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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
5-6
|
| pubmed:dateCreated |
1983-4-7
|
| pubmed:abstractText |
The 2-oxoglutarate dehydrogenase of intact rat heart mitochondria is activated by Ca2+, with 50% activation at approximately 0.5 nmol of total Ca/mg of mitochondrial protein, in the presence of Pi and Mg2+. Mitochondrial Ca contents in excess of 2 nmol/mg of protein result in 100% activation of the enzyme. Investigation of Ca2+ release from the mitochondria using the metallochromic indicator Arsenazo III defines a S0.5 of 5.4 +/- 0.4 nmol of Ca/mg of protein, when the endogenous Ca content of the mitochondria is progressively depleted with EGTA, prior to the initiation of the release process being studied. The subsequent determination of matrix free Ca2+ concentration by the "null-point" technique has allowed expression of these results in terms of free concentration rather than Ca content, with an activity coefficient of approximately 0.001 for matrix Ca2+. From the above, Ca2+ efflux from heart mitochondria is not saturated at the mitochondrial Ca contents or Ca2+ concentrations which give effective regulation of dehydrogenase activity. A consequence is that heart mitochondria do not buffer the pCa of the extramitochondrial medium at these Ca contents (less than 2 nmol/mg of protein), and this is shown in direct measurements of extramitochondrial pCa. This is taken to question the physiological significance of mitochondrial buffering of cytosolic free Ca2+ in normal heart.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Dec
|
| pubmed:issn |
0145-479X
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:volume |
14
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
361-76
|
| pubmed:dateRevised |
2006-11-15
|
| pubmed:meshHeading | |
| pubmed:year |
1982
|
| pubmed:articleTitle |
Intramitochondrial and extramitochondrial free calcium ion concentrations of suspensions of heart mitochondria with very low, plausibly physiological, contents of total calcium.
|
| pubmed:publicationType |
Journal Article,
In Vitro
|