Fecal metabolomics based on mass spectrometry to investigate the mechanism of qishen granules against isoproterenol-induced chronic heart failure in rats.

Qishen granules, derived from clinical experience formula, has been widely used to improve and treat myocardial ischemic chronic heart failure in China. However, the mechanism of action of Qishen granules in the treatment of chronic heart failure is unclear. This study aimed to discover potential biomarkers of isoproterenol-induced chronic heart failure rats and investigate the potential mechanism of Qishen granules treatment of chronic heart failure. The fecal metabolomics method based on ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry was used to analyze the therapeutic effect and metabolic changes of Qishen granules on chronic heart failure rats. Totally, 17 potential biomarkers were identified, involving bile acid metabolism, fatty acid metabolism, inflammatory response, and amino acid metabolism. For bile acid metabolism, we selected 12 bile acids (two of which were potential biomarkers in nontargeted metabolomics) for quantitative analysis. The quantitative results of bile acids showed that after Qishen granules treatment, the contents of bile acids such as ursodeoxycholic acid and glycodeoxycholic acid were similar to those of health group. This study helps to understand the pathogenesis of isoproterenol-induced chronic heart failure and the therapeutic mechanism of Qishen granules from the perspective of metabolic pathways.

Trace Element Determination and Cardioprotection of Terminalia pallida Fruit Ethanolic Extract in Isoproterenol Induced Myocardial Infarcted Rats by ICP-MS.

The trace elements and minerals in Terminalia pallida fruit ethanolic extract (TpFE) were determined by the instrument inductively coupled plasma-mass spectrometry (ICP-MS), and the cardioprotection of TpFE against isoproterenol (ISO)-administered rats was studied. Rats were pretreated with TpFE (100, 300, and 500 mg/kg bw) for 30 days, with concurrent administration of ISO (85 mg/kg bw) for two consecutive days. The levels of trace elements and minerals in TpFE were below the permitted limits of World Health Organization standards. ISO administration significantly increased the heart weight and cardiac marker enzymes in serum, xanthine oxidase, sodium, and calcium in the heart, whereas significantly decreased body weight, reduced glutathione, glutathione-S-transferase, superoxide dismutase, and potassium in the heart. Oral pretreatment of TpFE significantly prevented the ISO-induced alterations. This is the first report that revealed the determination of trace elements and mineral nutrients of TpFE by ICP-MS which plays a principal role in the herbal drug discovery for the treatment of cardiovascular diseases.

OMEGA-3 POLYUNSATURATED FATTY ACIDS NORMALIZE THE FUNCTION OF MITOCHONDRIA, ACTIVITY OF ENZYMES OF PROOXIDANT-ANTIOXIDANT SYSTEM AND THE EXPRESSION OF CYTOCHROME Р450 2Е1 AFTER ISOPROTERENOLINDUCED MYOCARDIAL INJURY.

We have studied the influence of dietary ω-3 polyunsaturated fatty acids (ω-3 PUFA) on the functioning of subsarcolemmal and interfibrillar mitochondrial fractions of rat myocardium, changes in expression of cytochrome P450 (CYP2E1) and the activity of enzymes of prooxidant-antioxidant system after isoproterenol-induced myocardial injury. It has been found that in vivo administration of ω-3 PUFA (Epadol 0.1 ml/100 gr of weight for 4 weeks) significantly reduced the swelling of subsarcolemmal and interfibrillar mitochondrial fractions by 65.52% 54.84% respectively, pointing for a decrease of damage of the mitochondrial function evoked by in vivo administration of isoproterenol. In vivo administration of ω-3 PUFAs prevents a decrease in the activity of antioxidant enzymes catalase and superoxide dismutase (2.65 and 7.1- fold, respectively) after isoproterenol-induced myocardial injury. We suggest that the development of oxidative stress after isoproterenol-induced myocardial injury can be caused by a significant increase in the expression of cytochrome P450 2E1 (73.3%), and administration of ω-3 PUFAs prevents such changes.

Triptolide alleviates isoprenaline-induced cardiac remodeling in rats via TGF-ß1/Smad3 and p38 MAPK signaling pathway.

Triptolide (TPL) is a diterpene triepoxide with potent immunosuppressive and anti-inflammatory properties. It is the main effective component of the traditional Chinese herb Tripterygium wilfordii Hook F and has been used in China for centuries to treat immune-related disorders. The present study was conducted to investigate the effects of TPL on cardiac remodeling in rats. Age matched male Wistar rats were used in this study. Cardiac remodeling rat model was established by hypodermic injection of isoprenaline for ten days. The rats were treated with TPL (20 or 100 µg/kg/d) for six consecutive weeks. At the end of the study, the cardiac function, collagen volume fraction, perivascular collagen area and hydroxyproline concentration were studied. Echocardiography, Masson staining, immunohistochemistry, western blot and real-time polymerase chain reaction were performed. The protein and mRNA expression of transforming growth factor-ß1 (TGF-ß1), drosophila mothers against decapentaplegic protein 3 (Smad3) and p38 mitogen activated protein kinase (p38 MAPK) were analyzed. The results indicated that TPL treatment significantly reduced the collagen volume fraction, perivascular collagen area, ventricular weight/body weight ratio and hydroxyproline concentration in myocardial tissue compared with the model group. In addition, it also improved the cardiac function. TPL attenuated cardiac remodeling in rats by down-regulating the p38 MAPK and TGF-ß1/Smad3 signaling pathways. TPL treatment significantly attenuated cardiac fibrosis and improved cardiac function through suppressing the p38 MAPK and TGF-ß1/Smad3 signaling pathway in isoprenaline-induced cardiac remodeling rats. Our findings suggested that TPL might be a novel complementary medicine in the treatment of chronic heart failure.

Dexrazoxane provided moderate protection in a catecholamine model of severe cardiotoxicity.

Positive effects of dexrazoxane (DEX) in anthracycline cardiotoxicity have been mostly assumed to be associated with its iron-chelating properties. However, this explanation has been recently questioned. Iron plays also an important role in the catecholamine cardiotoxicity. Hence in this study, the influence of DEX on a catecholamine model of acute myocardial infarction (100 mg/kg of isoprenaline by subcutaneous injection) was assessed: (i) the effects of an intravenous dose of 20.4 mg/kg were analyzed after 24 h, (ii) the effects were monitored continuously during the first two hours after drug(s) administration to examine the mechanism(s) of cardioprotection. Additional in vitro experiments on iron chelation/reduction and influence on the Fenton chemistry were performed both with isoprenaline/DEX separately and in their combination. DEX partly decreased the mortality, reduced myocardial calcium overload, histological impairment, and peripheral haemodynamic disturbances 24 h after isoprenaline administration. Continuous 2 h experiments showed that DEX did not influence isoprenaline induced atrioventricular blocks and had little effect on the measured haemodynamic parameters. Its protective effects are probably mediated by inhibition of late myocardial impairment and ventricular fibrillation likely due to inhibition of myocardial calcium overload. Complementary in vitro experiments suggested that iron chelation properties of DEX apparently did not play the major role.

Interaction of Semecarpus anacardium L. with propranolol against isoproterenol induced myocardial damage in rats.

With a view to evaluate the cardioprotective effect of ethanolic extract of S. anacardium nut and the possible interaction with propranolol against isoproterenol induced myocardial damage in rats, female Sprague-Dawley rats were pre-treated with propranolol (10 mg/kg for 7 days), low and high doses of S. anacardium (100 and 500 mg/kg for 21 days) and their combination orally and subsequently subjected to isoproterenol administration (150 mg/kg, sc) for two consecutive days. The influence of prophylactic treatment was analysed by quantification of biomarkers and antioxidants, electocardiographic parameters and histopathological observations. The activities of lactate dehydrogenase and creatinine phosphokinase-MB were reduced in serum and raised in heart tissue with concurrent elevation in superoxide dismutase and catalase activities as well as reduction in thiobarbituric acid reactive species levels significantly in all treated groups compared to isoproterenol group. Similarly, electrocardiographic changes were restored to normalcy in all treated groups. To conclude, combination of high dose of S. anacardium with propranolol was found to be most effective in alleviating the abnormal conditions induced by isoproterenol.

Protective effect of Artemisia afra Jacq. on isoproterenol-induced myocardial injury in Wistar rats.

Artemisiaafra Jacq. ex Willd. is a widely used medicinal plant in South Africa for the treatment of various diseases. In this study, the effect of the herb on isoproterenol (ISO)-induced myocardial injury in rats was investigated. Pretreatment with the aqueous leaf extract of the plant at 100 and 200 mg/kg body weight for 30 days prevented the elevation of serum marker enzymes namely lactate dehydrogenase (LDH), aspartate transaminase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) in myocardial injured rats. ISO-induced animals exhibited decreased levels of glutathione reductase (GR), glutathione peroxides (GPx), superoxide dismutase (SOD) and glutathione (GSH) in the heart, which were restored to near normal levels following treatment with the herb. The extract also attenuated lipid peroxidation (LPO) in the heart and improved the imbalance in lipid profile caused by ISO. The effect was more prominent at 200 mg/kg body weight. These findings revealed the cardioprotective effect of A. afra against isoproterenol-induced myocardial injury.

Pomegranate (Punica granatum L.) juice supplementation attenuates isoproterenol-induced cardiac necrosis in rats.

The aim of the present study was to evaluate the efficacy of pre-supplementation with pomegranate (Punica granatum L.) juice (PJ) on heart weight, infarct size, plasma marker enzymes of cardiac damage, lipid peroxidation, endogenous enzymatic and non-enzymatic antioxidants, cardiac ATPases and histopathology of isoproterenol (IP)-induced cardiac necrosis (CN) in rats. Rats treated with IP (85 mg/kg, s.c.) for 2 days at an interval of 24 h caused significant (P < 0.05) infarct in myocardium and increase in heart weight, lipid peroxidation (LPO), activity levels of Ca(+2) ATPase and plasma marker enzymes, while there was significant (P < 0.05) decrease in endogenous enzymatic and non-enzymatic antioxidants and Na(+)-K(+) and Mg(+2)ATPases. Pre-supplementation with PJ for 30 consecutive days and treated with IP on days 29th and 30th showed significantly (P < 0.05) lesser increase in heart weight, infarct size, plasma marker enzymes, lipid peroxidation, Ca(+2) ATPase and a significant protective effect in endogenous enzymatic and non-enzymatic antioxidants, Na(+)-K(+) and Mg(+2) ATPases compared to IP alone treated group. Present study provides first scientific report on protective effect of supplementation of Pomegranate juice against IP-induced CN in rats.

Antioxidant effects of a Rhodobryum roseum extract and its active components in isoproterenol-induced myocardial injury in rats and cardiac myocytes against oxidative stress-triggered damage.

The aim of this study was to investigate (1) whether Rhodobryum roseum, a traditional Chinese medicine used to treat cardiac disease, can protect myocardium damage due to isoproterenol-induced injury, (2) whether the cardioprotective effect of the R. roseum extract is related to its antioxidant activity, and (3) to identify the active components of R. roseum using the oxidant-mediated injury in cardiomyocytes. R. roseum was extracted with 95% EtOH (RE-95), 50% EtOH (RE-50) and water (Re-H2O) and the rats were treated orally for 11 days at doses of 250 mg and 63 mg/kg respectively after cardiac necrosis was induced by administering ISO subcutaneously at a dose of 85 mg/kg body weight. Levels of marker enzymes (LDH, GOT and CK) were assessed in serum whilst the antioxidant parameters, superoxide dismutase (SOD), and malondialdehde (MDA) were assayed in heart homogenate. Significant myocardial necrosis, depletion of endogenous antioxidants and an increase in serum levels of marker enzymes was observed in ISO-treated animals when compared with the normal animals. The RE-50 elicited a significant cardioprotective effect by lowering the levels of serum marker enzymes, lipid peroxidation (MDA). To extend this work, we sought to investigate the antioxidant effects of the components of R. roseum, using the neonatal rat cardiomyocytes model of H2O2-induced oxidant injury. Among the four major components, piperine and methyl piperate significantly reduced the medium level of CK and LDH at a variety of dosages. Moreover, piperine and methyl piperate significantly attenuated 2',7'-dichlorofluorescein (DCF) fluorescence by 63.9% and 52.6%, respectively. The present findings demonstrate that the cardioprotective effects of extracted R. roseum in ISO-induced oxidative damage may be due to an augmentation of the endogenous antioxidants and inhibition of lipid peroxidation of the membranes. Moreover, its components piperine and methyl piperate exert significant protectective effects on cardiac myocytes.

Dietary palm olein oil augments cardiac antioxidant enzymes and protects against isoproterenol-induced myocardial necrosis in rats.

Wistar rats, 150-200 g, of either sex, were fed daily with commercial rat diet supplemented with palm olein oil in two doses (5% v/w (n = 16) and 10% v/w (n = 16) of diet) for 30 days. Control rats (n = 16) were fed with normal diet. On the 29(th) and 30(th) days, 8 rats from each group were administred isoproterenol (85 mg/kg, s.c., 24-h interval). On the 31(st) day, all rats were sacrificed and myocardial tissues were studied for thiobarbituric acid reactive substances (TBARS), antioxidant enzymes and light microscopic changes, along with the ferric-reducing ability of plasma (FRAP). A significant rise in myocardial superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) activity and FRAP level were observed in rats fed with palm olein oil. Isoproterenol caused an increase in myocardial oxidative stress in control rats, as evidenced by an increase in myocardial TBARS level, reduction in FRAP and myocardial SOD, catalase and GPx activity, along with focal necrosis of cardiac muscle fibres on light microscopy. The rise in myocardial TBARS and depletion of SOD and catalase activity following isoproterenol administration were prevented in palm-olein-oil-supplemented diet-fed rats at both doses. Isoproterenol-induced myocardial light-microscopic changes were also prevented in the treated groups. The results suggest that dietary palm olein oil caused augmentation of myocardial antioxidant enzymes and protected against isoproterenol-induced myocardial necrosis and associated oxidative stress.

Chronic oral administration of Ocimum sanctum Linn. augments cardiac endogenous antioxidants and prevents isoproterenol-induced myocardial necrosis in rats.

Wistar rats (200-250 g) of either sex were fed with fresh leaf homogenate of Ocimum sanctum by oral gavage in two different doses, 50 mg kg-1(Os 50) and 100 mg kg-1 (Os 100), daily for 30 days. This was followed by isoproterenol administration (85 mg kg-1 s.c. two doses at 24h intervals) in both control and 0. sanctum-fed rats to induce myocardial necrosis. Hearts were isolated for estimation of endogenous myocardial antioxidants (superoxide dismutase (SOD), catalase, reduced glutathione (GSH) and glutathione peroxidase (GPx) and myocardial lipid peroxidation) and light microscopic study. Increased basal myocardial antioxidant SOD (9.3 +/- 1.2 vs 3.7 +/- 0.7 units mg-1 protein; P<0.05) and catalase activities (34.3 +/- 5.4 vs 17.9 +/- 5.1 units mg-1 protein; P< 0.05) were observed in the Os 50 group only without any evidence of cellular injury in both the groups. In control rats, isoproterenol administration caused significant depletion of myocardial SOD (1.7 +/- 0.2 units mg-1 protein) and GPx (104 +/- 2mU mg-1 protein) activities and increase in GSH (551.7 +/- 30.9, microg g-1 wet weight of tissue) level, with evidence of myocardial necrosis. Isoproterenol-induced changes in myocardial SOD, GPx and GSH were prevented by both the doses of 0. sanctum, however cellular injury was minimal only with 50mg kg-1. The results indicate that long-term feeding of 0. sanctum offered significant protection against isoproterenol-induced myocardial necrosis through a unique property of enhancement of endogenous antioxidants.

In vivo and in vitro characterization of the novel antiarrhythmic agent SSR149744C: electrophysiological, anti-adrenergic, and anti-angiotensin II effects.

SSR149744C (SSR, 2-butyl-3-[4-[3-(dibutylamino)pro-pyl]benzoyl]-1-benzofuran-5-carboxylate isopropyl fumarate), is a new non-iodinated benzofuran derivative. The aim of this study was to evaluate in vivo its electrophysiological, hemodynamic, and anti-adrenergic properties and to determine its mechanism of action using in vitro studies. In chloralose-anesthetized dogs, SSR149744C (1-10 mg/kg i.v.) prolonged the sinus cycle length, A-H interval, Wenckebach cycle length, atrial effective refractory period (ERP), and atrio-ventricular node ERP in a dose-dependent manner without change of ventricular ERP and HV, QRS, or QTc intervals. Arterial blood pressure and ventricular inotropism were slightly decreased. SSR149744C, which has no or low affinity for alpha 1 and beta 1 adrenergic and angiotensin II AT1 receptors, reduced isoproterenol-induced tachycardia and phenylephrine- or angiotensin II-induced hypertension in anaesthetized dogs. In guinea pig papillary muscle, SSR149744C did not modify the resting potential, action potential amplitude and duration, but reduced the dV/dt max of the depolarization phase in a frequency-dependent manner. In isolated guinea pig cardiomyocytes and transfected CHO cells, SSR149744C (0.01-30 microM) inhibited several potassium currents: IKr (IC50 approximately 10 microM), IKs (IC50 approximately 30 microM), IK(ACh) (IC50 = 0.09 microM), and IKv1.5 (IC50 = 2.7 microM), the L-type calcium current: ICa(L) (IC50 approximately 5 microM) and also the amplitude of [Ca2+]i transient and cell shortening. Therefore, SSR149744C appears to have a multifactorial mechanism of action, which combines the blockade of several ion channels with the inhibition of responses of alpha 1 and beta 1 adrenergic as well as AT1 receptor stimulation. Like amiodarone, SSR149744C possesses the pharmacological effects of class I, II, III, and IV antiarrhythmic agents, which may confer upon this new drug a strong antiarrhythmic potential without ventricular proarrhythmia and iodine-related amiodarone-like side-effects.

[Effect of zhimu and huangqi on cardiac hypertrophy and response to stimulation in mice].

OBJECTIVE: To observe the effect of Zhimu and Huangqi on increasing heart rate and cardiac hypertrophy, and its bradycardia effect, to evaluate the exercise capacity and response to stimulation and to discuss the use of Zhimu in treating heart failure. METHOD: 1. Rats were treated with isoproterenol 1.25 micrograms.kg-1 i.p., and then the increasing of heart rate and the bradycardia effect were measured after administrated with Zhimu or Huangqi for 3 days. 2. Mice cardiac hypertrophy model was established by s.c. ISO 1 mg.kg-1, 2 times per day for 14 days and heart-weight-index was measured after Zhimu and Huangqi was given orally alone or jointly for 14 days. 3. Abdominal aorta banding operation was done in mice and 3 weeks after operation, they were administrated for 2 weeks, and then run-time(exercise capacity), quiet heart rate, ISO response heart rate after i.p. isoproterenol and heart-weight-index were measured. 4. Cardiac hypertrophy model (inject ISO 14 days) mice were administrated for 12 days, and the mortality and dying time of mice in cold (-20 degrees C) and heat(45 degrees C) stimulative condition were observed. RESULT: Zhimu could cut down the increasing of heart rate induced by ISO, decrease significantly heart-weight-index in cardiac hypertrophy mice, reduce the quiet heart rate and prolong the run time in abdominal banding model. Zhimu combined with Huangqi could also improve the ISO response in abdominal banding model mice, reduce the mortality and delay dying time of mice in stimulative condition. CONCLUSION: Zhimu combined with Huangqi can slow down heart rate, enhance the reserve force of the heart, and improve the response capacity of cardiac hypertrophy mice in stimulative condition.

Levobetaxolol (Betaxon) and other beta-adrenergic antagonists: preclinical pharmacology, IOP-lowering activity and sites of action in human eyes.

The pharmacological characteristics of levobetaxolol, a single active isomer of betaxolol, were determined and compared with activities of other beta-adrenoceptor antagonists. Levobetaxolol (43-fold beta1-selective) exhibited a higher affinity at cloned human beta1 (Ki = 0.76 nM) than at beta2 (Ki = 32.6 nM) receptors, while dextrobetaxolol was much weaker at both receptors. Levobetaxolol potently antagonized functional activities at cloned human beta1 and beta2 receptors, and also at guinea pig atrial beta1, tracheal beta2 and rat colonic beta3 receptors (IC50s = 33.2 nM, 2970 nM and 709 nM, respectively). Thus, levobetaxolol was 89-times beta1-selective (vs beta2). Levobetaxolol (Ki = 16.4 nM) was more potent than dextrobetaxolol (Ki = 2.97 microM) at inhibiting isoproterenol-induced cAMP production in human non-pigmented ciliary epithelial cells. Levobunolol and (l)-timolol had high affinities at beta1 and beta2 receptors but were considerably less beta1-selective than levobetaxolol. Levo-, dextro- and racemic-betaxolol exhibited little or no affinity, except at sigma sites and Ca2+-channels (IC50s > 1 microM), at 89 other receptor/ligand binding sites. Levobetaxolol exhibited a micromolar affinity for L-type Ca2+-channels. In conscious ocular hypertensive cynomolgus monkeys, levobetaxolol was more potent than dextrobetaxolol, reducing intraocular pressure by 25.9+/-3.2% at a dose of 150 microg/eye (n = 15-30). Quantitative [3H]-levobetaxolol autoradiography revealed high levels of binding to human ciliary processes, iris, choroid/retina, and ciliary muscles. In conclusion, levobetaxolol is a potent, high affinity and beta1-selective IOP-lowering beta-adrenoceptor antagonist.

[The protective effects of yi-xin-kang capsule on the structure and function of rat myocardial mitochondria].

OBJECT: To observe the injury induced by Isoproterenol (ISO) on the structure and function of rat myocardial mitochondria and the protective effects of Yi-Xin-Kang Capsule (H303). METHOD: After injection of ISO, rat myocardial mitochondria were isolated. The activities of phospholipidase A2(PLA2) and Ca(2+)-ATPase, the content of phospholipids (PL) and high-energy phosphates, membrane lipid fluidity (LFU) and respiration function were determined respectively. RESULT: ISO induced severe injury to myocardial mitochondria. The activity of PLA2 was significantly activated. The intensity of LFU, the activity of Ca(2+)-ATPase, respiration function of mitochondria and the contents of PL and high-energy phosphates of myocardium tissue were significantly decreased. Oral administration of H303 significantly decreased the activity of PLA2. The contents of PL and LFU, the activity of Ca(2+)-ATPase were significantly increased. The respiration function of mitochondria was protected by accelerating III state respiration rate, improving ADP/O ratio and recovering the depressed respiration control rate. CONCLUSION: H303 possessed protective effect on structural and functional injury of mitochondria induced by ISO.

Beta adrenergic receptors facilitate norepinephrine release from rat hypothalamic and hippocampal slices.

Basal and electrical stimulation-induced release of tritiated norepinephrine (3H-NE) was determined in superfused slices of the rat hypothalamus and hippocampus. Isoproterenol (0.1-10 nM), a nonselective beta-adrenergic agonist, enhanced stimulation-evoked release of 3H-NE from hypothalamic and hippocampal slices in a concentration-dependent manner without consistently altering basal release. Isoproterenol (1 nM) increased ratios of S2/S1 to 143 +/- 4% (hypothalamus) and 152 +/- 15% (hippocampus) of control values. The facilitatory effects of isoproterenol were antagonized by propranolol (50 nM), a nonselective beta-adrenergic antagonist. The beta 2-selective adrenergic agonist clenbuterol (10-100 microM) enhanced basal release of 3H-NE in a concentration-dependent fashion. These results provide evidence for a beta-adrenergic receptor mediated regulation of NE release from hypothalamic and hippocampal slices. Whether the positive feedback mechanism contributes to any of the NE-mediated physiological functions associated with the hypothalamus and hippocampus requires further study. However, the effect of clenbuterol indicates that some of its behavioral actions in animals may be attributed to this NE release-enhancing effect observed in the present study.

Refractory hypothalamic adenylate cyclase in anorectic tumor-bearing rats: implications for NPY-induced feeding.

Although isoproterenol stimulated adenylate cyclase activity in hypothalamic membranes taken from freely-feeding, food-restricted or nonanorectic tumor-bearing rats, the response was greatly reduced in anorectic tumor-bearing rats. The addition of NPY to the membrane preparation inhibited adenylate cyclase activity in hypothalamus taken from freely-feeding and food-restricted rats, but NPY-inhibitory activity was significantly reduced in both groups of tumor-bearing rats. These results suggest that cyclic AMP formation is refractory in anorectic tumor-bearing rats, and that NPY-induced inhibition of hypothalamic adenylate cyclase is reduced in tumor-bearing rats prior to the onset of significant anorexia. Therefore, NPY-induced feeding may be reduced in tumor-bearing organisms due to a dysfunction in the cyclic AMP second messenger system.

Effects of osthole on isolated guinea pig heart atria.

AIM: To study the effects of osthole (Ost) on the isolated guinea pig atria and the relationship between Ost effect and Ca2+. METHODS: Contractions of left atria were induced by electric stimulations. The contractile amplitude of left atria pre- and post-treated with Ost was measured according to the cumulative concentration method, the drug being added at 15 min intervals, the pA2 or pD2' were calculated. It were measured that the effects of Ost to the positive staircase and to the post-rest potential enhancement. The contractile responses were recorded via an auto-equiolibration recording instrument. RESULTS: Ost 10-300 mumol.L-1 and Ver 0.1-30 mumol.L-1 decreased the contractile force and inhibited the isoprenaline-induced restoration of contractile response in the left atria rendered inexcitable by KCl 25 mmol.L-1. Ost and Ver antagonized the CaCl2- and isoprenaline-induced positive inotropic response noncompetively, the pD2' values to Ost were 4.41 +/- 0.13 and 4.90 +/- 0.15, to Ver were 6.53 +/- 0.22 and 6.91 +/- 0.17, respectively. Both of them inhibited the contraction of the left atrium and reversed the frequency-contraction response from positive to negative staircase in the higher dosage (500 and 1 mumol.L-1), but they showed only slight inhibitory effect on post-rest potentiation. CONCLUSION: Ost was similar to, but much less potent than Ver in inhibiting the isolated guinea pig atria.

Prevention and termination of beta-adrenergic agonist-induced arrhythmias by free polyunsaturated fatty acids in neonatal rat cardiac myocytes.

Polyunsaturated omega-3 fatty acids, which have been shown to prevent ischemia-induced ventricular fibrillation in prepared dogs, were tested in cultured neonatal rat cardiac myocytes for their ability to prevent the tachyarrhythmias induced by isoproterenol, a beta-adrenergic agonist. We found that polyunsaturated fatty acids (5-10 microM), especially the fish oil omega-3 fatty acids, but not monouunsaturated and saturated fatty acids were able to effectively prevent and terminate the arrhythmias induced by isoproterenol (as well as by cAMP and cholera toxin) without affecting the cell contractility, and that their action was independent of their metabolites and incorporation into membrane phospholipid. These protective effects of the free fatty acids may contribute, at least in part, to their reported preventive effects on ischemia-induced ventricular fibrillation and sudden cardiac death.