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|Type:||Artigo de periódico|
|Title:||Changes in calcium uptake rate by rat cardiac mitochondria during postnatal development|
|Abstract:||Ca2+ uptake, transmembrane electrical potential (Delta psi m) and oxygen consumption were measured in isolated ventricular mitochondria of rats from 3 days to 5 months of age. Estimated values of ruthenium red-sensitive, succinate-supported maximal rate of Ca2+ uptake (V-max, expressed as nmol Ca2+/min/mg protein) were higher in neonates and gradually fell during postnatal development (from 475+/-24 at 3-6 days, to 156+/-10 in adults, P<0.001), whereas K-0.5 values (similar to 10 mu M) were not significantly affected by age. Under similar conditions, mitochondria from adults (5 months old) and neonates (4-6 days old) showed comparable state 4 (succinate and alpha-ketoglutarate as substrates) and state 3(ADP) (alpha-ketoglutarate-supported) respiration rates, as well as Delta psi m values (similar to-150 mV). Respiration-indpendent Delta psi m and Ca2+ uptake, supported by valinomycin-induced K+ efflux were also investigated at these ages. A transient Delta psi m (similar to-30 mV) was evoked by valinomycin in both neonatal and adult mitochondria. Respiration-independent Ca2+ uptake was also transient, but its initial rate was significantly higher in neonates than in adults (49.4+/-10.0 v 28.0+/-5.7 mmol Ca2+/min/mg protein, P<0.01). These results indicate that Ca2+ uptake capacity of rat cardiac mitochondria is remarkably high just after birth and declines over the first weeks of postnatal life, without change in apparent affinity of the transporter. Increased mitochondrial Ca2+ uptake rate in neonates appears to be related to the uniporter itself, rather than to modification of the driving force of the transport. (C) 1998 Academic Press.|
|Editor:||Academic Press Ltd|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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