Effects of amiodarone and thyroid dysfunction on myocardial calcium, serum calcium and thyroid hormones in the rat.
1 Myocardial calcium content was found to be elevated and serum calcium reduced in hypothyroid rats. 2 Treatment of rats with amiodarone at either 30 mg kg-1 or 150 mg kg-1 daily did not result in any significant changes in myocardial or serum calcium. 3 The administration of amiodarone to hypothyroid rats attenuated the changes in serum but not myocardial calcium, suggesting that amiodarone may exert a thyroid hormone-like effect in the hypothyroid state. 4 The administration of amiodarone to thyroid hormone-treated rats resulted in attenuation of the effects on serum calcium and calculated intracellular calcium; this was consistent with an antagonistic interaction between amiodarone and thyroid hormones. 5 Administration of amiodarone resulted in significant changes in circulating thyroid hormone levels in the rat; triiodothyronine was reduced and basal thyrotrophin elevated compared to euthyroid controls. Serum thyroxine was not changed; this is in contrast to the effects in man. 6 Amiodarone does not exert its anti-arrhythmic action via changes in total myocardial calcium content in the euthyroid rat; nonetheless the described interactions between the drug and thyroid hormones may be involved in its mechanism of action.
Gammage
M D
MD
Department of Physiology, University of Birmingham.
Franklyn
J A
JA
Logan
S D
SD
D000638:Amiodarone / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D007037:Hypothyroidism / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013959:Thyroid Diseases / Q000378:metabolism*; D013963:Thyroid Hormones / Q000097:blood*
D009124:Muscle Proteins; D013963:Thyroid Hormones; C036116:desethylamiodarone; D000638:Amiodarone; D002118:Calcium