Horm Metab Res 2003; 35(1): 55-61
DOI: 10.1055/s-2003-38392
Original Clinical
© Georg Thieme Verlag Stuttgart · New York

Effects of Thyroid State on H2O2 Production by Rat Heart Mitochondria: Sites of Production with Complex I- and Complex II-Linked Substrates

P.  Venditti1 , A.  Puca1 , S.  Di Meo1
  • 1Dipartimento di Fisiologia Generale ed Ambientale, Università di Napoli, Italy
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Publikationsverlauf

Received 8 May 2002

Accepted after revision 3 September 2002

Publikationsdatum:
01. April 2003 (online)

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Abstract

This work was designed to determine possible effects of altered thyroid states on rates and sites of H2O2 production by rat heart mitochondria. Rates of O2 consumption and H2O2 release, capacities to remove the peroxide, lipid peroxidation, cytochrome oxidase activities and ubiquinone levels were determined in heart mitochondria from euthyroid, hypothyroid, and hyperthyroid rats. Hypothyroidism decreased, whereas hyperthyroidism increased the rates of O2 consumption and H2O2 release during both state 4 and state 3 respiration with Complex I- or Complex II-linked substrates. The percentage of O2 released as H2O2 was not significantly affected by thyroid state. However, the mitochondrial capacity to remove H2O2 increased in the transition from hypothyroid to hyperthyroid state, which indicates that H2O2 production did not modify in proportion to the rate of O2 consumption. The thyroid-state-linked changes in H2O2 production were well correlated with the levels of hydroperoxides. Rates of H2O2 release in the presence of respiratory inhibitors indicated that changes in the H2O2 production occurred at both sites at which H2O2 was generated in euthyroid state. This result and the observation that ubiquinol levels and cytochrome oxidase activities increase in the transition from hypothyroid to hyperthyroid state suggest that the modifications of H2O2 production are due to a modulation by thyroid hormone of mitochondrial content of autoxidisable electron carriers.

References

Dr. S. Di Meo

Dipartimento di Fisiologia Generale ed Ambientale · Università di Napoli “Federico II” ·

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