Journal Article

Thyroid status and postnatal changes in subsarcolemmal distribution and isoform expression of rat cardiac dihydropyridine receptors

Maurice Wibo, Olivier Feron, Lei Zheng, Mehdi Maleki, Frantisek Kolar and Théophile Godfraind

in Cardiovascular Research

Published on behalf of European Society of Cardiology

Volume 37, issue 1, pages 151-159
Published in print January 1998 | ISSN: 0008-6363
Published online January 1998 | e-ISSN: 1755-3245 | DOI:
Thyroid status and postnatal changes in subsarcolemmal distribution and isoform expression of rat cardiac dihydropyridine receptors

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Objective: The aim was to analyze the early postnatal changes in myocardial density, subsarcolemmal localization and isoform expression of dihydropyridine receptors in rat ventricle and the influence of thyroid status on these changes. Methods: Newborn rats were treated from postnatal day 2 with L-triiodothyronine (T3) or 6-n-propyl-2-thiouracil (PTU) and ventricles were collected on day 1, 7 and 14. Radioligand binding and cell fractionation (density gradient centrifugation) techniques were used to determine the tissue density of various receptors and their subcellular localization. To analyze dihydropyridine receptor α1 subunit isoform expression, cDNA fragments corresponding to a large portion of motif IV were amplified by reverse transcriptase-polymerase chain reaction and treated with appropriate restriction endonucleases to determine the frequency of splicing events at the level of motif IV. Results: The myocardial density of dihydropyridine receptors increased 3-fold from day 1 to day 14 in control rats, and this increase occurred predominantly in membrane entities equilibrating at high densities in sucrose gradient, that is, presumably, in junctional structures (dyadic couplings). This maturation was delayed after PTU-treatment, and somewhat accelerated by excess T3. The proportion of mRNA variants typical of foetal heart (IVS3A variant and ‘deleted’ variant, showing a 33-nucleotide deletion at the level of the extracellular loop between IVS3 and IVS4) decreased with age in control rats. This reduction was delayed after treatment with PTU but was not influenced by excess T3. Conclusion: Hypothyroidism impaired the early postnatal maturation of dihydropyridine receptors as regards both their concentration into junctional structures and the decrease in the relative expression of α1-subunit mRNA variants typical of foetal heart.

Keywords: Rat heart; Development; Thyroid hormone; Junctional structures; Calcium channel; Dihydropyridine receptor; α1 subunit; Ryanodine

Journal Article.  6198 words.  Illustrated.

Subjects: Cardiovascular Medicine

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