Spironolactone effects on myocardium changes induced by thyroid hormone in rats.
BACKGROUND
To study the possible role of aldosterone on thyroid hormone-induced myocardium hypertrophy, using spironolactone.


OBJECTIVE
To evaluate morphological changes in the myocardium induced by thyroid hormone and the possible effects of spironolactone use on these alterations.


METHODS
Forty Wistar rats were studied. The animals were allocated to four groups and were given: the vehicle used for dilution of the thyroid hormone (C); sodium levothyroxin at 50 microg/rat/day (H); spironolactone, 0.3 mg/kg/day (S); or thyroid hormone plus spironolactone (HS), at the same doses mentioned above, for 28 consecutive days. All the animals were weighed, had blood drawn for hormonal measurements and underwent ECG at the start and the end of the experiment. At the end of experiment all animals were euthanized, the weight of the left ventricle (LV) was determined and LV slices were obtained for morphological analysis.


RESULTS
There was an increase in T3 levels, decrease of body weight and higher heart rate in the animals from group H. The LV weight was significantly higher in the H e HS groups. The histometric analyses that measured the diameter of the myocytes showed higher values in group H and a progressive decrease in groups HS, S and C, with a significant difference among all the groups. The addition of spironolactone decreased the transversal myocyte hypertrophy by 14.6%.


CONCLUSIONS
Rats treated with thyroid hormone present cardiac hypertrophy with increased LV weight and greater myocyte diameter. Spironolactone, when associated with thyroid hormone, can partially prevent this hypertrophy through mechanisms that are yet to be determined.
Fernandes
Maria Luiza Mendonça Pereira
ML
Universidade Federal de Uberlândia, Uberlândia, MG, Brasil. mlfernandes@ufu.br
Ferro
Eloísa Amália Vieira
EA
Beletti
Marcelo Emilio
ME
Resende
Elmiro Santos
ES
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D017379:Hypertrophy, Left Ventricular / Q000139:chemically induced* / Q000517:prevention & control; D008297:Male; D000451:Mineralocorticoid Receptor Antagonists / Q000627:therapeutic use*; D023421:Models, Animal; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013148:Spironolactone / Q000627:therapeutic use*; D013963:Thyroid Hormones / Q000009:adverse effects* / Q000097:blood; D013974:Thyroxine / Q000009:adverse effects / Q000097:blood; D014284:Triiodothyronine / Q000009:adverse effects / Q000097:blood
D000451:Mineralocorticoid Receptor Antagonists; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013148:Spironolactone; D013974:Thyroxine