Effect of Humic Acids from Lowland Peat on Endurance of Rats in Forced Swim Test in Relation to Serum Lactate and Corticosterone.

The study substantiated the possibility of using peat humic acids for improving endurance during extreme physical exertion. The mature outbred Wistar rats weighing 200-250 g (n=40) were subjected to forced swim test until complete exhaustion. The humic acids (1%) were administered intragastrically (0.5 ml/100 g body weight) 30 min prior to the test. Chronic administration of peat humic acids for 5 days increased physical capacity and endurance of rats in exhaustive forced swim test without the changes in serum lactate and corticosterone.

The Role of NO Synthase in the Cardioprotective Effect of Substances of Humic Origin on the Model of Ischemia and Reperfusion of Isolated Rat Heart.

The cardioprotective and inotropic effects of standardized active natural substance based on high-molecular-weight compounds of humic origin were studied on the model of global ischemia (40 min) and reperfusion of isolated perfused rat heart. Preventive administration of the test substance (0.1 mg/ml) before ischemia/reperfusion modeling reduced reperfusion contracture and necrotic death of cardiomyocytes and promoted recovery of myocardial contractility. Blockade of NO synthase with L-NAME (100 µM) abolished the above effects of the test substance. It was hypothesized that NO synthase plays an important role in the development of the cardioprotective and inotropic effects of the test natural substance.

Involvement of Autonomic Nervous System in Antiarrhythmic Effect of Intermittent Hypobaric Hypoxia.

We studied the involvement of the autonomic nervous system in the antiarrhythmic effect of intermittent hypobaric hypoxia modeled by daily placing the rats into an altitude chamber at 405 mm Hg (5000 m above sea level). The antiarrhythmic effect of hypoxia was observed on the model of acute coronary occlusion/reperfusion in vivo, but not during simulation of total ischemia/reperfusion of the isolated myocardium. Intravenous injection of ganglionic blocker hexamethonium (30 mg/kg) 15 min prior to in vivo coronary occlusion modeling abolished the antiarrhythmic effect of intermittent hypobaric hypoxia, which suggests that this effect is mediated via activation of the autonomic nervous system.

Cardiovascular Effects of High-Molecular-Weight Compounds of Humic Nature.

The active ingredient extracted from the peat humic substances was characterized by physicochemical parameters evaluated by UV- and IR-spectroscopy, titration, and elemental (C, H, N) analysis. The cardiovascular effects of this ingredient were examined on isolated Langendorff-perfused rat heart. It was found that the active substance in a concentration range of 0.01-0.1 mg/ml produced a vasodilating effect; in addition, it decreased the end-diastolic and left-ventricular developed pressures.

Effects of µ-Opioid Receptor Agonist DAMGO on Heart Contractility and Necrotic Injury to Cardiomyocytes during Ischemia and Reperfusion of Isolated Rat Heart.

We studied the effects of µ-opioid receptor activation in vivo and in vitro on the tolerance of isolated perfused rat heart to global ischemia (45 min) and reperfusion (30 min). Stimulation of µ-receptors in vivo by intraperitoneal administration of µ-opioid receptor agonist DAMGO (0.1 mg/kg) reduced reperfusion release of creatinine phosphokinase and promoted aggravation of postischemic systolic and diastolic dysfunction of the isolated heart. Activation of µ-opioid receptors in vitro by addition of selective agonist DAMGO in a concentration of 170 nM to perfusion solution had no effect on necrotic death of cardiomyocytes and aggravated reperfusion stunning of the heart.

Cardioprotective Activity of Ganoderma lucidum Extract during Total Ischemia and Reperfusion of Isolated Heart.

The cardioprotective effects of Ganoderma lucidum extract were examined in experiments with global ischemia (45 min) and reperfusion (30 min) of isolated and perfused rat heart. The course of preventive administration of the extract in a dose of 400 mg/kg for 15 days diminished necrotic death of cardiomyocytes and reduced reperfusion contracture. Ganoderma lucidum extract demonstrated antioxidant properties. The authors believe that the cardioprotective properties of Ganoderma lucidum extract are largely determined by its antioxidant properties.

[On the role of opioid system of myocardium in the implementation of the cardioprotective effect of postconditioning].

Investigated the involvement of the endogenous opioid agonists attack in the implementation of the cardioprotective effect of postconditioning, playing with the model of isolated perfused on Langendorf rat heart. It is established that this phenomenon occurs when using three sessions reperfusion (30 s) and ischemia (30 s) played at the end of the period 45-min global ischemia. Using the selective blocker of different subtypes of opioid receptors, which was added in perfusion solution in early reperfusion period, found that the stability of the heart to action ischemia-reperfusion in ischemic postconditioning is implemented through the activation of the Delta-1 opioid receptor. Suggests that the mechanism cardioproteguoe phenomenon of postconditioning significant role belongs synthesized in the myocardium of endogenous opioids.

Inotropic and chronotropic effects of ischemic postconditioning on the model of isolated heart.

The effects of global ischemia (45 min) and reperfusion (30 min) on left-ventricular developed pressure (LVDP), HR, and end-diastolic pressure were studied on isolated perfused rat heart. The following postconditioning protocols were used: 1) 3 cycles of reperfusion (10 sec) and ischemia (10 sec), total cycle duration 20 sec; 2) 6 cycles reperfusion of reperfusion (10 sec) and ischemia (10 sec), total cycle duration 20 sec; 3) 3 cycles of reperfusion (20 sec) and ischemia (20 sec), total cycle duration 40 sec; 4) 6 cycles of reperfusion (20 sec) and ischemia (20 sec), total cycle duration 40 sec; 5) 3 cycles of reperfusion (30 sec) and ischemia (30 sec), total cycle duration 60 sec. The use of several cycles of a total duration of 20 sec had no effect on LVDP, but reduced EDP throughout the reperfusion period. Postconditioning protocol consisting of three 40-sec cycles promoted LVDP recovery during the reperfusion, but had no effect on EDP and decelerated HP normalization. Six 40-sec cycles had no effect on LVDP and EDP, but impeded HR recovery during the reperfusion period. Postconditioning protocol consisting of three 60-sec cycles promoted LVDP increase during the reperfusion and reduced contracture, but these transient effects were accompanied by decelerated HP normalization.

[The role of sarcolemmal and mitochondrial K(ATP)-channels in realization of the cardioprotection and antiarrhythmic effect of different regimens of hypobaric adaptation].

The aim of study was an investigation of the role of different types of K(ATP)-channels in the increased tolerance to the rat heart to ischemic and reperfusion arrhythmias after the different regimes ofhypoxic adaptation. Wistar rats were exposed to an intermittent hypoxia in two different regimens: 5000 m, 6 h/day during 6 weeks or 7000 m, 8 h/day during 7 weeks. It has been found that both types of adaptation increase cardiac tolerance to arrhythmogenic impact of acute ischemia, but only training at 7000 m induces cardioprotective effect. Inhibition of mitK(ATP)-channels by pretreatment with 5-hydroxydecanoate (5 mg/kg) or MCC-134 (3 mg/kg) completely abolishes cardioprotection and antiarrhythmic effect of adaptation in the 7000 m regimen. Antiarrhythmic effect of adaptation in the 5000 m regimen is eliminated by injection of glibenclamide (0.3 mg/kg), an inhibitor of sarcolemmal and mitochondrial K(ATP)-channels. It has been proposed that in cardioprotection of adaptation in the 7000 m regimen mitK(ATP)-channels play a considerable role, whereas in the 5000 m regimen sarcK(ATP)-channels are involved. Antiarrhythmic effect and cardioprotectio has not been found during experiments on the isolated perfused rat heart.

[Intracellular mechanisms of opioidergic regulation of the myocardial function during normoxia and postischemic reperfusion].

Cardioprotective and inotropic effects of selective agonists of delta1- and k1-opioid receptors (OR): DPDPE (0.1 microM/L) and U-50.488 (0.1 microM/L) were studied during 45 min global ischemia and 30 min reperfusion of the rat isolated perfused heart. Activation of both OR types promoted a 2-fold reduction in reperfusion leakage of creatine kinase. Cardioprotective effect of U-50.488 was accompanied by a 2-fold decrease in cAMP levels in myocardium. The selective delta1-agonist DPDPE had no effect on the cAMP content. Cardioprotective effect of DPDPE was not demonstrated after inhibition of Ca2+-ATPase in sarcoplasmic reticulum (SR) by cyclopiazonic acid. Stimulation of myocardial delta1- and K1-OR decreased the heart rate and force of contraction both before ischemia and during reperfusion. In summary, cardioprotective effect of U-50.488 depends on the reduction in myocardial cAMP levels whereas cytoprotective effect of DPDPE is mediated via opioidergic alteration in Ca2+-transport at SR level. Decrease in pump function of heart in response to OR activation does not depend upon alteration in cAMP levels in the myocardium.

Role of Intracellular Calcium and Cyclic Nucleotides in Realization of Cardioprotective Effects of δ(1)- and κ(1)-Opioid Receptor Agonists.

The role of cyclic nucleotides (cAMP, cGMP) and Ca(2+)-ATPase of the sarcoplasmic reticulum in the mechanism of cardioprotective effects of selective δ(1)- and κ(1)-opioid receptor agonists DPDPE and U-50488 was studied under conditions of global ischemia and reperfusion of isolated and perfused rat heart. Activation of both types of opioid receptors 2-fold reduced the reperfusion release of creatine phosphokinase. The cardioprotective effect of U-50488 was paralleled by a 2-fold decrease in cAMP content in the myocardium, while DPDPE did not modify the content of cAMP throughout the experiment. None of these substances changed the content of cGMP in the myocardium. The cardioprotective effect of DPDPE was not observed after inhibition of sarcoplasmic reticulum Ca(2+)-ATPase with cyclopiazonic acid. The cardioprotective effect of U-50488 was associated with reduction of cAMP level in the myocardium, while the cytoprotective effect of DPDPE was mediated by opioidergic modulation of Ca(2+) transport at the level of the sarcoplasmic reticulum.

[Role of kappa1 opioid receptors and cAMP in regulation of cardiac tolerance to ischemia and reperfusion].

The cardioprotective, inotropic, and antiarrhythmic effects of U-50.488, a selective agonist of kappa1 opioid receptors (kappa1 ORs), was studied using the model of 45-min total ischemia and 30-min reperfusion of isolated rat heart. Cardiac kappa1 ORs were stimulated by adding U-50.488 to the perfusing solution up to the final concentration of 0.1 or 1 micromol/l. The opioid had no influence on the incidence of reperfusion arrhythmias. The addition of 0.1 micromol/l U-50.488 reduced the reperfusion release of creatine phosphokinase (CPK) by half, which positively correlated with the decrease in the myocardial cAMP content (r = 0.89, p < 0.01). At the same time, the addition of U-50.488 in the higher concentration (1 micromol/l) had no effect on either cAMP level or CPK release. These results indicate that the cardioprotective effect of U-50.488 may be connected with the reduction of myocardial cAMP content. Activation of kappa1 ORs caused a decrease in both frequency and amplitude of myocardial contractions. The negative inotropic and chronotropic effect of U-50.488 was shown to be independent of changes in the myocardial cAMP content. A hypothesis is proposed that the absence of any cardioprotective effect of U-50.488 at the higher concentration (1 micromol/l) is accounted for by its interaction with unknown nonopioid receptors of cardiac myocytes.

[Role of kappa1 opioid receptors and cAMP in regulation of cardiac tolerance to ischemia and reperfusion].

Cardioprotective, inotropic, and antiarrhythmic effects of the selective agonist of k1-opioid receptors (k1-ORs) U-50.488H have been studied after 45-min global ischemia and 30-min reperfusion of isolated perfused rat hearts. The heart k1-ORs were stimulated by adding 0.1 or 1 mmol/l U-50.488H to the perfusion solution. The opioid did not affect the frequency of reperfusion arrhythmias. At a concentration of 0.1 mmol/l, it induced a twofold decrease in the reperfusion release of creatine phosphokinase (CPK), which positively correlated with a decrease in the myocardial cAMP level (r = 0.89, p < 0.01). Application of U-50.488H at a final concentration of 1 mmol/l did not change the cAMP level and CPK release. These results suggest that the cardioprotective effect of U-50.488H is due to a decrease in the level of cAMP in cardiomyocytes. Activation of k1-ORs decreased the frequency and force of myocardial contractions. It has been shown that the negative inotropic and chronotropic effects of U-50.488H are independent of changes in the myocardial cAMP level. A hypothesis is proposed that the absence of cardioprotective effect of 1 mM U-50.488H is a result of activation of nonopioid receptors in cardiomyocytes.

[Ganoderma lucidum extract in cardiac diastolic dysfunction and irreversible cardiomyocytic damage in ischemia and reperfusion of the isolated heart].

We used a model of total 45-min ischemia and 30-min reperfusion of isolated rat heart by the Langendorf technique. The course administration (15 days) of Gonoderma lucidum extract attenuated reperfusion contracture and decreased creatine kinase levels in the venous effluent from rat isolated heart during reperfusion. However, the extract did not prevent a reperfusion decrease in pressure developed by the left ventricle, reduction in the heart rate, contraction and relaxation rates. The extract had no effect on the incidence of ventricular arrhythmia. We believe that Ganoderma lucidum extract is a drug which attenuates diastolic dysfunction and prevents irreversible cardiomyocyte damage during ischemia and heart reperfusion.

Activation of kappa-opioid receptor as a method for prevention of ischemic and reperfusion arrhythmias: role of protein kinase C and K(ATP) channels.

Intravenous pretreatment with kappa-opioid receptor antagonist (-)-U-50,488 (1 mg/kg) improved heart resistance to the arrhythmogenic effect of coronary occlusion and reperfusion. Selective kappa1-opioid receptor antagonist norbinaltorphimine and nonselective blocker of peripheral opioid receptors methylnaloxone abolished this antiarrhythmic effect. Preliminary blockade of protein kinase C with chelerythrine or inhibition of ATP-dependent K+ channels (K(ATP) channels) with glybenclamide abolished the antiarrhythmic effect of kappa-opioid receptor activation. Selective inhibitor of sarcolemmal K(ATP) channels did not modulate the kappa-opioid receptor-mediated increase in cardiac electrical stability. Our results suggest that protein kinase C and mitochondrial K(ATP) channels play an important role in the antiarrhythmic effect associated with activation of peripheral kappa-opioid receptors.

Cardioprotective effect of kappa1-opioid receptor activation and role of cAMP in its realization.

The cardioprotective and antiarrhythmic effects of a selective kappa1-opioid receptor agonist U-50,488 were studied during experimental 45-min total ischemia and 30-min reperfusion of isolated rat heart. The opioid had no effect on the incidence and type of reperfusion arrhythmias. U-50,488 in a concentration of 0.1 microM inhibited reperfusion-induced release of creatine phosphokinase and decreased cAMP concentration in the myocardium by 2 times. These parameters remained unchanged after treatment with U-50,488 in a concentration of 1 microM. The cardioprotective effect of U-50,488 was probably associated with a decrease in cAMP concentration in heart cells. U-50,488 in a concentration of 1 microM produced no cardioprotective effect, which can be explained by its interaction with an unknown non-opioid receptor in cardiomyocytes.

Negative inotropic and chronotropic effects of delta-opioid receptor antagonists are mediated via non-opioid receptors.

Ten-minute perfusion of intact isolated rat heart with Krebs-Henseleit solution containing delta-opioid receptor agonists (DPDPE, (-)-TAN-67) or delta-opioid receptor antagonists (naltrindole, TIPP[psi], ICI 174,864) at a final concentration of 0.1 mg/liter decreased HR, blood pressure in the left ventricle, and the rates of myocardial contraction and relaxation. Intravenous injection of delta-agonists (DPDPE, (-)-TAN-67, deltorphin II) or delta-antagonists (naltrindole, TIPP[psi], ICI 174,864) decreased HR in narcotized rats. Naloxone and naltrexone produced no effect on contractility and HR both in vivo and in vitro. Preliminary injection of naloxone and naltrexone did not prevent the negative chronotropic effect of ICI 174,864 in vitro. The negative inotropic and chronotropic effects of delta-opioid receptor antagonists are mediated by unknown non-opioid receptors in the heart.

[Role of kappa-opioid receptors in the regulation of cardiac resistance to arrhythmogenic effects of ischemia and reperfusion].

It was found that pretreatment of rats with selective agonist of kappa1-opioid receptors (OR) (-)--U--50.488 decreased the incidence of ischemic (10 min) and reperfusion (10 min) ventricular arrhythmias. The selective kappa2-OR agonist GR-89696 had no effect on the incidence of ventricular arrhythmias during a 10-min coronary artery occlusion and following reperfusion in anesthetized rats. The effect of (-)--U-50.488 was abolished by the selective kappa1-OR antagonist of non-binaltorphimine and the non-selective peripheral OR antagonist naloxone methiodide. Perfusion of isolated rat heart with (-)--U-50.488 did not affect arrhythmias during ischemia and reperfusion. The authors suggest that stimulation of kappa1-opioid receptors located outside the central nervous system increases heart resistance against arrhythmogenic action of ischemia/reperfusion, antiarrhythmic action of (-)--U-50.488 being mediated through extracardiac opioid receptors.

[Delta-opioid receptor activation prevents appearance of irreversible damages of cardiomyocytes and exacerbates myocardial contractility dysfunction during ischemia and reperfusion].

It is shown that prestimulation of cardiac delta-opioid receptors (OR) by selective agonists (DPDPE and TAN-67) decreases creatine kinase levels in the coronary effluent of isolated rat heart during 45-min global ischemia and 30-min reperfusion. This effect was completely abolished by pretreatment with a delta-antagonist naltrindole or a non-selective agonist naloxone. It was found that preactivation of cardiac delta-OR exacerbates reperfusion contractility dysfunction of the heart. This effect was also eliminated by opioid receptor antagonists. It is suggested that stimulation of cardiac delta-OR prevents irreversible cardiac cell damage but exacerbates contractility dysfunction during ischemia and reperfusion in vitro.

[The effect of stimulation of cardiac delta1-opioid receptors on the resistance of isolated heart to the action of ischemia and reperfusion].

Preliminary stimulation of cardiac delta1-opioid receptors by DPDPE addition at a concentration of 0.1 mg/liter to the perfusion solution decreased the incidence of reperfusion arrhythmias and the reperfusive destruction of cardiac cells. At the same time, the activation of cardiac delta1-opioid receptors resulted in a decrease in myocardial contractility both in the pre-ischemic period and upon restoration of the coronary flow. Pretreatment with naltriondole (a delta-receptor antagonist) or with cyclopiazonic acid (a specific inhibitor of Ca2+ uptake in sarcoplasmic reticulum) completely abolished the antiarrhythmic, cardioprotective, and inotropic effects of DPDPE. It is suggested that the antiarrhythmic, cardioprotective, and inotropic effects of DPDPE is related to the cardiac delta1-opioid receptor activation and Ca2+ transport alteration on the level of sarcoplasmic reticulum.