Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in thyroid status markedly influence cardiac contractile and electrical activity. The predominant route by which triiodothyronine (T3) affects cardiac action is by exerting a direct effect in cardiac myocytes through binding to thyroid hormone nuclear receptor isoforms. In addition, T3 modifies cardiac action by alterations in the vascular system and decreases afterload of the left ventricle by subtle modification related to the sympathetic system. The importance of T3 nuclear receptor function has been further demonstrated by studies in null mutant mice in which thyroid hormone receptor-alpha (TRalpha) and thyroid hormone receptor-beta (TRbeta) or both are deleted. In mice with null mutations of the TRalpha, a markedly decreased heart rate and decreased contractile performance occurs in contrast to mice with deletion of TRbeta that have a normal heart rate and a normal contractile performance under baseline conditions. Thyroid hormone influences on heart rate are exerted by specific ion channel proteins in the sinus node of the left atrium. Some of these ion channels, such as the IF channel, the sodium/calcium exchanger protein, the L-type and T-type calcium channel, and the ryanodine channel are targets for thyroid hormone action. The increased contractile performance induced by T3 is largely mediated by increased expression of the calcium adenosine triphosphatase (ATPase) of the sarcoplasmic reticulum and decreased expression of phospholamban and T3 increases the phosphorylation status of phospholamban. The significant influence that is exerted by thyroid hormone signaling system related to contractile and electrical activity in the heart and the molecular basis for these alterations continues to be clarified.
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PMID:Cellular action of thyroid hormone on the heart. 1216 5

Alterations in thyroid hormone levels have a profound impact on myocardial contractility, speed of relaxation, cardiac output, and heart rate. The mechanisms for these changes include altered expression of several key proteins, involved in the regulation of intracellular calcium homeostasis. Most notably, increases in thyroid hormone and the coordinated increases in cardiac contractile parameters are marked by increases in the levels of the sarcoplasmic reticulum (SR) Ca2+-adenosine triphosphatase (ATPase) and decreases in its inhibitor, phospholamban. These changes at the protein level result in enhanced SR calcium transport and myocyte calcium cycling, leading to increases in the force and rates of contraction as well as relaxation rates at the organ level. However, decreases in thyroid hormone levels are associated with opposite alterations in these two proteins, leading to reduced myocyte calcium handling capacity and lower cardiac contractility. Furthermore, changes in the relative ratio of phospholamban/Ca2+-ATPase correlate with changes in the affinity of the SR Ca2+-transport system and relaxation rates in beating hearts. These findings suggest that thyroid hormone directly regulates SR protein levels and thus, cardiac function.
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PMID:Thyroid hormone regulation of calcium cycling proteins. 1216 6

In animal models the function of the sodium pump (sodium/potassium-adenosine triphosphatase [Na+/K(+)-ATPase]) is enhanced by 3,5,3'-triiodothyronine (T3) and inhibited by the antiarrhythmic agent amio. However, it is still unclear whether the effect of the drug on Na+/K(+)-ATPase depends on the interference with thyroid hormone action. We evaluated the interaction of T3 with amiodarone on Na+/K(+)-ATPase activity and site number in human myocardium. Right atrial slices were cultured with (T3+) and without (T3-) 3 nM T3 in presence and absence of amiodarone at therapeutical dose (1.5 microM). When compared to T3+, T3- preparations showed decreased 3H-ouabain binding (p < 0.004) and lower 20-minute and 45-minute 86Rb-uptake (p < or = 0.004). Amiodarone caused an average 49% reduction of the T3-dependent 3H-ouabain binding and decreased the Western blot signal for the Na+/K(+)-ATPase alpha1 subunit. The drug also inhibited T3-dependent increase in 86Rb-influx at 20 and 45 minutes by 66% and 42%, respectively, without affecting the affinity of the pump for K+. No differences were found in the 3H-ouabain binding and 86Rb-uptake of T3-, T3- amio and T3(+)-amio. In conclusion, T3 stimulates the Na+/K(+)-ATPase in human atrial myocardium by increasing the number of ouabain-binding sites, whereas amiodarone decreases the sodium pump function secondarily to the antagonism with thyroid hormone.
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PMID:Amiodarone inhibits the 3,5,3'-triiodothyronine-dependent increase of sodium/potassium adenosine triphosphatase activity and concentration in human atrial myocardial tissue. 1530 37

Hypothyroid heart displays a phenotype of cardioprotection against ischemia and this study investigated whether administration of dronedarone, an amiodarone-like compound that has been shown to preferentially antagonize thyroid hormone binding to thyroid hormone receptor alpha1 (TRalpha1), results in a similar effect. Dronedarone was given in Wistar rats (90 mg/kg, once daily (od) for 2 weeks) (DRON), while untreated animals served as controls (CONT). Hypothyroidism (HYPO) was induced by propylthiouracil administration. Isolated rat hearts were perfused in Langendorff mode and subjected to 20 minutes of zero-flow global ischemia (I) followed by 45 minutes of reperfusion (R). 3,5,3' Triiodothyronine remained unchanged while body weight and food intake were reduced. alpha-Myosin heavy chain (alpha-MHC) decreased in DRON while beta-myosin heavy chain (beta-MHC) and sarcoplasmic reticulum Ca2+ adenosine triphosphatase (ATPase) expression (SERCA) was similar to CONT. In HYPO, alpha-MHC and SERCA were decreased while beta-MHC was increased. Myocardial glycogen content was increased in both DRON and HYPO. In DRON, resting heart rate and contractility were reduced and ischemic contracture was significantly suppressed while postischemic left ventricular end-diastolic pressure and lactate dehydrogenase release (IU/L min) after I/R were significantly decreased. In conclusion, dronedarone treatment results in cardioprotection by selectively mimicking hypothyroidism. This is accompanied by a reduction in body weight because of the suppression of food intake. TRs might prove novel pharmacologic targets for the treatment of cardiovascular illnesses.
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PMID:Dronedarone administration prevents body weight gain and increases tolerance of the heart to ischemic stress: a possible involvement of thyroid hormone receptor alpha1. 1568 16

Thyroid hormone receptors (TRs) are ligand-regulated transcription factors that bind to thyroid hormone response elements of target genes. Upon ligand binding, they recruit coactivator complexes that increase histone acetylation and recruit RNA polymerase II (Pol II) to activate transcription. Recent studies suggest that nuclear receptors and coactivators may have temporal recruitment patterns on hormone response elements, yet little is known about the nature of the patterns at multiple endogenous target genes. We thus performed chromatin immunoprecipitation assays to investigate coactivator recruitment and histone acetylation patterns on the thyroid hormone response elements of four endogenous target genes (GH, sarcoplasmic endoplasmic reticulum calcium-adenosine triphosphatase, phosphoenolpyruvate carboxykinase, and cholesterol 7alpha-hydroxylase) in a rat pituitary cell line that expresses TRs. We found that TRbeta, several associated coactivators (steroid receptor coactivator-1, glucocorticoid receptor interacting protein-1, and TR-associated protein 220), and RNA Pol II were rapidly recruited to thyroid hormone response elements as early as 15 min after T3 addition. When the four target genes were compared, we observed differences in the types and temporal patterns of recruited coactivators and histone acetylation. Interestingly, the temporal pattern of RNA Pol II was similar for three genes studied. Our findings suggest that thyroid hormone-regulated target genes may have distinct patterns of coactivator recruitment and histone acetylation that may enable highly specific regulation.
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PMID:Thyroid hormone-regulated target genes have distinct patterns of coactivator recruitment and histone acetylation. 1625 15

Administration of chemotherapy during pregnancy may represent a big risk factor for the developing brain, therefore we studied whether the transplacental transport of doxorubicin (DOX) may affect the development of neuroendocrine system. DOX (25 mg/kg; 3 times interaperitoneally/week) was given to pregnant rats during whole gestation period. The disturbances in neuroendocrine functions were investigated at gestation day (GD) 15 and 20 by following the maternal and fetal thyroid hormone levels, fetal nucleotides (ATP, ADP, AMP) levels and adenosine triphosphatase (Na(+), K(+)-ATPase, Ca(2+)-ATPase and Mg(2+)-ATPase) activities in two brain regions, cerebrum and cerebellum. In control group, the levels of maternal and fetal serum thyroxine (T4), triiodothyronine (T3), thyrotropin (TSH), and fetal serum growth hormone (GH) increased from days 15 to 20, whereas in the DOX group, a decrease in maternal and fetal T4, T3 and increase in TSH levels (hypothyroid status) were observed. Also, the levels of fetal GH decreased continuously from GD 15 to 20 with respect to control group. In cerebrum and cerebellum, the levels of fetal nucleotides and the activities of fetal ATPases in control group followed a synchronized course of development. The fetal hypothyroidism due to maternal administration of DOX decreased the levels of nucleotides, ATPases activities, and total adenylate, instead, the adenylate energy charge showed a trend to an increase in both brain regions at all ages tested. These alterations were dose- and age-dependent and this, in turn, may impair the nerve transmission. Finally, DOX may act as neuroendocrine disruptor causing hypothyroidism and fetal brain energetic dysfunction.
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PMID:Gestational doxorubicin alters fetal thyroid-brain axis. 2318 40

Objective: Hypothyroidism is not commonly considered a cause of hyperkalemia. We previously reported that hyperkalemia was observed mainly in elderly patients treated with renin-angiotensin-aldosterone system (RAS) inhibitors when levothyroxine treatment was withdrawn for the thyroidectomized patients with thyroid carcinoma to undergo radioactive iodine treatment. Here, we investigated whether acute hypothyroidism causes hyperkalemia in patients who were not treated with RAS inhibitors. We also investigated factors influencing potassium metabolism in hypothyroid patients. Methods: We conducted a single-center, prospective cohort study of 46 Japanese patients with thyroid carcinoma undergoing levothyroxine withdrawal prior to radioiodine therapy. All patients were normokalemic before levothyroxine withdrawal. Blood samples were analyzed 3 times: before, and at 3 and 4 weeks after levothyroxine withdrawal. We investigated factors that may be associated with the elevation of serum potassium levels from a euthyroid state to a hypothyroid state. Results: None of the patients developed symptomatic hyperkalemia. The mean serum potassium level was significantly higher at 4 weeks after levothyroxine withdrawal compared to baseline. The serum sodium levels, the estimated glomerular filtration rate (eGFR), and the plasma renin activity (PRA) decreased significantly as hypothyroidism advanced. In contrast, the plasma levels of adrenocorticotropic hormone, cortisol, aldosterone, and antidiuretic hormone were not changed, while serum thyroid hormone decreased. At 4 weeks after their levothyroxine withdrawal, the patients' serum potassium values were significantly correlated with the eGFR and the PRA. Conclusion: Acute hypothyroidism can cause a significant increase in the serum potassium level, which may be associated with a decreased eGFR and decreased circulating RAS. Abbreviations: ACTH = adrenocorticotropic hormone; ADH = antidiuretic hormone; ATPase = adenosine triphosphatase; eGFR = estimated glomerular filtration rate; HbA1c = glycated hemoglobin; K+ = potassium; Na+ = sodium; PRA = plasma renin activity; RAS = renin-angiotensin-aldosterone system; T4 = thyroxine; TSH = thyroid-stimulating hormone.
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PMID:RENAL FUNCTION AND PLASMA RENIN ACTIVITY AS POTENTIAL FACTORS CAUSING HYPERKALEMIA IN PATIENTS WITH THYROID CARCINOMA UNDERGOING THYROID HORMONE WITHDRAWAL FOR RADIOACTIVE IODINE THERAPY. 3165


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