V. Drvota, DOWN-REGULATION OF THYROID-HORMONE RECEPTOR SUBTYPE MESSENGER-RNA LEVELS BY RETINOIC ACID IN CULTURED CARDIOMYOCYTES, Biochemical and biophysical research communications, 242(3), 1998, pp. 593-596
The thyroid hormone receptors (TR) and the retinoic acid receptors sha
re a high degree of homology and their signaling pathways interplay. T
hyroid hormone (T3) is known to be associated with various pathologica
l heart conditions. Retinoids are known to ameliorate symptoms in hype
rthyroid patients. The aim of this study was to investigate if retinoi
c acid (RA) can have any effects on TR in cardiac cells and thus play
a role in heart disease. Confluent AT-1 cardiomyocytes were treated wi
th RA, T3 depleted medium and DITPA (a cardiotonic T3 analogue) for 48
hours, Solution hybridization for the determination of mRNA for TR al
pha(1), alpha(1), beta(1) and beta(2) was performed. RA, T3 and DITPA
significantly downregulated the alpha(1), beta(1) and beta(2). The T3
depleted medium did not affect the TR subtypes. The specificity of the
solution hybridization method was tested by an RNase protection assay
. In conclusion, RA downregulates TR in a similar way as T3 in cardiac
cells, indicating a role for RA in thyroid associated heart disease.
(C) 1998 Academic Press.