X indening oral liquid improves cardiac function of rats with chronic cardiac failure via TGF-ß1/Smad3 and p38 MAPK pathway.

OBJECTIVE: Xindening oral liquid (Xin) is a widely used traditional Chinese medicine for the treatment of chronic heart failure (CHF). However, the exact mechanisms related to its therapeutic effects against CHF remain unclear. In the present study, we investigate the effects of Xin on cardiac function in CHF rats and the possible mechanisms involved. METHODS: Transverse aortic constriction (TAC) was conducted to induce a CHF rat model in this study. Sixty male Wistar rats were randomly assigned to six groups 28 days after TAC: sham; CHF model; Xin at concentrations of 5 ml/kg, 10 mL/kg, and 20 mL/kg; and QiLi 0.6 g/kg. After four weeks, the rats were treated with Xin (5, 10, or 20 mL/kg/d) for six weeks consecutively. At the end of the study, the cardiac function, heart weight index (HWI) and left ventricular mass index (LVMI), serum level of LDH, B-type natriuretic peptide (BNP), cTnI and CK-MB, and collagen volume fraction were studied. The expression of transforming growth factor-ß1 (TGF-ß1), drosophila mothers against decapentaplegic protein 3 (Smad3), and p38 mitogen activated protein kinase (p38 MAPK) were detected. RESULTS: The results showed that Xin treatment significantly improved cardiac function but decreased the serum level of LDH, BNP, cTnI, and CKMB of CHF rats. In addition, it reduced the HWI, LVMI, and collagen volume fraction compared with the model group. Xin treatment significantly improved cardiac function and attenuated cardiac fibrosis by suppressing the p38 MAPK and TGF-ß1/Smad3 signaling pathway in CHF rats. CONCLUSION: These results suggested that Xin might be a promising complementary treatment for CHF. More detailed experimental studies will be carried out in our subsequent research.

Effect of a calcium-sensitizing agent, levosimendan, on the postcardioplegic inotropic response of the myocardium.

Myocardial contractile function after coronary artery bypass graft surgery is often depressed and may require inotropic support, particularly in patients on treatment with beta-adrenergic and Ca2+ blockers. In view of the increase in cytosolic Ca2+ during early reperfusion, use of Ca2+ sensitizing agents may be preferable to adrenergic agonists for enhancement of contractile function after cardioplegic arrest. The aim of this study was to assess the efficacy of the Ca2+ sensitizer, levosimendan, as an inotrope on the mechanical recovery of hearts after normothermic and hypothermic cardioplegic arrest in the absence and presence of Ca2+ and beta-blockers. Isolated perfused working guinea pig hearts were perfused in the absence or presence of propranolol (10(-6) M) and/or nifedipine (10(-8) M), subjected to 45 minutes of normothermic or 180 minutes of hypothermic cardioplegic arrest, reperfused, and exposed to increasing concentrations of levosimendan (10(-9) to 10(-6) M). Levosimendan (10(-7) to 10(-6) M) has positive inotropic, chronotropic, and vasodilatory effects on normoxic perfused control hearts, as well as during reperfusion after 45 minutes of normothermic cardioplegic arrest. Similar effects were elicited in the presence of the blockers. Levosimendan had no stimulatory effect during reperfusion of hearts subjected to prior hypothermic arrest. Except for the increase in heart rate, the effects of levosimendan on functional performance during reperfusion were comparable with those of adrenaline. Levosimendan elicits a positive inotropic and chronotropic response during reperfusion of hearts after normothermic cardioplegic arrest, both in the absence and presence of Ca2+ and beta-adrenergic blockers.

Constitutively active mutants of the beta1-adrenergic receptor.

We provide the first evidence that point mutations can constitutively activate the beta(1)-adrenergic receptor (AR). Leucine 322 of the beta(1)-AR in the C-terminal portion of its third intracellular loop was replaced with seven amino acids (I, T, E, F, C, A and K) differing in their physico-chemical properties. The beta(1)-AR mutants expressed in HEK-293 cells displayed various levels of constitutive activity which could be partially inhibited by some beta-blockers. The results of this study might have interesting implications for future studies aiming at elucidating the activation process of the beta(1)-AR as well as the mechanism of action of beta-blockers.

Nonspecific membrane effects of CH-103: hydrophobicity, surface activity and membrane fluidity studies in comparison with propranolol and practolol.

The partition coefficient, surface activity and membrane fluidizing/disordering effects of CH-103, a beta-adrenergic receptor antagonist, were compared to those of propranolol and practolol as reference compounds. Changes in membrane fluidity were followed by measuring the steady-state fluorescence anisotropy of bull sperm cells with 1-[4-(trimethylammonium)-phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) as a fluorescence probe. The octanol/buffer (pH 7.0) partition coefficients for CH-103, propranolol and practolol were 32.9, 5.08 and 0.013, respectively; the surface activity of the compounds decreased in the same order. CH-103 and propranolol significantly increased the fluidity of the membrane in a concentration-dependent manner, whereas practolol reduced fluidity. These physicochemical parameters correlated with the effects of these drugs on rat sarcolemmal Ca2+, Mg(2+)-ATPase, a manifestation of their nonspecific membrane activity. Our results suggest that the physicochemical properties of CH-103, similarly to those of propranolol, are the main determinants of its nonspecific membrane activity.

Potentiation by higenamine of the aconitine-induced positive chronotropic effect in isolated right atria of mice: the effects of cholera toxin, forskolin and pertussis toxin.

Aconitine and higenamine are the major cardioactive compounds obtained from processed aconite. The chronotropic interaction between these two compounds was investigated in isolated right atria of mice. Both aconitine and higenamine potentiated the action of the other. Practolol (1 nM), a selective beta 1-adrenergic antagonist, but not butoxamine (1 microM), a beta 2-adrenergic antagonist, blocked the potentiation by higenamine (5 nM) of the aconitine-induced positive chronotropic effect and, at high concentrations (30 and 300 nM) also shifted the aconitine concentration-response curves to the right. The potentiating interaction between aconitine and higenamine was reversed by pretreating with cholera toxin (CTX) and forskolin. In CTX (100 nM, 1 h)- and forskolin (30 and 100 nM)-treated atria, higenamine significantly depressed the aconitine-induced response, which was abolished by pertussis toxin (PTX, 150 micrograms/kg, i.p., 3 d). Neither CTX (50 and 100 nM) nor forskolin (15-100 nM) significantly affected the aconitine-induced positive chronotropic effect, while PTX (150 micrograms/kg) depressed it. These results suggest that the potentiating interaction between aconitine and higenamine involves "cross-talk" between the beta 1-adrenergic signalling pathway and Gi-protein.

Effect of levamisole hydrochloride on the guinea-pig atrium.

The effects of levamisole on the guinea-pig atrial preparation were determined. At 3 micrograms/ml, levamisole and lignocaine prevented electrically induced arrhythmia in 3 and 5 out of 5 preparations respectively. It was concluded that levamisole at the therapeutic anthelmintic dose would not abolish clinical atrial arrhythmia. Levamisole even at 3 micrograms/ml had definite salutary effect on the hypodynamic state induced by continuous electrical stimulation. The dose-related positive inotropic effect of levamisole 5-200 micrograms/ml was not antagonised by practolol but was absent in atria from reserpinized animals. Therefore, cAMP may not be involved in the positive inotropic effect. Levamisole antagonised verapamil-induced negative inotropic effect and no positive inotropic effect was observed when the Ca2+ content of the Ringer-Locke solution was below normal. These suggested that Ca2+ must be involved in the inotropic effect. The negative chronotropic effect due to levamisole was not antagonised by hexamethonium but was antagonised by atropine, thus indicating that stimulation of M1 or M2 receptors in the atria may be responsible.

On the relationship between the inhibition of thrombin stimulated aggregation and thromboxane formation in isolated platelets treated with beta-adrenoceptor blocking drugs.

Thromboxane B2 (TXB2) formation in isolated, thrombin-stimulated rat platelets was time dependent and appeared after 5 s of incubation. Beta-adrenoceptor blocking (BAB) drugs inhibited thrombin-stimulated TXB2 formation in the following rank order of potency: metipranolol approximately alprenolol approximately propranolol > oxprenolol > practolol. Atenolol was ineffective in inhibiting TXB2 production in stimulated platelets. The inhibition of thrombin-stimulated TXB2 formation by BAB drugs correlated with their inhibitory effect on thrombin-stimulated platelet aggregation, arachidonic acid liberation from membrane phospholipids and with their membrane fluidization. The higher was the liposolubility of the beta-adrenoceptor blocking drugs investigated, the higher was their inhibition of stimulated TXB2 formation. Hydrophilic, selective atenolol and practolol revealed slight or no inhibitory effect on stimulated thromboxane production.

Prostaglandin E2 synthesis elicited by adrenergic stimuli in guinea pig trachea is mediated primarily via activation of beta 2 adrenergic receptors.

Prostaglandin (PG) E2 synthesis elicited by adrenergic agonists in the guinea pig trachea has been shown to be mediated via activation of beta-adrenergic receptors. The purpose of this study was to examine arachidonic acid (AA) metabolism and to characterize the subtype of beta receptor involved in PG synthesis. [14C]AA was incubated with guinea pig tracheal rings, and the radiolabelled products were extracted from the medium. Thin layer chromatographic analysis and radioimmunoassay of the extract showed that [14C]AA was incorporated into guinea pig tracheal rings and metabolized mainly into radiolabeled and immunoreactive PGE2 (iPGE2) and smaller amounts into PGF2 alpha. Trace amounts of PGD2, TxB2 and 6-keto-PGF1 alpha but not LTB4 or LTC4 were detected by enzyme immunoassay. Incubation of guinea pig tracheal rings for 10 min with isoproterenol or salbutamol resulted in a significant increase in PGE2 synthesis (optimum concentration 0.1 microM for both compounds). In contrast, dobutamine, BRL 37344, BRL 28410, norepinephrine, phenylephrine, and xylazine (up to 1 microM) did not significantly increase PGE2 production. Isoproterenol-induced iPGE2 production was inhibited by the selective beta 2 receptor antagonist butoxamine (0.1-1.0 microM) and somewhat reduced by the beta 1 receptor antagonist practolol (1 microM). The increase in PGE2 synthesis was diminished with increasing concentrations of isoproterenol (0.5-5.0 microM) or salbutamol (0.5-1.0 microM); but it was reversed by pretreatment of tracheal rings with the protein synthesis inhibitors cycloheximide (0.9 microM) and actinomycin D (2 microM) but not by phenylisopropyl adenosine (0.1-1.0 microM), an inhibitor of adenylyl cyclase. These data suggest that isoproterenol-induced iPGE2 synthesis is primarily via activation of a beta 2 adrenergic receptor. Failure to enhance iPGE2 synthesis by a high concentration of isoproterenol is likely to be due to an induction of new inhibitory protein synthesis.

Further evidence showing that the inhibitory action of serotonin on rat masculine sexual behavior is mediated after the stimulation of 5-HT1B receptors.

To explore whether the inhibitory actions of endogenous serotonin on rat male sexual behavior were mediated via the stimulation of the 5-hydroxytryptamine1A (5-HT1A) or 5-HT1B receptor subtypes, two series of studies were undertaken. In the first series, an attempt to block the inhibitory actions of threshold doses of the serotonin precursor 5-hydroxytryptophan (5-HTP, 50 mg/kg) by administering the beta-5-HT antagonist alprenolol (5.0 mg/kg) and the selective beta-blocker practolol (0.5 mg/kg) was made. Both antagonists effectively prevented, at least partially, the inhibitory actions of 5-HTP. In the second series, a possible synergistic effect of a subthreshold dose of 5-HTP (12.5 mg/kg) with low doses of the selective 5-HT1B agonist 1-(m-trifluoro-methylphenyl)piperazine (TFMPP,0.125 mg/kg) or the selective 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT, 0.0625 mg/kg) was investigated. A clear synergistic inhibitory effect of 5-HTP with TFMPP was observed. All data are interpreted based upon the hypothesis suggesting a physiological inhibitory role of the 5-HT1B receptor subtype on male rat sexual behavior.

Preoptic norepinephrine-induced hypothermia is mediated by alpha 2-adrenoceptors.

We have shown previously that norepinephrine (NE) microdialyzed into the preoptic area of conscious guinea pigs evokes a fall in core temperature (Tco) that is mediated by a reduction in metabolic rate. To identify the adrenoceptor subtype(s) involved in this effect, we microdialyzed intrapreoptically various adrenergic agonists or antagonists singly or in combinations. Tco and ear skin temperatures of the animals were monitored throughout the experiments. alpha 1-, beta-, beta 1-, and beta 2-agonists and antagonists did not induce significant Tco changes. Although the alpha 2-antagonists yohimbine (Yoh) and rauwolscine (Rau) did not have thermal effects per se, the alpha 2-agonist clonidine evoked dose-dependent Tco falls that were abolished by codialyzed Yoh and Rau. The microdialysis of NE evoked, as before, a 0.7 +/- 0.2 degrees C Tco fall; it was abolished by the codialyzed alpha-antagonist phentolamine, Yoh, and Rau but not by the beta-antagonist propranolol. No adrenoceptor agonist induced changes in ear skin temperature. These results indicate that the hypothermizing effect of intrapreoptically microdialyzed NE is achieved by a reduction in metabolic heat production, mediated by alpha 2-adrenoceptors.

[The effect of practolol and atenolol on the lysosomal enzyme activity of the ventricular myocardium of rats]. / Vliianie praktolola i atenolola na aktivnost' lizosomal'nykh fermentov miokarda zheludochkov krys.

The influence of cardioselective beta-blockers, practolol and atenolol, on acid phosphatase, acid deoxyribonuclease, cathepsin D, beta-glucosidase and beta-galactosidase activities was studied in homogenates of intact rat ventricular myocardium. In the presence of drugs (1 x 10(-9)-1 x 10(-5) M) the activities of acid phosphatase, cathepsin D, beta-glucosidase and beta-galactosidase tended to diminish but the activity of acid deoxyribonuclease tended to increase. Some differences in the influence of drugs on the enzyme activities were removed by prolongation of preincubation of homogenates with drugs. It is supposed that the mechanism of influence of beta-blockers on lysosomes of the intact rat ventricular myocardium in conditions of this study includes the specific drug binding to beta-adrenergic receptors situated on lysosomes.

Role of central beta-adrenoceptors on stress-induced prolactin release in rats.

Adult Wistar male rats underwent immobilization stress (IS) during forty minutes. PRL secretion presented a remarkable increase after 5 minutes, and it was higher than pre-stress values during the entire duration of the experiment. The blockade of beta-1 adrenoceptors by icv injections of practolol did not modify IS-induced PRL release. IPS 339, a selective antagonist of beta-2 adrenoceptors, also injected icv, reduced PRL secretion during stress in a dose dependent fashion. The blockade of PRL secretion due to IPS 339 was reverted by a previous icv administration of salbutamol, a classical beta-2 agonist. The data presented here suggest that central beta-2 adrenoceptors activation is an important step in the control of stress-induced PRL secretion.

A comparison of the inotropic effects of dopamine and epinine in human isolated cardiac preparations.

The positive inotropic effects of epinine and dopamine have been studied in isolated preparations obtained from human heart in the absence and in the presence of the selective beta adrenoceptors antagonists practolol and ICI 118,551. ED50 values of the two agonists were similar (about 3 x 10(-5) M). The inotropic efficacy of epinine was significantly higher than that of dopamine in adult ventricular and papillary muscles, it was similar to that of dopamine in juvenile myocardial preparations and in adult atria and pectinate muscles. The dopamine-evoked response was significantly more sensitive to practolol than epinine-evoked response, but it was less sensitive to ICI 118,551. pA2 values of practolol and ICI 118,551 were considerably different with epinine but not with dopamine as agonist. The results indicate that, compared to dopamine in isolated human heart preparations, epinine was more potent at beta-2 relative to beta-1 adrenoceptors.

Study of the contraction induced by norepinephrine and clonidine in the isolated guinea-pig ileum.

1. Norepinephrine (NE) and clonidine produce a phasic, dose-dependent contraction of the isolated guinea-pig terminal ileum. 2. The effect of NE was blocked by prazosin which produced a parallel rightward shift of the concentration-effect curve to NE, with a significant depression of maximum effects. 3. Yohimbine and indomethacin noncompetitively blocked, whereas practolol potentiated, the contractile effect of NE. 4. The contractile effect of clonidine was not antagonized by indomethacin or atropine. 5. These results suggest that the isolated guinea-pig terminal ileum has excitatory receptors sensitive to clonidine stimulation and excitatory alpha receptors sensitive to blockade by prazosin, and that the activation of the latter may be related to the activation of endogenous prostaglandin synthesis.

Beta adrenoceptors mediate the catecholamine-induced stimulation of oxytocin secretion from cultured bovine granulosa cells.

Bovine granulosa cells were treated in culture with alpha- and beta-adrenoceptor ligands to determine the receptor subtype mediating their response to catecholamines. The secretion of oxytocin by granulosa cells in serum-free medium was measured on the fourth day of culture (during the period of acquisition of a luteal phenotype). Cultures were performed in the presence of 0.5 mM ascorbic acid, which increased hormone output and potentiated the response to catecholamines. The effects of adrenaline and noradrenaline on oxytocin secretion were concentration-dependent; maximum stimulation was over 700% with adrenalin (EC50 92 nM) and 500% with noradrenaline (EC50 87 nM). The response to noradrenaline (10(-6) M) and adrenaline (10(-6) M) could be blocked by propranolol but not by phentolamine, suggesting that beta- rather than alpha-adrenoceptors were involved. Blockade by metoprolol and practolol (beta 1-adrenoceptor antagonists) was poor and dobutamine (beta 1-agonist) was weakly stimulatory. A concentration-dependent stimulatory response (EC50 200 nM) was obtained with salbutamol (beta 2-adrenoceptor agonist) and stimulation by adrenaline or salbutamol could be blocked by a selective beta 2-adrenoceptor antagonist (ICI 118,551). It is concluded that, during luteinization, the long-term response of bovine granulosa cells to stimulation induced by catecholamines is mediated through beta- rather than alpha-adrenoceptors. Although the beta 2-subtype is probably involved, the similar potencies of adrenaline and noradrenaline are uncharacteristic of beta 2-adrenoceptors and may be peculiar to the long-term response shown by these cells.

Pharmacological responses to dopamine in isolated guinea-pig cardiovascular tissues: mechanisms of action.

The mechanisms responsible for the positive inotropic, positive chronotropic and vasoconstrictor responses to dopamine in isolated guinea-pig cardiovascular tissues have been investigated in the present study. Since dopamine is the immediate precursor of noradrenaline, the role of noradrenaline in the pharmacological responses after addition of dopamine has been assessed. In isolated, contracting right ventricular papillary muscles, dopamine-induced positive inotropy (-log EC50, 4.77 +/- 0.06) was unaltered by incubation with dopamine antagonists (SCH 23390, domperidone), alpha-adrenoceptor antagonists (prazosin, yohimbine), or an inhibitor of uptake1 (cocaine). Practolol (selective beta 1-adrenoceptor antagonist) and ICI 118,551 (selective beta 2-adrenoceptor antagonist) were noncompetitive antagonists to dopamine. Block of vesicular uptake by reserpine antagonized the positive inotropic responses to dopamine (-log EC50, 4.03 +/- 0.05) but not to noradrenaline; these responses were antagonized by both practolol and ICI 118,551. Chemical sympathectomy by 6-hydroxydopamine antagonized the responses to dopamine (-log EC50, 3.76 +/- 0.11) but potentiated the responses to noradrenaline (-log EC50, 7.35 +/- 0.07). Inhibition of monoamine oxidase with pargyline potentiated the responses to dopamine (-log EC50, 6.05 +/- 0.04) and noradrenaline; the potentiation of dopamine responses was unaffected by chemical sympathectomy. Inhibition of dopamine beta-hydroxylase with sodium diethyldithiocarbamate antagonized the inotropic responses to dopamine (-log EC50, 4.36 +/- 0.05) but not to noradrenaline. Similar results were obtained in guinea-pig left atria (positive inotropy) and right atria (positive chronotropy), except that chemical sympathectomy failed to affect the chronotropic responses. In thoracic aortic rings, dopamine contracted vascular smooth muscle by direct partial agonism of alpha 1-adrenoceptors, without involvement of dopamine beta-hydroxylase. Thus, there is antagonism of the cardiac, but not the vascular responses to dopamine by inhibition of dopamine beta-hydroxylase. This shows that the conversion of dopamine to noradrenaline is important in the inotropic and chronotropic responses, but not the vascular responses to dopamine.

Pharmacological evaluation of new alkylesters of 4-[(2-hydroxy-3-alkylamino)propoxy]phenylcarbamic acids with beta-adrenolytic properties.

The basic relationship between the chemical structure and pharmacological activities of new alkylesters of 4-[(2-hydroxy-3-alkylamino)propoxy]phenylcarbamic acids were evaluated. The efficiency of compounds was compared with those of metipranolol and practolol, respectively. The majority of 4-substituted derivatives of aryloxypropanolamines have shown antiisoprenaline (beta-adrenolytic) and local anesthetic (membrane stabilizing) activities. The values of LD50 and/or partition coefficients have not differed significantly when compared with those of standard metipranolol.

Beta-receptor subtypes in the canine coronary circulation.

The principal difficulty in determining the subtype of coronary vascular beta-receptors in vivo is to avoid the local metabolic coronary vasodilation that occurs secondary to activation of myocardial beta-receptors. Therefore, a nonbeating cardiac preparation without chronotropic or inotropic effects is needed. In this study, the coronary circulation was perfused at constant pressure in closed-chest chloralose-anesthetized dogs. The increase in coronary blood flow due to intracoronary injections of the combined beta 1- and beta 2-agonist isoproterenol was determined during prolonged asystoles after the cessation of cardiac pacing in atrioventricular heart-blocked animals. Both beta 1-selective (practolol and L 650,744) and beta 2-selective (ICI 118,551) antagonists blocked isoproterenol-induced coronary vasodilation. In contrast, isoproterenol vasodilation in the femoral circulation was blocked by beta 2- but not by beta 1-selective antagonists. In conclusion, both beta 1- and beta 2-receptors in coronary resistance vessels are stimulated by isoproterenol to produce vasodilation during prolonged asystoles, when cardiac chronotropic and inotropic effects are absent.

Major histocompatibility complex modulation of beta-adrenoceptor function.

Reciprocal interaction between beta-adrenoceptor specific ligand occupancy and alloantibody binding to specific antigens of cardiac and smooth muscle tissues was observed. Interference of alloimmune antibody fixation to both cardiac and oviductal tract preparations by beta 1 or beta 2 selective blockers, respectively, was obtained by means of indirect immunofluorescence assays. Reciprocally, alloimmune IgG and monoclonal antibodies directed to class I H-2 antigens, behaving as beta-adrenoceptor agonists, modified the contractility of both tissues, increasing intracellular levels of cyclic AMP (cAMP). Additionally, alloantibodies were also capable of inhibiting specific beta-adrenoceptor radioligand binding to purified cardiac and smooth muscle membranes. These data suggested a modulation of beta-adrenoceptor function by antibodies directed against H-2 class I histocompatibility molecules, probably through molecular interactions between both structures.