Clot JP, Baudry M. Effect of thyroidectomy on oxidative phosphorylation mechanisms in rat liver mitochondria.
Mol Cell Endocrinol 1982;
28:455-69. [PMID:
6130011 DOI:
10.1016/0303-7207(82)90139-3]
[Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
(1) In the presence of succinate, 2,4-dinitrophenol raised the oxygen consumption rate of state 3 liver mitochondria, whatever the thyroid state. The rise was clearly greater in thyroidectomized than in normal rats, but the uncoupled state 3 mitochondria of thyroidectomized rats nevertheless consumed oxygen more slowly than normal rat mitochondria. Thyroidectomy therefore weakened respiratory chain activity and phosphorylation reactions. (2) With beta-hydroxybutyrate as substrate, oxygen consumption V of state 3 mitochondria was greatly diminished in thyroidectomized rats, but the KM remained unchanged. In the presence of succinate, state 3 respiration was not affected by thyroidectomy when substrate concentrations were low, but diminished at concentrations above 3 mM. (3) Respiratory chain activity was estimated by determining the succinate cytochrome c reductase activity. After thyroidectomy, catalytic efficiency (V/KM) dropped by 60% in intact mitochondria at high concentrations of the substrate, but only by 30% when concentrations were low. In submitochondrial particles, thyroidectomy reduced V without changing KM. These results suggest that in thyroidectomized rats, succinate penetration is faster when substrate concentrations are low. (4) Mg2+ -stimulated ATPase activity dropped by 20% in thyroidectomized rats. In the presence of increasing concentrations of oligomycin, inhibition of ATPase activity was greater in normal than in thyroidectomized rat mitochondria. Thyroidectomy reduced by over 30% the ATPase activity actually involved in oxidative phosphorylation.
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