Hypothyroid like effect of amiodarone on myosin isoenzymes of theventricular myocardium of the rat

Wiegand, V.; Oberschmidt, R.; Henniges, A.; Kreuzer, H. J.

doi:10.1016/s0022-2828(84)80512-x

Cited by 2 publications

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“…A decrease in the density of Padrenoceptors at the myocardial cell surface (Nokin et al, 1983;Sharma & Corr, 1983) and a reduction in myocardial oxygen consumption (Harris et al, 1986) have been demonstrated: the latter has been shown to be dose-related in the dog. Other effects include an increase in the ratio of V3 to VI myosin heavy chain isoenzymes (this could be reversed by the administration of T3) (Wiegand et al, 1984), a reduction in cardiac myosin-ATPase (Sogol et al, 1983) and a reduction in Na', K+-ATPase activity in rabbit and guinea-pig heart .…”

Section: Discussionmentioning

confidence: 99%

Effects of amiodarone and thyroid dysfunction on myocardial calcium, serum calcium and thyroid hormones in the rat

Gammage

Franklyn

Logan³

1987

British J Pharmacology

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1 Myocardial calcium content was found to be elevated and serum calcium reduced in hypothyroid rats.2 Treatment of rats with amiodarone at either 30mg kg-' or 150mg kg-' 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.

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Section: Discussionmentioning

confidence: 99%

Effects of amiodarone and thyroid dysfunction on myocardial calcium, serum calcium and thyroid hormones in the rat

Gammage

Franklyn

Logan³

1987

British J Pharmacology

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Local changes in myosin types in diseased human atrial myocardium: a quantitative immunofluorescence study.

Bouvagnet¹,

Dechesne²,

Dureau³

et al. 1985

Circulation

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Two monoclonal antibody groups were prepared from adult human atrial and ventricular myosin heavy chains. Using these two groups, we were able to identify two myosin variants in human atria and to classify human atrial fibers into a-, mixed, or /S-fibers according to the reactivity of the two monoclonal antibody groups to a-and /-myosin heavy chains of normal young and hypothyroid rat ventricles, respectively. The a-fiber percentage of the left atria in two normal human hearts was 15% higher than in the right atria. The auricles contained two to three times more a-fibers than /3-fibers, whereas the proportion was reversed in the crista terminalis. The mean fiber diameter of the aand /-fibers was 13.6 + 3 gm. A complete a-to /-fiber transition was observed in all atrial regions of two hearts with severe ventricular myocardial infarction; a moderate a-to /3-fiber transition was observed only in the left atria of two hearts with primary congestive cardiomyopathy. The mean diameters of the two fiber types were significantly increased in all diseased hearts (1 9 ± 3.8 ,gm). We hypothesize that pressure overload and increased wall tension successively induce an enlargement of the fiber diameter and an a-to /3-myosin transition. Circulation 72, No. 2, [272][273][274][275][276][277][278][279] 1985.AT LEAST TWO molecular variants of myosin heavy chains have been identified in normal human atrial myocardium by histochemical and indirect immunofluorescence studies involving polyclonal and monoclonal antibodies.>1 We have referred to the human atrial myosin, which reacts strongly with one set of our monoclonal antibodies, as "/3-like" atrial myosin since this set of monoclonal antibodies strongly reacts with ventricular,8-myosin in hypothyroid rats.3 This human atrial :-like myosin variant has been separated from the other myosin form by immunochromatography, and it has been shown that each form of human atrial myosin has a different primary structure but the same high enzymatic activity in vitro.5 No direct evidence concerning any immunologic cross-reactivity of the other human atrial myosin with rat ventricular a-myosin is available at present. The fibers containing either /3-like myosin or the other myosin form are not randomly distributed within the different regions of the atria in normal hearts, and marked changes in their local distributions have been described in diseased human hearts.2 3 Neither the distribution of the two fiber types in the different atrial regions nor their pathologic modifications have ever been quantified.In this study we used, for the first time, two groups of monoclonal antibodies that specifically detect each atrial myosin variant in the rat heart as well as in the human heart. We also quantified the fiber type distributions within different regions of the atria in two normal and four diseased human hearts. In the latter, different isomyosin distributions were shown to be related to different pathologic conditions. Materials and methodsPatients. Four adult human hearts were obtained...

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Hypothyroid like effect of amiodarone on myosin isoenzymes of theventricular myocardium of the rat

Cited by 2 publications

References 0 publications

Effects of amiodarone and thyroid dysfunction on myocardial calcium, serum calcium and thyroid hormones in the rat

Effects of amiodarone and thyroid dysfunction on myocardial calcium, serum calcium and thyroid hormones in the rat

Local changes in myosin types in diseased human atrial myocardium: a quantitative immunofluorescence study.

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