Age- and gender-related differences in mitochondrial oxygen consumption and calcium with cardioplegia and diazoxide.
BACKGROUND
We have recently shown that the cardioprotection afforded by cardioplegia is affected by age and gender and is less effective in the aged female rabbit heart compared with the aged male rabbit heart. We hypothesized that these differences were due to age and gender-specific modulation of mitochondrial oxygen consumption and mitochondrial free matrix calcium ([Ca2+](Mito)) content occurring during early reperfusion.


METHODS
To test this hypothesis, 104 male and female rabbit hearts, mature (15 to 20 weeks) and aged (>32 months), were subjected to Langendorff perfusion. Control hearts were perfused for 75 minutes. Global ischemia hearts were underwent 30 minutes of equilibrium, 30 minutes of global ischemia, and 15 minutes of reperfusion. Cardioplegia (potassium/magnesium) +/- diazoxide was infused 5 minutes before global ischemia. Mitochondria were isolated from left ventricular tissue and used for the measurement of oxygen consumption and [Ca2+](Mito).


RESULTS
Mitochondrial oxygen consumption was significantly increased in the mature and aged female hearts in all treatment groups (p < 0.001 versus male). Cardioplegia +/- diazoxide modulated mitochondrial oxygen consumption, but these effects were significantly decreased in the aged heart and in the female heart (p < 0.001 each versus male). Cardioplegia (potassium/magnesium) significantly decreased [Ca2+](Mito) (p < 0.001 versus global ischemia) in aged but not mature hearts. The addition of diazoxide to potassium/magnesium significantly decreased [Ca2+](Mito) in mature and aged males (p < 0.001 versus potassium/magnesium) but not in females.


CONCLUSIONS
These results demonstrate that mitochondrial oxygen consumption and [Ca2+](Mito) are modulated by age and gender and play an important role in the differences observed between mature and aged male and female response to global ischemia and the cardioprotection afforded by cardioplegia +/- diazoxide.
McCully
James D
JD
Division of Cardiothoracic Surgery, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Harvard Medical School, Boston, Massachusetts 02115, USA. james_mccully@hms.harvard.edu
Rousou
Anthony J
AJ
Parker
Robert A
RA
Levitsky
Sidney
S
D000255:Adenosine Triphosphate / Q000378:metabolism; D000367:Age Factors; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002314:Cardioplegic Solutions / Q000494:pharmacology*; D003981:Diazoxide / Q000494:pharmacology*; D004338:Drug Combinations; D005260:Female; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D015425:Myocardial Reperfusion; D015428:Myocardial Reperfusion Injury / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012737:Sex Factors; D013997:Time Factors
D002314:Cardioplegic Solutions; D004338:Drug Combinations; D000255:Adenosine Triphosphate; D008274:Magnesium; D003981:Diazoxide; D011188:Potassium; D002118:Calcium