following Ischemia Reperfusion Injury
Author(s) -
Lahil Harjeev S.,
Salzman Michele M.,
Balzer Claudius,
Cleveland William J.,
Riess Matthias L.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.618.6
Subject(s) - mptp , mitochondrial permeability transition pore , mitochondrion , ischemia , chemistry , calcium , bolus (digestion) , reactive oxygen species , medicine , cardioprotection , endocrinology , biochemistry , apoptosis , dopaminergic , programmed cell death , dopamine
A hallmark of myocardial ischemia reperfusion (IR) injury is mitochondrial (m) dysfunction resulting in, e.g., altered electron transport, increased reactive oxygen species formation, decreased adenosine triphosphate synthesis and reduced calcium (Ca 2+ ) retention capacity (CRC). Different cardioprotective strategies aim to attenuate this dysfunction. CRC is typically assessed by adding boluses of extra‐mCa 2+ which is taken up by functioning mitochondria to a higher degree, leading to a later opening of the mitochondrial permeability transition pore (mPTP) and release of accumulated intra‐mCa 2+ than by damaged mitochondria. We hypothesized that mPTP opening could be predicted by the degree of decrease in the rate of mCa 2+ uptake after each exogenous Ca 2+ bolus before the mPTP opens. Following IR with and without different cardioprotective stratetgies, mitochondria were isolated from Brown Norway rat (n=38) and Arctic Ground Squirrel (n=19) isolated hearts, and CRC was assessed by measuring changes of extra‐mCa 2+ by calcium‐green fluorescence when repeated boluses of exogenous Ca 2+ were given in the presence of pyruvate/malate or succinate as complex I or II substrates, respectively. Multiple regression analyses (alpha 0.05) were used to compare the actual number of Ca 2+ boluses leading to mPTP opening to the number predicted from absolute mCa 2+ uptake and %mCa 2+ uptake, respectively. There were no significant differences in regressions between species. Despite acceptable regression coefficients (R 2 : 0.81/0.81 vs 0.76/0.78), both methods (absolute/%) had a regression slope significantly higher than 1.0 (slope±SEM: 1.28±0.08/1.35±0.09 vs 1.72±0.13/2.00±0.14) for complex I vs II substrates, respectively. This indicates an increasing overestimation of CRC by either method compared to the actual number of boluses before mPTP opening, more so in less dysfunctional compared to more dysfunctional mitochondria. This overestimation was stronger in the presence of complex II vs I substrates. Thus, predictions of eventual mPTP opening from mCa 2+ uptake after individual exogenous Ca 2+ boluses are more reliable in dysfunctional vs functional mitochondria and when complex I substrate is used compared to complex II substrate. Support or Funding Information Merit Review Award (IK2 BX001278 and I01 BX003482) from the United States Department of Veterans Affairs Biomedical Laboratory R&D Service; National Institutes of Health (5R01 HL123227) and institutional funds. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .