Food-grade titanium dioxide and zinc oxide nanoparticles induce toxicity and cardiac damage after oral exposure in rats.

BACKGROUND: Metallic nanoparticles (NPs) are widely used as food additives for human consumption. NPs reach the bloodstream given their small size, getting in contact with all body organs and cells. NPs have adverse effects on the respiratory and intestinal tract; however, few studies have focused on the toxic consequences of orally ingested metallic NPs on the cardiovascular system. Here, the effects of two food-grade additives on the cardiovascular system were analyzed. METHODS: Titanium dioxide labeled as E171 and zinc oxide (ZnO) NPs were orally administered to Wistar rats using an esophageal cannula at 10 mg/kg bw every other day for 90 days. We evaluated cardiac cell morphology and death, expression of apoptotic and autophagic proteins in cardiac mitochondria, mitochondrial dysfunction, and concentration of metals on cardiac tissue. RESULTS: Heart histology showed important morphological changes such as presence of cellular infiltrates, collagen deposition and mitochondrial alterations in hearts from rats exposed to E171 and ZnO NPs. Intracellular Cyt-C levels dropped, while TUNEL positive cells increased. No significant changes in the expression of inflammatory cytokines were detected. Both NPs altered mitochondrial function indicating cardiac dysfunction, which was associated with an elevated concentration of calcium. ZnO NPs induced expression of caspases 3 and 9 and two autophagic proteins, LC3B and beclin-1, and had the strongest effect compared to E171. CONCLUSIONS: E171 and ZnO NPs induce adverse cardiovascular effects in rats after 90 days of exposure, thus food intake containing these additives, should be taken into consideration, since they translocate into the bloodstream and cause cardiovascular damage.

Possible implication of estrogenic compounds on heart disease in menopausal women.

Epidemiological studies imply there is a higher risk of cardiovascular disease in menopausal women. Some explanations suggest a lack of estrogens as the cause, but estrogens do not disappear completely and are just transformed into different products called estrogenic degradation metabolites (EDMs). When estrogens are metabolized, reactive oxygen species (ROS) increase, causing DNA damage and increasing oxidative stress. These conditions are associated to neurodegenerative diseases and different types of cancer. However, their effect on the cardiovascular system remains unknown. This paper compares estrogenic metabolite levels in serum from post-menopausal women with cardiovascular risk (CAC>1) and with establish cardiovascular disease (CVD), against levels in healthy women (Ctrl). Sample sera were obtained from the Genetics of Atherosclerotic Disease (GEA) Mexican Study. Serum levels of eleven estrogenic metabolites were quantified by High performance liquid chromatography (HPLC) and oxidative stress markers such as ROS, lipoperoxidation levels (TBARS), total antioxidant capacity (TAC), super oxide dismutase activity (SOD) and cytokine levels were evaluated. 8-hydroxy-2-deoxyguanosine (8-OHdG) was also determined as a marker of nuclear damage.There were significant differences between serum levels of some EDMs in CAC> 1 and CVD vs. serum levels in Ctrl women. Results also revealed an increase in oxidative stress and a diminished capacity to manage oxidative stress. These findings provide an overview, and suggest that some estrogenic metabolites may be associated with an increased risk of CVD in menopausal women. However, additional studies are needed to evaluate the impact of these EDMs directly on cardiovascular function.

PPAR Alpha Activation by Clofibrate Alleviates Ischemia/Reperfusion Injury in Metabolic Syndrome Rats by Decreasing Cardiac Inflammation and Remodeling and by Regulating the Atrial Natriuretic Peptide Compensatory Response.

Metabolic syndrome (MetS) is a cluster of factors that increase the risk of developing diabetes, stroke, and heart failure. The pathophysiology of injury by ischemia/reperfusion (I/R) is highly complex and the inflammatory condition plays an important role by increasing matrix remodeling and cardiac apoptosis. Natriuretic peptides (NPs) are cardiac hormones with numerous beneficial effects mainly mediated by a cell surface receptor named atrial natriuretic peptide receptor (ANPr). Although NPs are powerful clinical markers of cardiac failure, their role in I/R is still controversial. Peroxisome proliferator-activated receptor α agonists exert cardiovascular therapeutic actions; however, their effect on the NPs' signaling pathway has not been extensively studied. Our study provides important insight into the regulation of both ANP and ANPr in the hearts of MetS rats and their association with the inflammatory conditions caused by damage from I/R. Moreover, we show that pre-treatment with clofibrate was able to decrease the inflammatory response that, in turn, decreases myocardial fibrosis, the expression of metalloprotease 2 and apoptosis. Treatment with clofibrate is also associated with a decrease in ANP and ANPr expression.

Characterization of hypotensive and vasorelaxant effects of PHAR-DBH-Me a new cannabinoid receptor agonist.

The effect of PHAR-DBH-Me, a cannabinoid receptor agonist, on different cardiovascular responses in adult male rats was analyzed. The blood pressure was measured directly and indirectly. The coronary flow was measured by Langendorff preparation, and vasomotor responses induced by PHAR-DBH-Me in aortic rings precontracted with phenylephrine (PHEN) were analyzed. The intravenous injection of the compound PHAR-DBH-Me (0.018-185 µg/kg) resulted in decreased blood pressure; maximum effect was observed at the dose of 1,850 µg/kg. A concentration-dependent increase in the coronary flow was observed in a Langendorff preparation. In the aortic rings, with and without endothelium, pre-contracted with PHEN (10-6 M), the addition of PHAR-DBH-Me to the superfusion solution (10-12-10-5 M), produced a vasodilator response, which depends on the concentration and presence of the endothelium. L-NAME inhibited these effects. Addition of CB1 receptor antagonist (AM 251) did not modify the response, while CB2 receptor antagonist (AM630) decreased the potency of relaxation elicited by PHAR-DBH-Me. Indomethacin shifted the curve concentration-response to the left and produced an increase in the magnitude of the maximum endothelium dependent response to this compound. The maximum effect of PHAR-DBH-Me was observed with the concentration of 10-5 M. These results show that PHAR-DBH-Me has a concentration-dependent and endothelium-dependent vasodilator effect through CB2 receptor. This vasodilation is probably mediated by the synthesis/release of NO. On the other hand, it is suggested that PHAR-DBH-Me also induces the release of a vasoconstrictor prostanoid.

Unilateral Ureteral Obstruction for 28 Days in Rats Is Not Associated with Changes in Cardiac Function or Alterations in Mitochondrial Function.

Our work evaluated cardiac function and mitochondrial bioenergetics parameters in hearts from male Wistar rats subjected to the UUO model during 28 days of progression. We measured markers of kidney damage and inflammation in plasma and renal fibrosis by histological analysis and Western blot. Cardiac function was evaluated by echocardiography and proteins involved in cardiac damage by Western blot. Oxygen consumption and transmembrane potential were monitored in cardiac mitochondria using high-resolution respirometry. We also determined the activity of ATP synthase and antioxidant enzymes such as glutathione peroxidase, glutathione reductase, and catalase. Our results show that, although renal dysfunction is established in animals subjected to ureteral obstruction, cardiac function is maintained along with mitochondrial function and antioxidant enzymes activity after 28 days of injury evolution. Our results suggest that renocardiac syndrome might develop but belatedly in obstruction-induced renal damage, opening the opportunity for treatment to prevent this condition.

Autonomous activation of CaMKII exacerbates diastolic calcium leak during beta-adrenergic stimulation in cardiomyocytes of metabolic syndrome rats.

Autonomous Ca2+/calmodulin-dependent protein kinase II (CaMKII) activation induces abnormal diastolic Ca2+ leak, which leads to triggered arrhythmias in a wide range of cardiovascular diseases, including diabetic cardiomyopathy. In hyperglycemia, Ca2+ handling alterations can be aggravated under stress conditions via the ß-adrenergic signaling pathway, which also involves CaMKII activation. However, little is known about intracellular Ca2+ handling disturbances under ß-adrenergic stimulation in cardiomyocytes of the prediabetic metabolic syndrome (MetS) model with obesity, and the participation of CaMKII in these alterations. MetS was induced in male Wistar rats by administering 30 % sucrose in drinking water for 16 weeks. Fluo 3-loaded MetS cardiomyocytes exhibited augmented diastolic Ca2+ leak (in the form of spontaneous Ca2+ waves) under basal conditions and that Ca2+ leakage was exacerbated by isoproterenol (ISO, 100 nM). At the molecular level, [3H]-ryanodine binding and basal phosphorylation of cardiac ryanodine receptor (RyR2) at Ser2814, a CaMKII site, were increased in heart homogenates of MetS rats with no changes in RyR2 expression. These alterations were not further augmented by Isoproterenol. SERCA pump activity was augmented 48 % in MetS hearts before ß-adrenergic stimuli, which is associated to augmented PLN phosphorylation at T17, a target of CaMKII. In MetS hearts. CaMKII auto-phosphorylation (T287) was increased by 80 %. The augmented diastolic Ca2+ leak was prevented by CaMKII inhibition with AIP. In conclusion, CaMKII autonomous activation in cardiomyocytes of MetS rats with central obesity significantly contributes to abnormal diastolic Ca2+ leak, increasing the propensity for ß-adrenergic receptor-driven lethal arrhythmias.

Composite sarcoma of bone with focal rhabdomyosarcoma and lymph node metastasis in an adolescent.

Composite sarcoma of bone is a very rare entity that primarily affects adolescent and young adult patients. It usually combines areas of liposarcoma and osteosarcoma, and up to 60% of cases have metastatic disease at diagnosis. It is a highly aggressive pathology with intrinsic resistance to bone sarcoma conventional treatments. The prognosis is poor, with long-term survival rates not exceeding 30%. We present the case of an adolescent female diagnosed with an aggressive composite sarcoma of bone with rhabdomyosarcoma foci and loco-regional lymph node involvement.

Effects of Oleamide on the Vasomotor Responses in the Rat.

Introduction: Cardiovascular effects of endocannabinoids (eCBs) have generated considerable interest since it has been suggested that the eCB system could become the new pharmacological target, either by blocking its activity or by promoting its effects on several cardiovascular diseases such as hypovolemic and septic shock or hypertension. The purpose of this study was to examine the effects of oleamide on several vasomotor responses in adult rats. Materials and Methods: Blood pressure (BP) was measured both directly and indirectly. Coronary flow was quantified with Langendorf preparation, and the vasomotor responses induced by oleamide were analyzed in the aortic rings. Results: Oleamide induced a decrease in BP, by both direct and indirect methods, which were dose dependent. An increase in coronary flow was observed with Langendorf preparation depending on the dose. Oleamide produced a vasodilator response in aortic rings pre-contracted with phenylephrine (10-5 M), which was concentration and endothelium dependent. This relaxing effect was of minor magnitude than that induced with the same dose on BP. L-NAME did not modify these effects. However, indomethacin induced a shift to the left of the concentration-response curve to oleamide and an increase in the magnitude of maximum vasodilation in rings with endothelium. Oleamide produced the maximal relaxant response at 10-5 M concentration. Conclusions: Oleamide has both in vivo and in vitro vasodilator effects. Vasodilator effects could be mediated by compounds synthesized/released by the endothelium (hyperpolarizing factor) or acting directly on vascular smooth muscle in aortic rings. The TRPV1 and CB1R receptors could mediate these effects. Finally, the results suggest that oleamide probably induces the synthesis/release of a vasoconstrictor prostanoid.

Interaction of Agaric Acid with the Adenine Nucleotide Translocase Induces Mitochondrial Oxidative Stress.

Mitochondrial permeability transition is characterized by the opening of a transmembranal pore that switches membrane permeability from specific to nonspecific. This structure allows the free traffic of ions, metabolites, and water across the mitochondrial inner membrane. The opening of the permeability transition pore is triggered by oxidative stress along with calcium overload. In this work, we explored if oxidative stress is a consequence, rather than an effector of the pore opening, by evaluating the interaction of agaric acid with the adenine nucleotide translocase, a structural component of the permeability transition pore. We found that agaric acid induces transition pore opening, increases the generation of oxygen-derived reactive species, augments the oxidation of unsaturated fatty acids in the membrane, and promotes the detachment of cytochrome c from the inner membrane. The effect of agaric acid was inhibited by the antioxidant tamoxifen in association with decreased binding of the thiol reagent eosin-3 maleimide to the adenine nucleotide translocase. We conclude that agaric acid promotes the opening of the pore, increasing ROS production that exerts oxidative modification of critical thiols in the adenine nucleotide translocase.

Humanización de los cuidados de enfermería ante diversas respuestas producidas por el paciente trasplantado de medula ósea durante la internación y el tratamiento / Humanization of nursing care in response to various responses produced by the bone marrow transplant patient during hospitalization and treatment

OBJETIVO: En este trabajo se abordan los problemas emocionales del paciente: miedo a la muerte y a lo desconocido, ansiedad, incomodidad, estrés, depresión que surgen en respuesta a diversos estimulos como la soledad de la habitación de aislamiento, los ruidos de aparatos médicos, exhaustivas y contínuas exploraciones fisicas durante las cuales el paciente escucha conversaciones sobre él, con terminología médica incomprensible y se toman decisiones sobre su tratamiento de las cuales no se siente partícipe, además del gran sufrimiento por su enfermedad, incomodidad debido al dolor, la falta de motivación y de fuerza fisica por la duración de la enfermedad y la lenta recuperación que lo preocupa. METODOLOGÍA: Se realizó un estudio observacional descriptivo transversal de los 42 pacientes trasplantados en el período desde enero a diciembre del 2018, internados en el Area de Recuperación de Trasplante de Médula Osea del Hospital de Alta Complejidad en Red El Cruce. CONCLUSIONES: Un paciente al que se realiza un trasplante de médula ósea requiere un cuidado especializado de enfermería durante todas las etapas del mismo, con conocimiento y habilidades para anticiparse a todas las complicaciones que puedan surgir. Con esa finalidad se elabora el proceso de atención de enfermería (PAE) con un abordaje holistico y humanizado, donde se incluyen diagnóstico, objetivos, intervenciones y evaluaciones sobre todas las complicaciones, tanto físicas como emocionales.

OBJECTIVE: This research work addresses the emotional problems of the patient: fear of death and the unknown, anxiety, discomfort, stress, depression that arise in response to various stimuli such as the loneliness of the isolation room, the sounds of medical devices, exhaustive and continuous physical examinations during which the patient hears conversations about him, with incomprehensible medical terminology and decisions are made about his treatment of which does not feel participant, in addition to the great suffering for his illness, discomfort due to pain, lack of motivation. METHODS: A cross-sectional descriptive observational study of 42 transplanted patients was performed. In the period january to december of 2019, interned in the Transplant Recovery Area of Bone Marrow of the High Complexity Hospital in Red El Cruce. CONCLUSIONS: A patient who undergoes a bone marrow transplant requires specialized nursing care during all stages of it, with knowledge and skills to anticipate all complications that may arise. For this purpose, the nursing care process is developed with a holistic approach, which includes diagnoses, objectives, interventions and evaluations on all complications, both physical and emotional. And physical strength for the duration of the disease and the slow recovery that worries him.

Mechanisms of Fasting-Mediated Protection against Renal Injury and Fibrosis Development after Ischemic Acute Kidney Injury.

Ischemia-reperfusion injury of the kidney may lead to renal fibrosis through a combination of several mechanisms. We recently demonstrated that fasting protects the rat kidney against oxidative stress and mitochondrial dysfunction in early acute kidney injury, and also against fibrosis development. Here we show that preoperative fasting preserves redox status and mitochondrial homeostasis at the chronic phase of damage after severe ischemia. Also, the protective effect of fasting coincides with the suppression of inflammation and endoplasmic reticulum stress, as well as the down-regulation of the mechanistic target of rapamycin (mTOR) and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathways in the fibrotic kidney. Our results demonstrate that fasting targets multiple pathophysiological mechanisms to prevent renal fibrosis and damage that results after renal ischemia-reperfusion injury.

Clofibrate Treatment Decreases Inflammation and Reverses Myocardial Infarction-Induced Remodelation in a Rodent Experimental Model.

Myocardial infarction (MI) initiates an inflammatory response that promotes both beneficial and deleterious effects. The early response helps the myocardium to remove damaged tissue; however, a prolonged later response brings cardiac remodeling characterized by functional, metabolic, and structural pathological changes. Current pharmacological treatments have failed to reverse ischemic-induced cardiac damage. Therefore, our aim was to study if clofibrate treatment was capable of decreasing inflammation and apoptosis, and reverse ventricular remodeling and MI-induced functional damage. Male Wistar rats were assigned to (1) Sham coronary artery ligation (Sham) or (2) Coronary artery ligation (MI). Seven days post-MI, animals were further divided to receive vehicle (V) or clofibrate (100 mg/kg, C) for 7 days. The expression of IL-6, TNF-α, and inflammatory related molecules ICAM-1, VCAM-1, MMP-2 and -9, nuclear NF-kB, and iNOS, were elevated in MI-V. These inflammatory biomarkers decreased in MI-C. Also, apoptotic proteins (Bax and pBad) were elevated in MI-V, while clofibrate augmented anti-apoptotic proteins (Bcl-2 and 14-3-3ε). Clofibrate also protected MI-induced changes in ultra-structure. The ex vivo evaluation of myocardial functioning showed that left ventricular pressure and mechanical work decreased in infarcted rats; clofibrate treatment raised those parameters to control values. Echocardiogram showed that clofibrate partially reduced LV dilation. In conclusion, clofibrate decreases cardiac remodeling, decreases inflammatory molecules, and partly preserves myocardial diameters.

On the oxidative damage by cadmium to kidney mitochondrial functions.

In the kidney, the accumulation of heavy metals such as Cd2+ produces mitochondrial dysfunctions, i.e., uncoupling of the oxidative phosphorylation, inhibition of the electron transport through the respiratory chain, and collapse of the transmembrane electrical gradient. This derangement may be due to the fact that Cd2+ induces the transition of membrane permeability from selective to nonselective via the opening of a transmembrane pore. In fact, Cd2+ produces this injury through the stimulation of oxygen-derived radical generation, inducing oxidative stress. Several molecules have been used to avoid or even reverse Cd2+-induced mitochondrial injury, for instance, cyclosporin A, resveratrol, dithiocarbamates, and even EDTA. The aim of this study was to explore the possibility that the antioxidant tamoxifen could protect mitochondria from the deleterious effects of Cd2+. Our results indicate that the addition of 1 µmol/L Cd2+ to mitochondria collapsed the transmembrane electrical gradient, induced the release of cytochrome c, and increased both the generation of H2O2 and the oxidative damage to mitochondrial DNA (among other measured parameters). Of interest, these mitochondrial dysfunctions were ameliorated after the addition of tamoxifen.

Calcium Induces Mitochondrial Oxidative Stress Because of its Binding to Adenine Nucleotide Translocase.

Several studies have demonstrated that the mitochondrial membrane switches from selective to non-selective permeability because of its improved matrix Ca2+ accumulation and oxidative stress. This process, known as permeability transition, evokes severe dysfunction in mitochondria through the opening of a non-specific pore, whose chemical nature is still under discussion. There are some proposals regarding the components of the pore structure, e.g., the adenine nucleotide translocase and dimers of the F1 Fo-ATP synthase. Our results reveal that Ca2+ induces oxidative stress, which not only increases lipid peroxidation and ROS generation but also brings about both the collapse of the transmembrane potential and the membrane release of cytochrome c. Additionally, it is shown that Ca2+ increases the binding of the probe eosin-5-maleimide to adenine nucleotide translocase. Interestingly, these effects are diminished after the addition of ADP. It is suggested that pore opening is caused by the binding of Ca2+ to the adenine nucleotide translocase.

Cytidine-5'-Diphosphocholine Protects the Liver From Ischemia/Reperfusion Injury Preserving Mitochondrial Function and Reducing Oxidative Stress.

Cytidine-5'-diphosphocholine (CDP-choline) participates as an intermediary in the synthesis of phosphatidylcholine, an essential component of cellular membranes. Citicoline treatment has shown beneficial effects in cerebral ischemia, but its potential to diminish reperfusion damage in liver has not been explored. In this work, we evaluated the hepatoprotective effect of citicoline and its possible association with inflammatory/oxidative stress and mitochondrial function because they are the main cellular features of reperfusion damage. Ischemia/reperfusion (I/R) in rat livers was performed with the Pringle's maneuver, clamping the 3 elements of the pedicle (hepatic artery, portal vein, and biliary tract) for 30 minutes and then removing the clamp to allow hepatic reperfusion for 60 minutes. The I/R + citicoline group received the compound before I/R. Liver injury was evaluated by measuring aspartate aminotransferase and alanine aminotransferase as well as lactic acid levels in serum; proinflammatory cytokines, proresolving lipid mediators, and nuclear factor kappa B content were determined as indicators of the inflammatory response. Antioxidant effects were evaluated by measuring markers of oxidative stress and antioxidant molecules. Oxygen consumption and the activities of the respiratory chain were used to monitor mitochondrial function. CDP-choline reduced aspartate aminotransferase (AST), alanine aminotransferase (ALT), as well as lactic acid levels in blood samples from reperfused rats. Diminution in tumor necrosis factor alpha (TNF-α) and increase in the proresolving lipid mediator resolvin D1 were also observed in the I/R+citicoline group, in comparison with the I/R group. Oxidative/nitroxidative stress in hepatic mitochondria concurred with deregulation of oxidative phosphorylation, which was associated with the loss of complex III and complex IV activities. In conclusion, CDP-choline attenuates liver damage caused by ischemia and reperfusion by reducing oxidative stress and maintaining mitochondrial function. Liver Transplantation XX XX-XX 2018 AASLD.

CDP-choline circumvents mercury-induced mitochondrial damage and renal dysfunction.

Heavy metal ions are known to produce harmful alterations on kidney function. Specifically, the accumulation of Hg2+ in kidney tissue may induce renal failure. In this work, the protective effect of CDP-choline against the deleterious effects induced by Hg2+ on renal function was studied. CDP-choline administered ip at a dose of 125 mg/kg body weight prevented the damage induced by Hg2+ administration at a dose of 3 mg/kg body weight. The findings indicate that CDP-choline guards mitochondria against Hg2+ -toxicity by preserving their ability to retain matrix content, such as accumulated Ca2+ . This nucleotide also protected mitochondria from Hg2+ -induced loss of the transmembrane electric gradient and from the generation of hydrogen peroxide and membrane TBARS. In addition, CDP-choline avoided the oxidative damage of mtDNA and inhibited the release of the interleukins IL-1 and IL6, recognized as markers of acute inflammatory reaction. After the administration of Hg2+ and CDP, CDP-choline maintained nearly normal levels of renal function and creatinine clearance, as well as blood urea nitrogen (BUN) and serum creatinine.

Tamoxifen inhibits mitochondrial membrane damage caused by disulfiram.

In this work, we studied the protective effects of tamoxifen (TAM) on disulfiram (Dis)-induced mitochondrial membrane insult. The results indicate that TAM circumvents the inner membrane leakiness manifested as Ca2+ release, mitochondrial swelling, and collapse of the transmembrane electric gradient. Furthermore, it was found that TAM prevents inactivation of the mitochondrial enzyme aconitase and detachment of cytochrome c from the inner membrane. Interestingly, TAM also inhibited Dis-promoted generation of hydrogen peroxide. Given that TAM is an antioxidant molecule, it is plausible that its protection may be due to the inhibition of Dis-induced oxidative stress.

Increased calcium leak associated with reduced calsequestrin expression in hyperthyroid cardiomyocytes.

INTRODUCTION: Calcium (Ca2+) leak during cardiac diastole is chiefly mediated by intracellular Ca2+ channel/Ryanodine Receptors. Increased diastolic Ca2+ leak has been proposed as the mechanism underlying the appearance of hereditary arrhythmias. However, little is known about alterations in diastolic Ca2+ leak and the specific roles played by key intracellular Ca2+-handling proteins in hyperthyroidism, a known arrhythmogenic condition. AIM: We sought to determine whether there were modifications in diastolic Ca2+ leak, based on the recording of Ca2+ sparks and Ca2+ waves; we also investigated changes in the expression and activity of key Ca2+ handling proteins, including ryanodine receptors, Sarco-Endoplasmic Reticulum Ca2+ ATPase pump and calsequestrin in isolated left-ventricular cardiomyocytes isolated from hyperthyroid rats. MATERIALS AND METHODS: Electrocardiography (ECG) recordings were performed in control and hyperthyroid rats. Ca2+ sparks, Ca2+ waves, and electrically-stimulated Ca2+ transients were recorded in Fluo-3-loaded cardiomyocytes from both experimental groups using confocal microscopy. In addition, left-ventricular homogenates and Ryanodine Receptor-enriched membrane fractions were prepared for assessing [3H]-ryanodine binding, hydrolytic ATPase activity of SERCA pump and expression levels of key proteins by Western blot, and cDNA for real-time qPCR. RESULTS AND CONCLUSIONS: Extrasystoles were observed in hearts of hyperthyroid rats by ECG recordings. Arrhythmogenic activity, high incidence of Ca2+ waves, and de novo Ca2+ wavelets -in the absence of sarcoplasmic reticulum Ca2+ overload- were recorded in these cardiomyocytes. The exacerbated diastolic Ca2+ leak and arrhythmogenic activities were related to a diminished expression of calsequestrin along with increased SERCA pump activity, which, in effect, promoted a gain-of-function in RyRs without alterations in SR Ca2+ load, RyR expression or its Ca2+ sensitivity.