The effects of nickel chloride on papillary muscle contractility under normothermic and hypothermic conditions: Comparison of active and hibernating ground squirrels (Urocitellus undulatus) with Wistar rats.

Extracellular Ca2+ plays a pivotal role in the regulation of cardiac contractility under normal and extreme conditions. Here, by using nickel chloride (NiCl2), a non-specific blocker of extracellular Ca2+ influx, we studied the input of extracellular Ca2+ on the regulation of papillary muscle (PM) contractility under normal and hypothermic conditions in ground squirrels (GS), and rats. By measuring isometric force of contraction, we studied how NiCl2 affects force-frequency relationship and the rest effect in PM of these species at 30 °C and 10 °C. We found that at 30 °C 1.5 mM NiCl2 significantly reduced force of contraction across entire frequency range in active GS and rats, whereas in hibernating GS force of contraction was reduced at low and high frequency range. Additionally, NiCl2 evoked spontaneous contractility in rats but not GS PM. The rest effect was significantly reduced by NiCl2 for active GS and rats but not hibernating GS. At 10 °C, NiCl2 fully reduced contractility in active GS and, to a lesser extent, in rats, whereas in hibernating GS it was significant only at 0.3 Hz. The rest effect was significantly reduced by NiCl2 in both active and hibernating GS, whereas it was unmasked in rats that had high contractility under hypothermic conditions in control. Our results show a significant contribution of extracellular Ca2+ to myocardial contractility in GS not only in active but also in hibernating states, especially under hypothermic conditions, whereas limitation of extracellular Ca2+ influx in rats under hypothermia can play protective role for myocardial contractility.

A geometry-based finite element tool for evaluating mitral valve biomechanics.

Mitral valve function depends on its complex geometry and tissue health, with alterations in shape and tissue response affecting the long-term restorarion of function. Previous computational frameworks for biomechanical assessment are mostly based on patient-specific geometries; however, these are not flexible enough to yield a variety of models and assess mitral closure for individually tuned morphological parameters or material property representations. This study details the finite element approach implemented in our previously developed toolbox to assess mitral valve biomechanics and showcases its flexibility through the generation and biomechanical evaluation of different models. A healthy valve geometry was generated and its computational predictions for biomechanics validated against data in the literature. Moreover, two mitral valve models including geometric alterations associated with disease were generated and analysed. The healthy mitral valve model yielded biomechanical predictions in terms of valve closure dynamics, leaflet stresses and papillary muscle and chordae forces comparable to previous computational and experimental studies. Mitral valve function was compromised in geometries representing disease, expressed by the presence of regurgitating areas, elevated stress on the leaflets and unbalanced subvalvular apparatus forces. This showcases the flexibility of the toolbox concerning the generation of a range of mitral valve models with varying geometric definitions and material properties and the evaluation of their biomechanics.

Fluid-structure interaction and structural simulation of high acceleration effects on surgical repaired human mitral valve biomechanics.

Mitral valve dynamics depend on force stability in the mitral leaflets, the mitral annulus, the chordae tendineae, and the papillary muscles. In chordal rupture conditions, the proper function of the valve disrupts, causing mitral regurgitation, the most prevalent valvular disease. In this study, Structural and FSI frameworks were employed to study valve dynamics in healthy, pathologic, and repaired states. Anisotropic, non-linear, hyper-elastic material properties applied to tissues of the valve while the first-order Ogden model reflected the best compatibility with the empirical data. Hemodynamic blood pressure of the cardiovascular system is applied on the leaflets as uniform loads varying by time, and exposure to high acceleration loads imposed on models. Immersed boundary method used for simulation of fluid in a cardiac cycle. In comparison between healthy and pathologic models, stress values and chordal tensions are increased, by nearly threefold and twofold, respectively. Stress concentration on leaflets is reduced by 75% after performing a successful surgical repair on the pathological model. Crash acceleration loads led to more significant stress and chordae tension on models, by 27% and 23%, respectively. It is concluded that a more sophisticated model could lead to a better understanding of human heart valve biomechanics in various conditions. If a preoperative plan is developed based on these modeling methods, the requirement for multiple successive repairs would be eliminated, operative times are shortened, and patient outcomes are improved.

An unusual origin of a papillary muscle of the right ventricle.

Knowledge of anatomical variations of the heart are important to cardiac surgeons, cardiologists, and radiologist. During routine dissection of a 77-year-old male cadaver, we observed an unusual origin of a papillary muscle of the right ventricle arising from the atrioventricular aspect of the moderator band. This papillary muscle was 6.7mm long and 2.6mm wide. It gave rise to two chordae tendineae: one to the inferior (posterior) papillary muscle of the right ventricle and one directly to the inferior (posterior) leaflet of the tricuspid valve. Variants of the internal anatomy of the heart as exemplified in the present case report should be born in mind during image interpretation and invasive procedures of the right ventricle of the heart.

Contractility detection of isolated mouse papillary muscle using myotronic Myostation-Intact device.

BACKGROUND: To understand the relationship between myocardial contractility and external stimuli, detecting ex vivo myocardial contractility is necessary. METHODS: We elaborated a method for contractility detection of isolated C57 mouse papillary muscle using Myostation-Intact system under different frequencies, voltages, and calcium concentrations. RESULTS: The results indicated that the basal contractility of the papillary muscle was 0.27 ± 0.03 mN at 10 V, 500-ms pulse duration, and 1 Hz. From 0.1 to 1.0 Hz, contractility decreased with an increase in frequency (0.45 ± 0.11-0.10 ± 0.02 mN). The voltage-initiated muscle contractility varied from 3 to 6 V, and the contractility gradually increased as the voltage increased from 6 to 10 V (0.14 ± 0.02-0.28 ± 0.03 mN). Moreover, the muscle contractility increased when the calcium concentration was increased from 1.5 to 3 mM (0.45 ± 0.17-1.11 ± 0.05 mN); however, the contractility stopped increasing even when the concentration was increased to 7.5 mM (1.02 ± 0.23 mN). CONCLUSIONS: Our method guaranteed the survivability of papillary muscle ex vivo and provided instructions for Myostation-Intact users for isolated muscle contractility investigations.

Effects of Hyperthyroidism on Contractility and Na+/Ca2+ Exchanger Activity in the Isolated Papillary Muscle of Rats

Abstract Background: Hyperthyroidism (Hy) is an endocrine disorder, in which the thyroid hormones markedly alter the cardiac function. Increased myocardial contractility and cardiac output, improvement in diastolic relaxation, changes in electrical activity, increments in ventricular mass, and arrhythmias have been reported. However, the influences of thyroid hormones upon molecular mechanisms of cardiac functions have not yet been fully understood. Objectives: To evaluate changes in cardiac contractile parameters and the Na+/Ca2+ exchanger (NCX) function in induced hyperthyroid rats. Methods: Hy was induced by intraperitoneal injections of T3 (15 μg/100 g) for 10 days. Contractile parameters and NCX function were evaluated in the isolated papillary muscle. Data normality was confirmed by the Shapiro-Wilk test. The comparison between groups was performed through an unpaired Student's t-test. Results are expressed as mean ± SD. The accepted significance level was p < 0.05. Results: Our data revealed, in the Hy group, an increase of 30.98% in the maximum speed of diastolic relaxation (-284.64 ± 70.70 vs. -217.31 ± 40.30 mN/mm2/sec (p = 0.027)) and a boost of 149% in the NCX function in late phase of relaxation (20.17 ± 7.90 vs. 50.22 ± 11.94 minutes (p = 0.002)), with no changes in the maximum twitch force (p = 0.605) or maximum speed of systolic contraction (p = 0.208) when compared to the control. Conclusion: The improvement in relaxation parameters is hypothetically attributed to an increase in Sarco-Endoplasmic Reticulum Ca2+ATPase isoform 2 (SERCA2) expression and an increased calcium flow through L-type channels that boosted the NCX function.

Effects of Cardiotoxins from Naja oxiana Cobra Venom on Rat Heart Muscle and Aorta: A Comparative Study of Toxin-Induced Contraction Mechanisms.

Cardiotoxins (CaTxs) are a group of snake toxins that affect the cardiovascular system (CVS). Two types (S and P) of CaTxs are known, but the exact differences in the effects of these types on CVS have not been thoroughly studied. We investigated cellular mechanisms of action on CVS for Naja oxiana cobra CaTxs CTX-1 (S-type) and CTX-2 (P-type) focusing on the papillary muscle (PM) contractility and contraction of aortic rings (AR) supplemented by pharmacological analysis. It was found that CTX-1 and CTX-2 exerted dose-dependent effects manifested in PM contracture and AR contraction. CTX-2 impaired functions of PM and AR more strongly than CTX-1. Effects of CaTxs on PM were significantly reduced by nifedipine, an L-type Ca2+ channel blocker, and by KB-R7943, an inhibitor of reverse-mode Na+/Ca2+ exchange. Furthermore, 2-aminoethoxydiphenyl borate, an inhibitor of store-operated calcium entry, partially restored PM contractility damaged by CaTxs. The CaTx influence on AR contracture was significantly reduced by nifedipine and KB-R7943. The involvement of reverse-mode Na+/Ca2+ exchange in the effect of CaTxs on the rat aorta was shown for the first time. The results obtained indicate that CaTx effects on CVS are mainly associated with disturbance of transporting systems responsible for the Ca2+ influx.

Preparation of Neonatal Rat Papillary Muscles for Contractile Studies.

Isolated cardiac tissue allows investigators to study mechanisms underlying normal and pathological conditions, which would otherwise be difficult or impossible to perform in vivo. In contrast to ventricular muscle strip preparations, papillary muscles can be prepared without severely damaging the muscle tissue. In this preparation, the isolated papillary muscle is fixed in an environmentally controlled organ bath chamber and electrically stimulated. The evoked twitch force is recorded using a pressure transducer, and parameters such as twitch force amplitude and twitch kinetics are analyzed. A variety of experimental protocols can be performed to investigate the calcium- and frequency-dependent contractility as well as dose-response curves of contractile agents, as well as simulation of pathologic conditions such as acute cardiac ischemia. Mouse papillary muscle preparations have long been the mainstay for studying interactions between intracellular calcium regulation and contractile responses under a number of simulated pathophysiological conditions. These studies are often used to complement in vitro studies performed using isolated neonatal rat cardiac myocytes. In this procedure, we describe how neonatal rat papillary muscles can also be prepared for use in contractile studies.

Mesenteric Lymph Drainage Improves Cardiac Papillary Contractility and Calcium Sensitivity in Rats with Hemorrhagic Shock.

BACKGROUND: Myocardial dysfunction is an important adverse factor of hemorrhagic shock that induces refractory hypotension, and post-hemorrhagic shock mesenteric lymph (PHSML) return is involved in this adverse effect. This study investigated whether mesenteric lymph drainage (MLD) improves PHSML return-induced cardiac contractile dysfunction via the restoration of cardiomyocyte calcium sensitivity. MATERIALS AND METHODS: A hemorrhage shock model was established by using a controlled hemorrhage through the femoral artery that maintained a mean arterial pressure of 40 ± 2 mmHg for 3 h. MLD and mesenteric lymph duct ligation (MLDL) were performed from 1 to 3 h during hypotension. The papillary muscles of the heart were collected for measurement of calmodulin expression and for determining contractile responses to either isoprenaline or calcium. RESULTS: The results showed that either MLD or MLDL reversed the hemorrhagic shock-induced downregulation of calmodulin expression, a marker protein of cardiomyocyte calcium sensitization, in papillary muscles. MLD also improved the decreased contractile response and ±df/dt of the papillary muscle strip to gradient isoprenaline or calcium caused by hemorrhagic shock. CONCLUSION: These findings indicate that increased cardiac contractibility may be associated with the restoration of calcium sensitivity produced by PHSML drainage.

Contribution of ATP-Mediated Positive Feedback to Sympathetic Nerve-Induced Positive Inotropy in Guinea Pig Ventricular Myocardium.

The functional role of ATP released from sympathetic nerve terminals was examined in isolated guinea pig ventricular papillary muscles. The contractile force of papillary muscles was increased by field electrical stimulation of sympathetic nerve endings. This increase was attenuated by pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) or suramin, blockers of the P2X receptor, and was abolished by propranolol and prazosin. PPADS, suramin, and ATP affected neither the basal contractile force nor the positive inotropic effect of noradrenaline. These results provide functional evidence that ATP released from sympathetic nerve terminals enhances noradrenaline release and contributes to sympathetic nerve-induced inotropy.

Functional Grading of a Transversely Isotropic Hyperelastic Model with Applications in Modeling Tricuspid and Mitral Valve Transition Regions.

Surgical simulators and injury-prediction human models require a combination of representative tissue geometry and accurate tissue material properties to predict realistic tool-tissue interaction forces and injury mechanisms, respectively. While biological tissues have been individually characterized, the transition regions between tissues have received limited research attention, potentially resulting in inaccuracies within simulations. In this work, an approach to characterize the transition regions in transversely isotropic (TI) soft tissues using functionally graded material (FGM) modeling is presented. The effect of nonlinearities and multi-regime nature of the TI model on the functional grading process is discussed. The proposed approach has been implemented to characterize the transition regions in the leaflet (LL), chordae tendinae (CT) and the papillary muscle (PM) of porcine tricuspid valve (TV) and mitral valve (MV). The FGM model is informed using high resolution morphological measurements of the collagen fiber orientation and tissue composition in the transition regions, and deformation characteristics predicted by the FGM model are numerically validated to experimental data using X-ray diffraction imaging. The results indicate feasibility of using the FGM approach in modeling soft-tissue transitions and has implications in improving physical representation of tissue deformation throughout the body using a scalable version of the proposed approach.

Adjustments in ß-Adrenergic Signaling Contribute to the Amelioration of Cardiac Dysfunction by Exercise Training in Supravalvular Aortic Stenosis.

BACKGROUND/AIMS: Aortic stenosis-induced chronic pressure overload leads to cardiac dysfunction and congestive heart failure. The pathophysiological mechanisms of the myocardial impairment are multifactorial and include maladaptive ß-adrenergic signaling. Exercise training (ET) has been used as a non-pharmacological therapy for heart failure management. The present study tested the hypothesis that exercise training attenuates diastolic dysfunction through ß-adrenergic signaling preservation. METHODS: Wistar rats were submitted to ascending aortic stenosis (AS) surgery, and after 18 weeks, a moderate aerobic exercise training protocol was performed for ten weeks. RESULTS: ET attenuated diastolic dysfunction, evaluated by echocardiogram and isolated papillary muscle (IPM) assay. Also, ET reduced features of heart failure, cross-sectional cardiomyocyte area, and exercise intolerance, assessed by treadmill exercise testing. The ß2 adrenergic receptor protein expression was increased in AS rats independently of exercise. Interestingly, ET restored the protein levels of phosphorylated phospholamban at Serine 16 and preserved the ß-adrenergic receptor responsiveness as visualized by the lower myocardial compliance decline and time to 50% tension development and relaxation during ß-adrenergic stimulation in the IPM than untrained rats. Additionally, AS rats presented higher levels of TNFα and iNOS, which were attenuated by ET. CONCLUSION: Moderate ET improves exercise tolerance, reduces heart failure features, and attenuates diastolic dysfunction. In the myocardium, ET decreases the cross-sectional area of the cardiomyocyte and preserves the ß-adrenergic responsiveness, which reveals that the adjustments in ß-adrenergic signaling contribute to the amelioration of cardiac dysfunction by mild exercise training in aortic stenosis rats.

The cardiac work-loop technique: An in vitro model for identifying and profiling drug-induced changes in inotropy using rat papillary muscles.

The cardiac work-loop technique closely mimics the intrinsic in vivo movement and characteristics of cardiac muscle function. In this study, six known inotropes were profiled using the work-loop technique to evaluate the potential of this method to predict inotropy. Papillary muscles from male Sprague-Dawley rats were mounted onto an organ bath perfused with Krebs-Henseleit buffer. Following optimisation, work-loop contractions were performed that included an initial stabilisation period followed by vehicle control or drug administration. Six known inotropes were tested: digoxin, dobutamine, isoprenaline, flecainide, verapamil and atenolol. Muscle performance was evaluated by calculating power output during work-loop contraction. Digoxin, dobutamine and isoprenaline caused a significant increase in power output of muscles when compared to vehicle control. Flecainide, verapamil and atenolol significantly reduced power output of muscles. These changes in power output were reflected in alterations in work loop shapes. This is the first study in which changes in work-loop shape detailing for example the activation, shortening or passive re-lengthening have been linked to the mechanism of action of a compound. This study has demonstrated that the work-loop technique can provide an important novel method with which to assess detailed mechanisms of drug-induced effects on cardiac muscle contractility.

Mechanics of Porcine Heart Valves' Strut Chordae Tendineae Investigated as a Leaflet-Chordae-Papillary Muscle Entity.

Proper blood flow through the atrioventricular heart valves (AHVs) relies on the holistic function of the valve and subvalvular structures, and a failure of any component can lead to life-threatening heart disease. A comprehension of the mechanical characteristics of healthy valvular components is necessary for the refinement of heart valve computational models. In previous studies, the chordae tendineae have been mechanically characterized as individual structures, usually in a clamping-based approach, which may not accurately reflect the in vivo chordal interactions with the leaflet insertion and papillary muscles. In this study, we performed uniaxial mechanical testing of strut chordae tendineae of the AHVs under a unique tine-based leaflet-chordae-papillary muscle testing to observe the chordae mechanics while preserving the subvalvular component interactions. Results of this study provided insight to the disparity of chordae tissue stress-stretch responses between the mitral valve (MV) and the tricuspid valve (TV) under their respective emulated physiological loading. Specifically, strut chordae tendineae of the MV anterior leaflet had peak stretches of 1.09-1.16, while peak stretches of 1.08-1.11 were found for the TV anterior leaflet strut chordae. Constitutive parameters were also derived for the chordae tissue specimens using an Ogden model, which is useful for AHV computational model refinement. Results of this study are beneficial to the eventual improvement of treatment methods for valvular disease.

Perioperative changes of the slope in the preload recruitable stroke work relationship by a single-beat technique after mitral valve surgery in functional mitral regurgitation with non-ischemic dilated cardiomyopathy.

OBJECTIVES: The slope in the preload recruitable stroke work relationship is a highly linear, load-insensitive contractile parameter. However, the perioperative change of the slope has not been reported before. We examined the perioperative slope from a steady-state single beat in patients with functional mitral regurgitation and assessed the correlation with brain natriuretic peptide (BNP) levels. METHODS: The study included 16 patients with non-ischemic dilated cardiomyopathy and refractory heart failure: 10 patients underwent mitral valve plasty and left ventricular plasty (MVP + LVP group) and 6 patients who underwent mitral valve replacement and papillary muscle tugging approximation (MVR + PMTA group). The left ventricular ejection fraction was assessed by the modified Simpson method; the slope was assessed by the single-beat technique using transthoracic echocardiography. BNP levels were measured by chemiluminescent immunoassay. RESULTS: The left ventricular ejection fraction and slope did not significantly change from pre- to early post-surgery in the MVP + LVP group. Both the left ventricular ejection fraction and slope significantly increased 6 months after surgery in the MVR + PMTA group. Postoperative BNP level was low in the MVR + PMTA group. While the postoperative left ventricular ejection fraction did not correlate with BNP levels, the postoperative slope significantly correlated with BNP level after surgery in the MVP + LVP group and in the total functional mitral regurgitation group. CONCLUSIONS: The change of slope was dependent on surgical procedures. In functional mitral regurgitation, the slope may be a more sensitive parameter in reflecting the left ventricular contractile function than the left ventricular ejection fraction.

Differential expressions and functions of phosphodiesterase enzymes in different regions of the rat heart.

Phosphodiesterase enzymes (PDEs) are responsible for the adjustment of cyclic nucleotide levels. Alterations in PDE expressions in different tissues cause conflicts between functional and clinical effects of PDE inhibitors. Therefore, the aim of this study was to investigate the gene and protein expressions and the functional role of PDEs in atrium and ventricle of rat heart. The expressions of PDEs were examined in cardiac intact tissues and enzymatically isolated cells. The effects of PDE1-5 inhibitors (vinpocetine, EHNA, milrinone, rolipram, sildenafil, and IBMX) on basal and isoprenaline-stimulated contractions and sinus rate were recorded in the isolated spontaneously beating right atrium and electrically stimulated left papillary muscles. The mRNA and protein levels of PDEs were significantly different in atrial and ventricular intact tissues and isolated myocytes. Atrial contractions were increased with vinpocetine while suppressed by EHNA, milrinone, rolipram, sildenafil and IBMX. Milrinone, sildenafil and IBMX increased the heart rate whereas vinpocetine caused negative chronotropy. Papillary muscle contractions have been increased only with the vinpocetine and IBMX. Both the expression and the action of PDE-1-5 show atrial and ventricular differences. Therefore, these differences should be taken into account in the experimental or therapeutic approaches of the heart.

Estrogen but not testosterone preserves myofilament function from doxorubicin-induced cardiotoxicity by reducing oxidative modifications.

Here, we aimed to explore sex differences and the impact of sex hormones on cardiac contractile properties in doxorubicin (DOX)-induced cardiotoxicity. Male and female Sprague-Dawley rats were subjected to sham surgery or gonadectomy and then treated or untreated with DOX (2 mg/kg) every other week for 10 wk. Estrogen preserved maximum active tension (Tmax) with DOX exposure, whereas progesterone and testosterone did not. The effects of sex hormones and DOX correlated with both altered myosin heavy chain isoform expression and myofilament protein oxidation, suggesting both as possible mechanisms. However, acute treatment with oxidative stress (H2O2) or a reducing agent (DTT) indicated that the effects on Tmax were mediated by reversible myofilament oxidative modifications and not only changes in myosin heavy chain isoforms. There were also sex differences in the DOX impact on myofilament Ca2+ sensitivity. DOX increased Ca2+ sensitivity in male rats only in the absence of testosterone and in female rats only in the presence of estrogen. Conversely, DOX decreased Ca2+ sensitivity in female rats in the absence of estrogen. In most instances, this mechanism was through altered phosphorylation of troponin I at Ser23/Ser24. However, there was an additional DOX-induced, estrogen-dependent, irreversible (by DTT) mechanism that altered Ca2+ sensitivity. Our data demonstrate sex differences in cardiac contractile responses to chronic DOX treatment. We conclude that estrogen protects against chronic DOX treatment in the heart, preserving myofilament function. NEW & NOTEWORTHY We identified sex differences in cardiotoxic effects of chronic doxorubicin (DOX) exposure on myofilament function. Estrogen, but not testosterone, decreases DOX-induced oxidative modifications on myofilaments to preserve maximum active tension. In rats, DOX exposure increased Ca2+ sensitivity in the presence of estrogen but decreased Ca2+ sensitivity in the absence of estrogen. In male rats, the DOX-induced shift in Ca2+ sensitivity involved troponin I phosphorylation; in female rats, this was through an estrogen-dependent mechanism.

Vasodilating, spasmolytic, inotropic and chronotropic activities of curcuminoids from Curcuma longa in isolated organ preparations of guinea pigs.

Turmeric is a yellowish orange spice, widely used in Asian cuisine and obtained from the rhizome of Curcuma longa. It is a mixture of three curcuminoids namely, curcumin, demethoxycurcumin and bisdemethoxycurcumin. Turmeric has been used as a medicinal substance since ancient times for respiratory and gastrointestinal problems. The aim of the present study was to investigate which curcuminoid contributes to the observed pharmacological activities, all three curcuminoids, the major curcumin metabolite tetrahydrocurcumin, and the non-enzymatic curcumin hydrolysis products ferulic acid, feruloyl methane and vanillin were analyzed for spasmolytic, inotropic and chronotropic activity. Furthermore, their uptake in respective tissue samples was also investigated and correlated with activity. Spasmolytic activity was determined in guinea pig ileum, aorta and pulmonary artery. Inotropic and chronotropic activity was determined on guinea pig papillary muscles and right atrium respectively, while tissue uptake was quantified by using high-performance liquid chromatography (HPLC). All the curcuminoids exhibited significant spasmolytic activity with highest EC50 values for bisdemethoxycurcumin (5.8 ± 0.6 µM) followed by curcumin (12.9 ± 0.7 µM), demethoxycurcumin (16.8 ± 3 µM) and tetrahydrocurcumin (22.9 ± 1.5 µM). While only demethoxycurcumin was able to significantly relax the pulmonary artery with EC50 value of 15.78 ± 0.85 µM. All three curcuminoids showed mild negative chronotropic effects in the isolated right atrium; tetrahydrocurcumin demonstrated no activity. Curcumin and bisdemethoxycurcumin also showed mild positive inotropic effect whereas demethoxycurcumin and tetrahydrocurcumin exhibited weak negative inotropic one. Interestingly, ferulic acid, feruloyl methane and vanillin demonstrated no pharmacologicical activity at all in the various isolated organs. All three curcuminoids and tetrahydrocurcumin showed high uptake into the various tissues where concentrations correlated with pharmacological activity. The results indicate pronounced differences in the in vitro pharmacological activities of curcumin, demethoxycurcumin, bisdemethoxycurcumin and tetrahydrocurcumin which have to be considered in humans after per-oral intake of turmeric powder.

Reactive oxygen species impair the excitation-contraction coupling of papillary muscles after acute exposure to a high copper concentration.

Copper is an essential metal for homeostasis and the functioning of living organisms. We investigated the effects of a high copper concentration on the myocardial mechanics, investigating the reactive oxygen species (ROS) mediated effects. The developed force of papillary muscles was reduced after acute exposure to a high copper concentration and was prevented by co-incubation with tempol, DMSO and catalase. The reuptake of calcium by the sarcoplasmic reticulum was reduced by copper and restored by tempol. The contractile response to Ca2+ was reduced and reversed by antioxidants. The response to the ß-adrenergic agonist decreased after exposure to copper and was restored by tempol and catalase. In addition, the in situ detection showed increased O2·- and OH·. Contractions dependent on the sarcolemmal Ca2+ influx were impaired by copper and restored by antioxidants. Myosin-ATPase activity decreased significantly after copper exposure. In conclusion, a high copper concentration can acutely impair myocardial excitation-contraction coupling, reduce the capacity to generate force, reduce the Ca2+ inflow and its reuptake, and reduce myosin-ATPase activity, and these effects are mediated by the local production of O2·-, OH· and H2O2. These toxicity effects of copper overload suggest that copper is a risk factor for cardiovascular disease.