Abstract
Objective: In view of their different actions on thyroid hormone receptor (TR) isoforms we set out to investigate whether amiodarone (AM) and dronedarone (Dron) have different and/or component-specific effects on cardiac gene expression.
Design: Rats were treated with AM or Dron and the expression of TRα 1, TRα 2, TRβ 1 and several tri-iodothyronine (T3)-regulated genes was studied in different parts of the heart, namely the right atrium (RA), left ventricular wall (LVW) and apex.
Methods: Rats were treated for 14 days with 100 mg/kg body weight AM or Dron. The expression of TRα 1, TRα 2, TRβ 1 and T3-regulated genes was studied using real-time PCR and non-radioactive in situ hybridisation.
Results: AM and Dron affected TR expression in the RA similarly by decreasing TRα 1 and β 1 expression by about 50%. In the LVW, AM and Dron decreased TRβ 1 and, interestingly, AM increased TRα 1. In the apex, AM also increased TRα 2. The changes seen in T3-dependent gene expression are reminiscent of foetal reprogramming.
Conclusion: Taken together, our results indicate that AM and Dron have similar effects on the expression of TR isoforms in the RA, which could partly contribute to their ability to decrease heart rate. On the other hand, the more profound effect of AM appears on TR- and T3-dependent gene expression in the left ventricle suggests foetal reprogramming.
Introduction
Thyroid hormone (TH) has profound effects on the heart via the different TH receptor isoforms, for example as a chronotrope. Specialised cells generate the rhythm and guide the impulse throughout the heart. The conduction system can be divided into the sinoatrial node (SAN), the atrioventricular node (AVN) and the peripheral ventricular conduction system (PVCS). From our recent studies, it has become apparent that the TH receptor (TR) isoforms α 1, α 2 and β 1 are expressed in a component-specific manner in the heart (2). In the mouse, it has been found that TRα 1 is important in setting heart rhythm and regulating the expression of genes important for cardiac function such as α-myosin heavy chain (α MHC; up-regulated by TH), β MHC (down-regulation reciprocal to α MHC), sarcoplasmic reticulum Ca-ATPase2a (SERCA2a; up-regulated by TH) and guanine nucleotide regulatory proteins (like HCN4; up-regulated by TH; (3, 4)). Furthermore, TRβ 1 appears to have a function in mediating the tri-iodothyronine (T3)-induced increase in the heart rate in the mouse (5). The situation is slightly different in the rat where it has been suggested that TRβ 1 also plays a role in the expression of SERCA2a and β MHC (6, 7).
We speculated whether the component-specific expression of TRs had any relation to certain TH antagonistic effects of the class III anti-arrhythmic drugs amiodarone (AM) and dronedarone (Dron). AM has been suggested to induce a localised hypothyroid condition in the heart (8), which is partlydue to its TR inhibitingaction (9, 10). Similarly Dron also appears to mimic hypothyroidism at the level of the heart (6, 11). Furthermore, it has been shown that a high dose of AM intensifies cardiac remodelling (12). Remodelling after cardiac failure by itself has been suggested to bring about a hypothyroid cardiac phenotype with accompanying changes in TR expression as well as changes in the expression of genes like SERCA (13). In the present study, we look at a combination of both phenomena on the expression of the TR isoforms α 1, α 2 and β 1, and the T3-dependent genes α and β MHC, SERCA2a, guanine nucleotide regulatory protein (HCN4) and atrial natriuretic factor (ANF) in the different components of the rat heart.
Materials and methods
In vivo studies
Male Wistar rats, divided into three groups (eight rats per group), were housed under normal conditions with free access to standard lab chow and tap water. The rats received either water (controls), an aqueous suspension of Dron 100 mg/kg body weight or AM 100 mg/kg body weight by gastric tubes daily for 2 weeks as described previously (11). Rats were anaesthetised and killed by i.p. infusion of 0.5 mg/kg medetomidine (Dormitor 1 mg/ml) and 0.75 mg/kg ketamine (Ketalar 10 mg/ml). Blood was collected by cardiac puncture and plasma was stored at − 20 ° C. The hearts were removed and washed in PBS. Five hearts of each group were dissected under a stereomicroscope into right atria, part of the left ventricle wall and cardiac apex. These components were immediately frozen and stored in liquid nitrogen for isolation of mRNA. Three hearts were washed in PBS and processed for in situ hybridisation. The animal experiments were approved by the animal welfare committee of the Academic Medical Centre, University of Amsterdam.
Plasma assays
Total thyroxine (T4) and T3 were measured by an in-house RIA (14), using rat null plasma as diluent. TSH was determined by Delfia fluoroimmunoassay (Perkin–Elmer Wallac GmbH, Freiburg, Germany). Plasma total cholesterol was measured using a fully enzymatic dye method (Modular P analyzer, Roche Molecular Biochemicals). All samples were measured in one run. Data are expressed as mean ± s.d.
mRNA analyses by real-time PCR
mRNA from the right atrium (RA), apex and left ventricular wall (LVW) was obtained with the MagNa Pure LC RNA Isolation Kit II (Tissue; Roche) using the MagNa Pure LC Instrument (Roche), after which cDNA was made using the first-strand cDNA synthesis kit (containing avian myeloblastosis virus (AMV) reverse transcriptase) on which real-time PCR was performed using the LightCycler (Roche). Primers were purchased from Biolegio BV (Malden, The Netherlands). TRα 1 and TRα 2 were quantified as described previously (15). For TRβ 1, primer sequences were as follows: forward, 5′-CACCTGGATCCTGACGATGT-3′ and reverse, 5′-AC-AGGTGATGCAGCGATAGT-3′ . SERCA2a was detected using the following primers: forward, 5′-ATGGACGA-GACGCTCAAGTT-3′ ; reverse, 5′-GAAGCGGTTACTC-CAGTATTGC-3′ ; ANF using forward, 5′-AACACA-GATCTGATGGATTTCAAG-3′ ; reverse, 5′-CGCTTCATC-GGTCTGCTC-3′ ; α MHC using forward, 5′-CTGCAGTCA-GCCCTGGAG-3′ ; reverse, 5′-GGAGGATCTTGCCCTCCT- 3′ ; β MHC using forward, 5′-CATCAAGGAGCTCACC-TACCA-3′ ; reverse, 5′-TCCTGCAGTCGCAGTAGGTT-3′ ; and finally HCN4 using forward, 5′-ATCCAGTCGCTG-GACTCCT-3′ ; reverse, 5′-TGTACTGCTCCACCTGCTTG-3′ .
Non-radioactive in situ hybridisation for T3-regulated genese
The hearts were processed for in situ hybridisation using a fixation protocol and digoxigenin (DIG)-labelled, single-strand RNA probes as described previously (16). All probes have also been described previously: SERCA2a (17), α MHC and β MHC (18), HCN4 (19) and ANF (20). Images of sections were taken using a digital camera Leica DFC 320 RZ 0793, coupled with a Zeiss Axiophot microscope, equipped with differential interference contrast optics.
Statistical analysis
Differences between groups in plasma TH parameters and body weights were evaluated using ANOVA followed by a t-test when the ANOVA appeared significant to identify individual changes. Differences between groups in mRNA levels were evaluated using the Mann–Whitney test.
Results
Plasma parameters and body weight
To confirm the efficacy of the drug treatment, we checked several plasma parameters (Table 1). As expected, AM-treated animals had higher T4, TSH and total cholesterol and lower T3 plasma concentrations than either Dron-treated animals or controls (11). Body weight gain during the experiment in the AM-treated animals was lower compared with the Dron-treated group and controls.
Cardiac component-specific TR gene expression
We studied the mRNA expression of TR isoforms α 1, α 2 and β 1 in three parts of the heart, which represent different cardiac components, namely the RA (including the SAN), the LVW (mainly working myocardium) and the apex (contains a large proportion of PVCS). Dron caused a decreased expression of TRα 1 in the RA but had no effect in the LVW or apex. TRα 2 expression was not influenced by Dron. TRβ 1 expression in RA, LVW and apex was decreased by Dron (Fig. 1). AM lowered TRα 1 expression in the RA, but interestingly increased it in the LVW. In the apex, no change was seen in TRα 1, but TRα 2 increased as a result of AM (Fig. 1). TRβ 1 expression was decreased by AM in all the three components (Fig. 1).
TR-regulated cardiac genes
The same parts of the rat heart were also used to quantify mRNA expression by PCR of a number of T3-dependent genes after AM or Dron treatment, in parallel with visualisation using in situ hybridisation. From the latter experiments, it appears that in the control animals, SERCA2a and α MHC are expressed throughout the heart. ANF is expressed in the atria, apex and PVCS (Figs 3 and 4). Although α MHC is expressed throughout the heart, β MHC is found only in the PVCS. HCN4 showed positive staining only in the SAN.
Dron treatment caused a decrease in α MHC expression in the cardiac apex and shows a trend towards decreased ANF expression in the LVW (Fig. 2). None of the other genes studied were affected by Dron treatment. This is reflected in the in situ hybridisation results as shown in Fig. 3. SERCA2a expression in the RA showed a trend towards a decrease due to AM treatment (P < 0.1). AM increased ANF expression in the apex (Figs 3 and 4). Furthermore, it caused a reciprocal regulation of α MHC and β MHC in this component; α MHC showed a trend towards a decrease in the RA (P < 0.1) and decreased in the apex, whereas β MHC increased in both the components. No difference between the effect of AM and Dron on α MHC expression in the apex was observed. The same observations can be made looking at the in situ hybridisation data (Fig. 3). We did not observe any significant differences in the expression of HCN4 in the RA after AM or Dron treatment (mRNA data not shown; Fig. 4).
Discussion
Here, we study the expression of TH-dependent genes and TRs in relation to certain TH antagonistic effects of the class III anti-arrhythmic drugs AM and Dron. In an earlier paper, we characterised our animal model (11), and the changes in TH parameters seen in this study are essentially the same as in our former one. Furthermore, we showed in our earlier study that both AM and Dron decreased the heart rate and significantly increased the QTc interval (11). We now analyse the mRNA levels, by both in situ hybridisation and quantitative PCR, of a number of well-known T3-dependent genes as well as the levels of the TR isoforms α 1, α 2 and β 1 in the three different components of the rat heart, namely the RA, the LVW and the apex. Since we did not find any major discrepancies between the mRNA and protein levels of the TR isoforms in an earlier paper (21) using hyper- and hypothyroid mice, we concentrate on the mRNA levels of the TR isoforms in the present study.
In the present study, we observe that TRβ 1 is down-regulated by AM and Dron in all the heart components tested. This is probably due to a direct effect of the inhibition by these compounds of TRα 1 (11). Indeed, Sadow et al. (22) suggested that TRα 1 also has a major role in cardiac regulation of both itself and TRβ 1. We found a decreased expression of TRα 1 in the RA, which contains the pacemaking components SAN and AVN due to both Dron and AM, which in case of AM has been shown before (23). The similarity of the effects of AM and Dron on TR isoform expression matches their ability to inhibit TRα 1, the isoform determining cardiac rhythm (3, 4). The down-regulation of TRα 1 itself could be a result of more complicated mechanisms involving TRα 1, TRβ 1 and/or other (component-specific) factors (22). The latter suggestion is supported by our observation that TRα 1 is regulated in a component-and compound-specific manner. For instance, the effect of AM on the expression of TRα 1 in the LVW differs from that of Dron. In this component, TRα 1 is up-regulated by AM, which may signify a compensatory mechanism for the inhibition of T3 action due to the drug. Interestingly, the effects of AM on heart rate and contractility resemble those of the euthyroid TRβ 1 knock-in mouse (24) and correlates with AM’s ability to inhibit both TRα 1 and TRβ 1.
The ability of AM and Dron to differentially inhibit TRα 1 and TRβ 1 is reflected in their effects on TR-regulated cardiac gene expression. We could not find changes in the expression of HCN4 in the RA despite the bradycardia in the AM-treated animals (8). The bradycardia could, however, be explained by the non-genomic effects of AM on β-adrenoceptor density (25).
As expected, AM showed a trend to suppress the expression of the TRα 1-dependent SERCA2a. In addition, α MHC shows a trend of being down-regulated in the RA and it is decreased in the apex by AM but not in the LVW, correlating with the up-regulation of TRα 1 in that compartment. Dron caused down-regulation of the TRα 1-dependent α MHC in the apex, which tallies with earlier reports showing that Dron changes α MHC expression but not β MHC and SERCA2a (6). The differences between Dron and AM could be due to AM’s additional inhibition of TRβ 1.
An interesting finding is that AM, but not Dron, causes an up-regulation of β MHC and ANF. Since AM antagonises both TRα 1 and TRβ 1, our results support the earlier hypothesis that TRβ 1 has an important role for β MHC regulation (7). Furthermore, ANF was up-regulated specifically in the apex, subendocardial and pericoronarial cardiomyocytes, which form the PVCS, thus suggesting that TRβ 1 may have a specific role there. The induction of β MHC and ANF as a result of AM treatment is reminiscent of the induction of these genes after heart failure and could indicate foetal reprogramming, as has been suggested by Kinugawa et al. (26).
Taken together, our results indicate that AM and Dron have similar effects on the expression of TR isoforms in the RA, which could partly contribute to their ability to decrease heart rate. On the other hand, the more profound effect of AM appears on TR- and T3-dependent gene expression in the left ventricle suggests foetal reprogramming.
Acknowledgements
We thank J Daalhuisen for his help with the animal experiments.
Plasma parameters and body weight (BW).
| Control | Dron | AM | ANOVA (P) | |
|---|---|---|---|---|
| Values are represented as mean ± s.d. *P < 0.01 versus controls. | ||||
| TSH (ng/ml) | 2.11 ± 0.80 | 1.45 ± 0.75 | 6.70 ± 3.39* | < 0.0001 |
| T4 (nmol/l) | 72 ± 10 | 68 ± 14 | 150 ± 21* | < 0.0001 |
| T3 (nmol/l) | 1.21 ± 0.13 | 1.09 ± 0.19 | 0.78 ± 0.11* | < 0.0001 |
| Total cholestrol (mmol/l) | 1.94 ± 0.26 | 1.95 ± 0.25 | 2.89 ± 0.53* | < 0.0001 |
| Baseline BW (g) | 287 ± 9 | 295 ± 9 | 288 ± 7 | N.S. |
| Δ BW (g) | 64 ± 13 | 58 ± 7 | 41 ± 11* | < 0.0001 |
Expression of the TR isoforms α 1, α 2 and β 1 in different cardiac components. The mRNA values of control, AM- and Dron-treated rats are corrected for GAPDH and presented as mean ± s.d. *P < 0.05, **P < 0.01 and ***P < 0.001 versus controls.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Expression of the TR isoforms α 1, α 2 and β 1 in different cardiac components. The mRNA values of control, AM- and Dron-treated rats are corrected for GAPDH and presented as mean ± s.d. *P < 0.05, **P < 0.01 and ***P < 0.001 versus controls.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Expression of the TR isoforms α 1, α 2 and β 1 in different cardiac components. The mRNA values of control, AM- and Dron-treated rats are corrected for GAPDH and presented as mean ± s.d. *P < 0.05, **P < 0.01 and ***P < 0.001 versus controls.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Expression of thyroid hormone-regulated genes in components of the rat heart. α MHC, β MHC, SERCA2a, HCN4 and ANF were measured in mRNA derived from different cardiac components of control, AM- and Dron-treated rats. Values are corrected for GAPDH and presented as mean ± s.d. #P < 0.1, *P < 0.05, **P < 0.02 and ***P < 0.01 versus controls.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Expression of thyroid hormone-regulated genes in components of the rat heart. α MHC, β MHC, SERCA2a, HCN4 and ANF were measured in mRNA derived from different cardiac components of control, AM- and Dron-treated rats. Values are corrected for GAPDH and presented as mean ± s.d. #P < 0.1, *P < 0.05, **P < 0.02 and ***P < 0.01 versus controls.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Expression of thyroid hormone-regulated genes in components of the rat heart. α MHC, β MHC, SERCA2a, HCN4 and ANF were measured in mRNA derived from different cardiac components of control, AM- and Dron-treated rats. Values are corrected for GAPDH and presented as mean ± s.d. #P < 0.1, *P < 0.05, **P < 0.02 and ***P < 0.01 versus controls.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Cardiac mRNA expression of thyroid hormone-dependent genes. Overview of the left ventricle of control rats (left), Dron-treated (middle) and AM-treated (right) rats, stained with a sequence-specific, antisense probes, against ANF (first row), α MHC (second row), β MHC (third row) and SERCA2a (fourth row). LWV, left ventricular wall; A, apex. All images are oriented in the same direction.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Cardiac mRNA expression of thyroid hormone-dependent genes. Overview of the left ventricle of control rats (left), Dron-treated (middle) and AM-treated (right) rats, stained with a sequence-specific, antisense probes, against ANF (first row), α MHC (second row), β MHC (third row) and SERCA2a (fourth row). LWV, left ventricular wall; A, apex. All images are oriented in the same direction.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Cardiac mRNA expression of thyroid hormone-dependent genes. Overview of the left ventricle of control rats (left), Dron-treated (middle) and AM-treated (right) rats, stained with a sequence-specific, antisense probes, against ANF (first row), α MHC (second row), β MHC (third row) and SERCA2a (fourth row). LWV, left ventricular wall; A, apex. All images are oriented in the same direction.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Cardiac mRNA expression of thyroid hormone-dependent genes in the right atrium and SAN. Upper row – overview of the RA and superior vena cava (SVC), stained with an ANF-specific, antisense probe, reveals ANF expression throughout RA and SCV (positive staining is in blue). The SAN is indicated by an arrow. Middle row – higher magnification shows similar sizes of the SAN between control animals (left), Dron-treated (middle) and AM-treated animals (right). The SAN is indicated by an arrow. Bottom row – HCN4 is expressed in the SAN of the animals of all groups. The SAN is indicated by an arrow.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Cardiac mRNA expression of thyroid hormone-dependent genes in the right atrium and SAN. Upper row – overview of the RA and superior vena cava (SVC), stained with an ANF-specific, antisense probe, reveals ANF expression throughout RA and SCV (positive staining is in blue). The SAN is indicated by an arrow. Middle row – higher magnification shows similar sizes of the SAN between control animals (left), Dron-treated (middle) and AM-treated animals (right). The SAN is indicated by an arrow. Bottom row – HCN4 is expressed in the SAN of the animals of all groups. The SAN is indicated by an arrow.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
Cardiac mRNA expression of thyroid hormone-dependent genes in the right atrium and SAN. Upper row – overview of the RA and superior vena cava (SVC), stained with an ANF-specific, antisense probe, reveals ANF expression throughout RA and SCV (positive staining is in blue). The SAN is indicated by an arrow. Middle row – higher magnification shows similar sizes of the SAN between control animals (left), Dron-treated (middle) and AM-treated animals (right). The SAN is indicated by an arrow. Bottom row – HCN4 is expressed in the SAN of the animals of all groups. The SAN is indicated by an arrow.
Citation: European Journal of Endocrinology eur j endocrinol 156, 6; 10.1530/EJE-07-0017
References
- 1
Flamant F & Samarut J. Thyroid hormone receptors: lessons from knockout and knock-in mutant mice. Trends in Endocrinology and Metabolism 2003 14 85–90.
- 2↑
Stoykov I, Zandieh-Doulabi B, Moorman AF, Christoffels V, Wiersinga WM & Bakker O. Expression pattern and ontogenesis of thyroid hormone receptor isoforms in the mouse heart. Journal of Endocrinology 2006 189 231–245.
- 3↑
Gloss B, Trost S, Bluhm W, Swanson E, Clark R, Winkfein R, Janzen K, Giles W, Chassande O, Samarut J & Dillmann W. Cardiac ion channel expression and contractile function in mice with deletion of thyroid hormone receptor alpha or beta. Endocrinology 2001 142 544–550.
- 4↑
Wikstrom L, Johansson C, Salto C, Barlow C, Campos BA, Baas F, Forrest D, Thoren P & Vennstrom B. Abnormal heart rate and body temperature in mice lacking thyroid hormone receptor alpha 1. EMBO Journal 1998 17 455–461.
- 5↑
Johansson C, Gothe S, Forrest D, Vennstrom B & Thoren P. Cardiovascular phenotype and temperature control in mice lacking thyroid hormone receptor-beta or both alpha1 and beta. American Journal of Physiology 1999 276 H2006–H2012.
- 6↑
Pantos C, Mourouzis I, Malliopoulou V, Paizis I, Tzeis S, Moraitis P, Sfakianoudis K, Varonos DD & Cokkinos DV. Dronedarone administration prevents body weight gain and increases tolerance of the heart to ischemic stress: a possible involvement of thyroid hormone receptor alpha1. Thyroid 2005 15 16–23.
- 7↑
Kinugawa K, Yonekura K, Ribeiro RC, Eto Y, Aoyagi T, Baxter JD, Camacho SA, Bristow MR, Long CS & Simpson PC. Regulation of thyroid hormone receptor isoforms in physiological and pathological cardiac hypertrophy. Circulation Research 2001 89 591–598.
- 8↑
Singh BN & Vaughan Williams EM. The effect of amiodarone, a new anti-anginal drug, on cardiac muscle. British Journal of Pharmacology 1970 39 657–667.
- 9↑
Bakker O, van Beeren HC & Wiersinga WM. Desethylamiodarone is a noncompetitive inhibitor of the binding of thyroid hormone to the thyroid hormone beta 1-receptor protein. Endocrinology 1994 134 1665–1670.
- 10↑
van Beeren HC, Bakker O & Wiersinga WM. Desethylamiodarone is a competitive inhibitor of the binding of thyroid hormone to the thyroid hormone alpha 1-receptor protein. Molecular and Cellular Endocrinology 1995 112 15–19.
- 11↑
van Beeren HC, Jong WM, Kaptein E, Visser TJ, Bakker O & Wiersinga WM. Dronedarone acts as a selective inhibitor of 3,5,3′-triiodothyronine binding to thyroid hormone receptor-α 1: in vitro and in vivo evidence. Endocrinology 2003 144 552–558.
- 12↑
Hu K, Gaudron P & Ertl G. Effects of high- and low-dose amiodarone on mortality, left ventricular remodeling, and hemodynamics in rats with experimental myocardial infarction. Journal of Cardiovascular Pharmacology 2004 44 627–630.
- 13↑
Pantos C, Mourouzis I, Saranteas T, Paizis I, Xinaris C, Malliopoulou V & Cokkinos DV. Thyroid hormone receptors alpha1 and beta1 are downregulated in the post-infarcted rat heart: consequences on the response to ischaemia-reperfusion. Basic Research in Cardiology 2005 100 422–432.
- 14↑
Wiersinga WM & Chopra IJ. Radioimmunoassay of thyroxine (T4), 3,5,3′-triiodothyronine (T3), 3,3′ ,5′-triiodothyronine (reverse T3, rT3), and 3,3′-diiodothyronine (T2). Methods in Enzymology 1982 84 272–303.
- 15↑
Timmer DC, Bakker O & Wiersinga WM. Triiodothyronine affects the alternative splicing of thyroid hormone receptor alpha mRNA. Journal of Endocrinology 2003 179 217–225.
- 16↑
Moorman AF, Houweling AC, de Boer PA & Christoffels VM. Sensitive nonradioactive detection of mRNA in tissue sections: novel application of the whole-mount in situ hybridization protocol. Journal of Histochemistry and Cytochemistry 2001 49 1–8.
- 17↑
Moorman AF, Vermeulen JL, Koban MU, Schwartz K, Lamers WH & Boheler KR. Patterns of expression of sarcoplasmic reticulum Ca(2 + )-ATPase and phospholamban mRNAs during rat heart development. Circulation Research 1995 76 616–625.
- 18↑
Schiaffino S, Samuel JL, Sassoon D, Lompre AM, Garner I, Marotte F, Buckingham M, Rappaport L & Schwartz K. Nonsynchronous accumulation of alpha-skeletal actin and beta-myosin heavy chain mRNAs during early stages of pressure-overload–induced cardiac hypertrophy demonstrated by in situ hybridization. Circulation Research 1989 64 937–948.
- 19↑
Garcia-Frigola C, Shi Y & Evans SM. Expression of the hyperpolarization-activated cyclic nucleotide-gated cation channel HCN4 during mouse heart development. Gene Expression Patterns 2003 3 777–783.
- 20↑
Zeller R, Bloch KD, Williams BS, Arceci RJ & Seidman CE. Localized expression of the atrial natriuretic factor gene during cardiac embryogenesis. Genes and Development 1987 1 693–698.
- 21↑
Zandieh-Doulabi B, Platvoetter Schiphorst M, Kalsbeek A, Wiersinga WM & Bakker O. Hyper and hypothyroidism change the expression and diurnal variation of thyroid hormone receptor isoforms in rat liver without major changes in their zonal distribution. Molecular and Cellular Endocrinology 2004 219 69–75.
- 22↑
Sadow PM, Chassande O, Koo EK, Gauthier K, Samarut J, Xu J, O’Malley BW & Weiss RE. Regulation of expression of thyroid hormone receptor isoforms and coactivators in liver and heart by thyroid hormone. Molecular and Cellular Endocrinology 2003 203 65–75.
- 23↑
Shahrara S & Drvota V. Thyroid hormone alpha1 and beta1 receptor mRNA are downregulated by amiodarone in mouse myocardium. Journal of Cardiovascular Pharmacology 1999 34 261–267.
- 24↑
Swanson EA, Gloss B, Belke DD, Kaneshige M, Cheng SY & Dillmann WH. Cardiac expression and function of thyroid hormone receptor beta and its PV mutant. Endocrinology 2003 144 4820–4825.
- 25↑
Vassy R, Starzec A, Yin Y, Nicolas P & Perret GY. Amiodarone has exclusively non-genomic action on cardiac beta-adrenoceptor regulation. European Journal of Pharmacology 2000 408 227–232.
- 26↑
Kinugawa K, Minobe WA, Wood WM, Ridgway EC, Baxter JD, Ribeiro RC, Tawadrous MF, Lowes BA, Long CS & Bristow MR. Signaling pathways responsible for fetal gene induction in the failing human heart: evidence for altered thyroid hormone receptor gene expression. Circulation 2001 103 1089–1094.
