| Popis: |
Cellular redox is intricately linked to energy production and normal cell function. Although the redox state of mitochondria and cytosol are connected by shuttle mechanisms, the redox state of mitochondria may differ from redox in the cytosol in response to stress. However, detecting these differences in functioning tissue is difficult. Here, we employed (13)C magnetic resonance spectroscopy (MRS) and co-polarized [1-(13)C]pyruvate and [1,3-(13)C(2)]acetoacetate ([1,3-(13)C(2)]AcAc) to monitor production of hyperpolarized (HP) lactate and β-hydroxybutyrate as indicators of cytosolic and mitochondrial redox, respectively. Isolated rat hearts were examined under normoxic conditions, during low-flow ischemia, and after pretreatment with either aminooxyacetate (AOA) or rotenone. All interventions were associated with an increase in [Pi]/[ATP] measured by (31)P NMR. In well-oxygenated untreated hearts, rapid conversion of HP [1-(13)C]pyruvate to [1-(13)C]lactate and [1,3-(13)C(2)]AcAc to [1,3-(13)C(2)]β-hydroxybutyrate ([1,3-(13)C(2)]β-HB) was readily detected. A significant increase in HP [1,3-(13)C(2)]β-HB but not [1-(13)C]lactate was observed in rotenone-treated and ischemic hearts, consistent with an increase in mitochondrial NADH but not cytosolic NADH. AOA treatments did not alter the productions of HP [1-(13)C]lactate or [1,3-(13)C(2)]β-HB. This study demonstrates that biomarkers of mitochondrial and cytosolic redox may be detected simultaneously in functioning tissue using co-polarized [1-(13)C]pyruvate and [1,3-(13)C(2)]AcAc and (13)C MRS, and that changes in mitochondrial redox may precede changes in cytosolic redox. |
