Vitamin E administration attenuates the tri-iodothyronine-induced modification of heart electrical activity in the rat.
This work was designed to determine whether the thyroid-hormone-induced modifications of heart electrical activity are, at least in part, due to increased free radical production. For this study, 60-day-old euthyroid, hyperthyroid and hyperthyroid vitamin-E-treated rats were used. Hyperthyroidism, elicited by a 10 day treatment with tri-iodothyronine, induced an increase in lipid peroxidation without changing the level of antioxidants. Intraperitoneal vitamin administration to hyperthyroid rats led to a reduction in lipid peroxidation and a non-significant increase in antioxidant level. The hyperthyroid state was also associated with an increase in heart rate measured in vivo and a decrease in the duration of the ventricular action potential recorded in vitro. Administration of vitamin E attenuated the thyroid-hormone-induced changes in heart rate and action potential duration, which were, however, significantly different from those of the control euthyroid rats. These results suggest that vitamin E protects hyperthyroid heart against lipid peroxidation by mechanisms that may be independent of the changes in antioxidant systems. Moreover, the reduction in the tri-iodothyronine effects on heart electrophysiological properties indicates that such effects are mediated, at least in part, through a membrane modification, probably related to increased lipid peroxidation, involving a free radical mechanism.
Venditti
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Dipartimento di Fisiologia Generale ed Ambientale di Napoli, Italy.
De Leo
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Di Meo
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D000200:Action Potentials; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D004347:Drug Interactions; D004594:Electrophysiology; D006321:Heart / Q000187:drug effects* / Q000502:physiology*; D006339:Heart Rate; D006352:Heart Ventricles / Q000503:physiopathology; D006980:Hyperthyroidism / Q000503:physiopathology; D007037:Hypothyroidism / Q000503:physiopathology; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014284:Triiodothyronine / Q000494:pharmacology*; D014810:Vitamin E / Q000008:administration & dosage* / Q000494:pharmacology
D000975:Antioxidants; D014284:Triiodothyronine; D014810:Vitamin E