Effets de la thyroïdectomie du rat sur la structure et les fonctions des mitochondries des muscles squelettiques

doi:10.1016/S0300-9084(75)80052-6

Biochimie

Volume 57, Issues 6–7, 8 October 1975, Pages 779-786

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Summary

Mitochondria used in the present study were isolated from skeletal muscle of normal and thyroidectomized rats. The preparations were controlled by electron microscopy. It was not possible to find any morphological change induced by thyroidectomy, nevertheless, some differences appeared in the cytochrome contents which were slightly decreased.

Oxygen consumption rates of thyroidectomized rat mitochondria were decreased when the particles were maintained in states 3 and 4 in the presence of various substrates, but the P/O ratios were not modified. The activities of mitochondrial enzymes were in general slightly affected by thyroidectomy except for glycerol-1-phosphate cytochrome c reductase and NADH rotenone sensitive cytochrome c reductase which were decreased and for glutamate dehydrogenase activity which was increased. The tRNA nucleotidyltransferase activity found in the mitochondrial matrix was not influenced by the absence of thyroid secretion.

Normal rat muscle mitochondria incorporate ¹⁴C-leucine with an artificial ATP-generating system or with a respiratory substrate. The amino acid incorporation was decreased by thyroidectomy.

Muscle mitochondria analyzed by polyacrylamide gel electrophoresis contained more than 30 protein components with MW ranging from 10.000 to 135.000. Thyroidectomy lowered the amount of a fraction of about 54.000 MW. It is not impossible that all the data observed in the absence of thyroid secretion are in relation with changes induced in the mitochondrial genome as previously shown in mitochondria isolated from liver of thyroidectomized rats.

Résumé

Les recherches sont réalisées sur des mitochondries isolées de muscles squelettiques de rats normaux ou thyroïdectomisés. La pureté des préparations est contrôlée par examen au microscope électronique. Aucune différence morphologique n'apparaît entre les mitochondries de rats normaux et thyréoprives. Cependant des changements dans la structure particulaire se manifeste au niveau des cytochromes, puisque leur teneur est faiblement mais régulièrement abaissée chez l'animal thyroïdectomisé.

La vitesse respiratoire des mitochondries musculaires placées dans les états 3 et 4 et en présence de divers substrats est ralentie par la thyroïdectomie mais les rapports P/O ne sont pas modifiés. Les propriétés des enzymes mitochondriales sont généralement peu affectées par le défaut de sécrétion thyroïdienne sauf pour la glycérol-1-phosphate cytochrome c réductase et la NADH roténone sensible cytochrome c réductase qui sont diminuées et la glutamate déshydrogénase qui est au contraire augmentée. L'activité de la tRNA nucléotidyltransférase caractérisée, dans la matrice mitochondriale, n'est pas changée par la thyroïdectomie.

Les mitochondries musculaires de rats normaux incorporent de la leucine marquée en présence d'un système générateur artificiel d'ATP ou d'un substrat respiratoire. La thyroïdectomie ralentit la vitesse d'incorporation de l'acide aminé.

Les mitochondries de muscles analysées par électrophorèse sur gel de polyacrylamide renferment plus de trente constituants protéiques de PM compris entre 10 000 et 135 000. La thyroïdectomie diminue la teneur d'un constituant de PM 54 000 environ. Il n'est pas impossible que l'ensemble des faits observés en l'absence de sécrétion thyroïdienne soit en relation avec des modifications au niveau du génome mitochondrial, comme cela a été montré avec les particules d'origine hépatique.

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Cited by (4)

Effect of thyroidectomy on the rat adrenal cortex enzyme activities involved in corticosterone and aldosterone biosynthesis
1982, Journal of Steroid Biochemistry
The effect of thyroidectomy on corticosterone and aldosterone biosynthesis, in rat adrenal cortex, were investigated in vitro. Thyroidectomy slowed down by about 30% the activity of microsomal 21 hydroxylase and mitochondrial 11β hydroxylase, the two stages leading to corticosterone formation from progesterone. The plasma corticosterone concentration also diminished in thyroidectomized rat. The mitochondrial enzyme system catalyzing the conversion of corticosterone into aldosterone included both 18 hydroxylase and 180H dehydrogenase. In the absence of thyroid hormone, values of both enzyme activity slowed down by about 30%. Thus thyroidectomy induced a general decrease in all mitochondrial hydroxylation processes requiring NADPH as energetic cofactor.
Mitochondrial NADPH was mainly synthesized by the activity of NADP⁺malic enzyme and pyridine nucleotide transhydrogenase; the activity of both enzymes was determined in submitochondrial particles from adrenal cortex of normal and thyroidectomized rats. The activity of NADP⁺ malic enzyme and non energy-dependent transhydrogenase in the direction of NADPH formation dropped significantly after thyroidectomy, thus reducing the amount of NADPH available for hydroxylating mechanisms. The results should be compared to the large rise in the cytosolic malic enzyme level caused by thyroidectomy. The latter also ensured that the transhydrogenase reaction did not vary in the direction of NADP⁺ formation. Further, the drop in NADPH synthesis after thyroidectomy was coupled with a decrease in phosphorylation rate of added ADP by adrenal cortex mitochondria of thyroidectomized rat.
These findings might account for the general decline in the energy-dependent processes involved in steroidogenesis, a decline mainly due to the lowering of the H⁺ ions gradient driving ATP and NADPH synthesis through electron transfer.
Effect of thyroidectomy on the protein content of rat adrenal cortex mitochondria and microsomes
1978, Journal of Steroid Biochemistry
The effects of thyroidectomy on the protein content and properties of adrenorcortical mitochondria and microsomes were investigated in the rat. Thyroidectomy caused a drop in the cytochrome P450 concentration in both paniculate fractions. Polyacrylamidc get electrophoresis of mitochondrial and microsomal proteins showed a reduction in the protein constituent with a molecular weight of 52,000 daltons. This constituent corresponded to the cytochrome P450 subunit. Isolated adrenal cortex mitochondria from thyroidectomized rats incorporated 30% less leucine than normal mitochondria. Electrophoresis of labelled proteins showed no change in radioactivity distribution. In microsomes, the rate of 21-hydroxylase activity dropped by 30% after thyroidectomy.
Although these effects were similar to those observed after dexamethasone treatment, there was no doubt that they were caused by the absence of thyroid hormones, since no reduction was found in the plasma ACTH concentration in thyroidectomized animals. The drop in the content of cytochrome P450 in adrenal cortex mitochondria and microsomes could explain the diminished hydroxylating activity of these organelles.
Effect of thyroid state on lipid peroxidation, antioxidant defences, and susceptibility to oxidative stress in rat tissues
1997, Journal of Endocrinology
Effect of thyroid state on the morphofunctional properties of heart mitochondria
1992, Cellular Physiology and Biochemistry

^(*): Ce travail a été raéalisé en partie grâce à une subvention du CNRS.

^(**): Avec la collaboration technique de M^me B. Souillat (CNRS).

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Effets de la thyroïdectomie du rat sur la structure et les fonctions des mitochondries des muscles squelettiques(*)

Summary

Résumé

Arch. Biochem. Biophys.

J. Biol. Chem.

Biochimie

Biochimie

FEBS Lett.

J. Biol. Chem.

Arch. Biochem. Biophys.

Biochem. Pharmacol.

Methods in Enzymology

Biochim. Biophys. Acta

J. Biol. Chem.

Biochim. Biophys. Acta

Biochimie

Biochimie

Biochim. Biophys. Acta

Biochim. Biophys. Acta