Effect of omentin on cardiovascular functions and gene expressions in isolated rat hearts.

OBJECTIVE: Omentin is a recently identified novel adipocytokine mainly expressed in the epicardial adipose tissue. Although it has favorable effects on cardiovascular disease, the impact of omentin on the hearts is still an understudied issue. The aim of the present study was to investigate the possible effects of omentin on isolated rat heart. METHODS: Using the Langendorff method, 28 adult male Sprague-Dawley rat hearts were isolated and perfused with modified Krebs-Henseleit solution (mK-Hs). Concentrations of 100, 200, and 400 ng/mL omentin were given to the hearts for 30 min. The control group (n=7) was perfused with mK-Hs alone. Gene expressions in the left ventricle tissue were determined by real-time polymerase chain reaction. Left ventricular cyclic adenosine monophosphate and cyclic guanosine monophosphate (cGMP) concentrations were determined by using enzyme-linked immunosorbent assay. RESULTS: All concentrations of omentin significantly decreased left ventricular developed pressure and maximal rate of pressure development that are the indexes of cardiac contractility. At the same time, omentin decreased both phosphoinositide 3-kinase γ (PI3Kγ) and sarcolemmal L-type Ca2+ channel (CaV1.2) mRNA levels. Moreover, this peptide at concentrations of 200 and 400 ng/mL increased endothelial nitric oxide synthase (eNOS) mRNA. Furthermore, concentrations of 200 and 400 ng/mL omentin increased the amount of cGMP. CONCLUSION: We conclude that acute omentin treatment decreases cardiac contractility. Elevated eNOS mRNA and cGMP levels with reduced CaV1.2 mRNA are likely to lead to negative inotropy.

The Effect of Chemerin on Cardiac Parameters and Gene Expressions in Isolated Perfused Rat Heart

Background: Chemerin is a novel chemoattractant adipokine expressed in cardiovascular system, and its receptor has been detected in the epicardial adipose tissue. Aims: To determine the effects of chemerin on the cardiac parameters and gene expressions in the isolated perfused rat heart. Study Design: Animal experiment. Methods: The hearts were retrogradely perfused with Langendorff technique to measure the cardiac parameters. The experimental groups were acutely treated with 10, 100, and 1000 nM doses of chemerin. Another group was given 10 µM L-nitric oxide synthase inhibitor for 5 min before 1000 nM chemerin administration. The real-time polymerase chain reaction was performed for detecting the expression of target genes. Results: All doses of chemerin significantly decreased the left ventricular developed pressure (max 35.33 Δ%, p<0.001), and +dP/dtmax (max 31.3 Δ%, p<0.001), which are the indexes of cardiac contractile force. In addition, 1000 nM chemerin reduced the coronary flow (max 31 Δ%, p<0.001). N(W)-nitro-L-arginine methyl ester antagonized the negative inotropic effect of chemerin on contractility. Chemerin induced a 2.16-fold increase in endothelial nitric oxide synthase mRNA and increased the cyclic guanosine monophosphate levels (p<0.001) but decreased the PI3Kγ gene expression (1.8-fold, p<0.001). Furthermore, all doses of chemerin decreased the CaV1.2 gene expression (1.69-fold, p<0.001). Conclusion: Acute chemerin treatment induces a negative inotropic action with the involvement of nitric oxide pathway, CaV1.2, and PI3Kγ on isolated rat heart.

The Effects of Beta Amyloid Peptide 1-42 on Isolated Rat Hearts and Ileum Smooth Muscle.

Neurotoxic beta amyloid peptides (ßAPs) are involved in the pathogenesis of Alzheimer disease. ßAP1-42 may also play a role in the regulation of cardiovascular functions. Therefore, we investigated the possible effects of ßAP1-42 on isolated rat heart and ileum. The hearts were perfused with modified Krebs-Henseleit solution. Left ventricular developed pressure (LVDP), maximal rate of pressure development of left ventricle (+dP/dtmax), heart rate, coronary flow, monophasic action potential amplitude (MAPamp), MAP duration at 90% repolarization (MAP90) and contractions of ileum were measured. One, 10 and 100 nmol/l doses of ßAP1-42 significantly decreased LVDP, +dP/dtmax and heart rate. The dose of 1 nmol/l did not change coronary flow, but 10 and 100 nmol/l doses significantly reduced it. All doses of ßAP1-42 did not alter MAPamp, but increased MAP90. ßAP1-42 (1, 10, 100, 1,000 nmol/l) also did not influence ileum contractions. We suggest that ßAP1-42 produces negative inotropic and negative chronotropic effects with an increase in MAP duration. Furthermore, ßAP1-42 at high doses decreases coronary flow.

Effects and mechanisms of curcumin on the hemodynamic variablesof isolated perfused rat hearts.

BACKGROUND/AIM: There is no information on the dose-response relationship of curcumin on the hemodynamic variables of the heart at the organ level in isolated perfused rat hearts. We aimed to investigate the effects and mechanisms of curcumin on the hemodynamic variables of isolated perfused rat hearts. MATERIALS AND METHODS: Rats were randomly divided into 9 groups. The isolated rat heart was retrogradely perfused with modified Krebs-Henseleit solution. After the stabilization period, each group was administered one of the following treatments for 25 min: saline, dimethyl sulfoxide, and curcumin (0.2 µM, 1 µM, and 5 µM); atropine (1 µM); atropine (1 µM) + curcumin (1 µM); L-NAME (100 µM); or L-NAME (100 µM) + curcumin (1 µM). Hemodynamic variables of the heart were measured. RESULTS: Curcumin at dose of 1 µM decreased the heart rate (from 271 ± 11.1 to 200.4 ± 14.3 beats/min, P = 0.011) but increased end-diastolic pressure (from 7.0 ± 0.4 to 54.6 ± 7.9 mmHg, P = 0.0008). A dose of 5 µM curcumin caused a decrease in the developed pressure (from 87.58 ± 9.0 to 65.40 ± 7.0 mmHg, P = 0.047) but an increase in the end-diastolic pressure (from 6.8 ± 0.6 to 48.9 ± 7.7 mmHg, P = 0.005). Atropine (1 µM) reversed the effects of curcumin on the heart. CONCLUSION: Our results suggest that curcumin produces dose-dependent negative chronotropic and inotropic effects in isolated perfused rat hearts.

Amyloid beta peptide 22-35 induces a negative inotropic effect on isolated rat hearts.

Evidences indicate that deposition of amyloid beta peptides (Aßs) plays an important role in the pathogenesis of Alzheimer disease. Aßs may influence cardiovascular system and ileum contractions. But the effect of amyloid beta peptide 22-35 (Aß22-35) on cardiovascular functions and contractions of ileum has not been studied. Therefore, the present study aimed to investigate the possible effects of this peptide on isolated rat heart and ileum smooth muscle. Langendorff-perfused rat heart preparations were established. The hearts were perfused under constant pressure (60 mmHg) with modified Krebs-Henseleit solution. Aß22-35 at doses of 1, 10 and 100 nM significantly decreased left ventricular developed pressure (LVDP; an index of cardiac contractility) and maximal rate of pressure development of left ventricle (+dP/dtmax; another index of cardiac contractility). This peptide at doses studied had no significant effect on heart rate, coronary flow, monophasic action potential amplitude (MAPamp), MAP duration at 90% repolarization (MAP90) and ileum contractions. We suggest that Aß22-35 exerts a negative inotropism on isolated rat hearts with unchanged heart rate, coronary flow, MAPamp, MAP90 and smooth muscle contractility of ileum.

Positive inotropic, positive chronotropic and coronary vasodilatory effects of rat amylin: mechanisms of amylin-induced positive inotropy.

Even though there are a few studies dealing with the cardiac effects of amylin, the mechanisms of amylin-induced positive inotropy are not known well. Therefore, we investigated the possible signaling pathways underlying the amylin-induced positive inotropy and compared the cardiac effects of rat amylin (rAmylin) and human amylin (hAmylin).Isolated rat hearts were perfused under constant flow condition and rAmylin or hAmylin was infused to the hearts. Coronary perfusion pressure, heart rate, left ventricular developed pressure and the maximum rate of increase of left ventricular pressure (+dP/dtmax) and the maximum rate of pressure decrease of left ventricle (-dP/dtmin) were measured.rAmylin at concentrations of 1, 10 or 100 nM markedly decreased coronary perfusion pressure, but increased heart rate, left ventricular developed pressure, +dP/dtmax and -dP/dtmin. The infusion of H-89 (50 µM), a protein kinase A (PKA) inhibitor did not change the rAmylin (100 nM)-induced positive inotropic effect. Both diltiazem (1 µM), an L-type Ca2+ channel blocker and ryanodine (10 nM), a sarcoplasmic reticulum (SR) Ca2+ release channel opener completely suppressed the rAmylin-induced positive inotropic effect, but staurosporine (100 nM), a potent protein kinase C (PKC) inhibitor suppressed it partially. hAmylin (1, 10 and 100 nM) had no significant effect on coronary perfusion pressure, heart rate and developed pressure, +dP/dtmax and -dP/dtmin.We concluded that rAmylin might have been produced vasodilatory, positive chronotropic and positive inotropic effects on rat hearts. Ca2+ entry via L-type Ca2+ channels, activation of PKC and Ca2+ release from SR through ryanodine-sensitive Ca2+ channels may be involved in this positive inotropic effect. hAmylin may not produce any significant effect on perfusion pressure, heart rate and contractility in isolated, perfused rat hearts.

Effects of proadrenomedullin N-terminal 20 peptide and calcitonin on isolated perfused rat hearts.

OBJECTIVE: There are evidences that proadrenomedullin N-terminal 20 peptide (PAMP) and calcitonin may be involved in cardiovascular function. Therefore, we studied effects of rat PAMP and human PAMP as well as rat calcitonin and salmon calcitonin on coronary perfusion pressure, heart rate and contractile force. METHODS: Isolated rat hearts were perfused under constant flow condition and rat PAMP (1.10 and 100 nM), human PAMP (1,10 and 100 nM), rat calcitonin (10.100 and 1000 nM) or salmon calcitonin (10.100 and 1000 nM) were infused to the hearts. Coronary perfusion pressure, heart rate, left ventricular developed pressure and +dP/dtmax were measured. Statistical analysis was performed using repeated measures ANOVA and Bonferroni posthoc tests. RESULTS: Rat PAMP (1.10 and 100 nM) did not alter perfusion pressure. However, it increased heart rate from 257.83+/-23.89 to 282+/-24.98 beats/min (p<0.001), from 259.83+/-25.05 to 289.8+/-19.5 beats/min (p<0.001) and from 249.66+/-19.19 to 280.50+/-25.26 beats/min (p<0.001) for 1.10 and 100 nM, respectively. Rat PAMP decreased left ventricular developed pressure from 90.5+/-18.5 to 79+/-15.3 mmHg (p<0.05), from 88.00+/-10.12 to 73.00+/-12.38 mmHg (p<0.05) and from 79.83+/-8.98 to 64.83+/-10.12 mmHg (p<0.05) for 1.10 and 100 nM, respectively. The peptide also decreased +dP/dtmax from 3710.5+/-370.6 to 3223.8+/-261.1 mmHg s-1 (p<0.001), from 3683.16+/-327.27 to 3040.6+/-423.8 mmHg s-1 (p<0.01) and from 3746.16+/-315.76 to 3009.83+/-204.64 mmHg s-1 (p<0.001) for 1.10 and 100 nM, respectively. Rat calcitonin (10.100 and 1000 nM) did not change perfusion pressure but it decreased heart rate from 269.16+/-22.6 to 253.6+/-22.84 beats/min (p<0.05), from 263.8+/-27.3 to 247.00+/-36.63 beats/min (p<0.05) and from 285.0+/-32.4 to 264.00+/-39.83 beats/min (p<0.01) for 10.100 and 1000 nM, respectively. Rat calcitonin did not significantly affect left ventricular developed pressure. Human PAMP or salmon calcitonin did not change perfusion pressure, heart rate and left ventricular developed pressure. CONCLUSION: We conclude that rat PAMP may induce positive chronotropic and negative inotropic effect while rat calcitonin may produce a negative chronotropic effect. Human PAMP or salmon calcitonin could not alter perfusion pressure, heart rate and contractility in isolated, perfused rat hearts.

Dietary polyphenol quercetin protects rat hearts during reperfusion: enhanced antioxidant capacity with chronic treatment.

OBJECTIVE: Quercetin is an important member of dietary flavonoid family and widely present in red wine and Mediterranean diet. The major objective of the this study is to evaluate the beneficial effects of quercetin in protecting the myocardium from the deleterious effects of ischemia reperfusion (I/R) injury in chronic quercetin treatment with or without an acute quercetin infusion protocols. METHODS: Forty male Sprague-Dawley rats were included in this experimental randomized study/ Langendorff perfused isolated rat hearts were subjected to 60-min of global ischemia period following 60-min of reperfusion. All animals were randomly divided into 4 groups. Group 1 animals were kept as controls. Group 3 and 4 animals received 50 mg/kg quercetin via an intragastric tube for 7 days for chronic treatment. Group 2 and 4 animals received an acute 15 mmol/L infusion for 30 minutes before the onset of ischemia. The myocardial postischemic recovery was compared using hemodynamic data (peak systolic pressure, end-diastolic pressure and +dP/dtmax), coronary flow, biochemical parameters (lactate dehydrogenase, creatine kinase-MB fraction, cardiac troponin I) from coronary effluent, and oxidative stress markers (malondialdehyde, glutathione, glutathione reductase and nitrite) from heart tissue homogenates in each group. RESULTS: Quercetin has provided increased preservation in myocardial recovery in both chronic and acute treatment protocols compared to non-treated group. According to all estimated hemodynamic parameters, while the statistical difference between acute treated hearts and control hearts was significant (p<0.05); this significance was more clear in chronic treated groups (group 3 and 4) when compared to control (p<0.01). Likewise, biochemical and oxidative stress markers displayed significant differences in acute treated and chronic treated hearts when compared to control (p<0.05 and p<0.01, respectively). CONCLUSION: As a major dietary flavonoid, due to its antioxidant and cytoprotective actions, quercetin has the capacity to protect the myocardial tissue against global ischemia and reperfusion injury. In instances where the molecule is administered for the purpose of acute therapy, this cardioprotective effect of a significant degree can be observed to; however, this potency is further accentuated upon administration as a chronic treatment protocol for seven days.

Effects of tramadol on myocardial ischemia-reperfusion injury.

OBJECTIVES: The aim of the present study was to evaluate the effect of tramadol on isolated rat hearts subjected to global ischemia-reperfusion injury. DESIGN: Langerdorff perfused isolated rat hearts were subjected to 60 min of global ischemia following 60 min of reperfusion. In group I and III hearts were received tramadol before the onset of ischemia. Following the ischemic period, group II and III hearts were received tramadol infusion. Group I and IV hearts were subjected to saline at the same time point. The myocardial postischemic recovery was compared using hemodynamic, coronary flow, biochemical parameters from coronary effluent, and oxidative stress markers from heart tissue homogenates. RESULTS: There were significant differences between tramadol and saline used groups in hemodynamic parameters. GPx values of groups I and III were significantly lower than group IV (p<0.05). SOD values of groups I, II and III were higher than group IV (p<0.05). LDH values of groups I and II were significantly lower than groups III and IV (p<0.05). CONCLUSION: Tramadol provides a cardioprotective effect against myocardial ischemia-reperfusion in isolated rat heart.

Protective effects of resveratrol in ischemia-reperfusion injury of skeletal muscle: A clinically relevant animal model for lower extremity ischemia.

Ischemia and reperfusion injury of the skeletal muscle is a common and serious condition observed in patients admitting to peripheral vascular surgery, interventional radiology and cardiology departments. Resveratrol (RVT) being a strong natural antioxidant is found in deal of red wine and Mediterranean diet. In the present study, male Spraque-Dawley rats were randomized into two groups of equal size. The first group was the control group, and these rats were administered with tap water with a gastric tube for fourteen consecutive days once daily. According to the same protocol, the rats in the second group were treated with tap water containing 20 mg/kg RVT. All the rats in the two groups were subjected to acute hind limb ischemia through clamping of the abdominal aorta for 120 min. Following this procedure, 60 minutes of reperfusion was applied by reestablishing blood flow in both iliac arteries. Ischemic damage in the skeletal muscle tissue was assessed by measuring myoglobin, lactate dehydrogenase, creatinine phosphokinase, aspartate transaminase enzymes in venous blood samples obtained at the end of the reperfusion period. Oxidative stress caused by reperfusion was determined by measuring MDA, carbonyl and protein sulphydryl levels in quadriceps muscle tissue retrieved at the end of the experiment. In Group II rats, all the measured ischemic enzymes and the markers of oxidative stress reflected robust anti-ischemic properties obtained by RVT administration. The data from both groups revealed statistically significant protection against acute skeletal muscle ischemia and reperfusion injury in Group II rats, compared to Group I. As a major dietary flavonoid RVT can protect the skeletal muscle tissue against global ischemia and reperfusion injury because of its strong antioxidant and cytoprotective properties.

The effects of dopexamine in bupivacaine and ropivacaine induced cardiotoxicity in isolated rat heart.

OBJECTIVE: To compare the inotropic and chronotropic effects of ropivacaine and bupivacaine in an isolated, spontaneously beating rat heart, and to determine the reversal effects of dopexamine on these effects. METHODS: The study was conducted at the Department of Physiology, Medical Faculty, Osmangazi University, Eskisehir, Turkey in November 2001. Fifty animals were randomly assigned to 5 groups. Hearts were perfused with a modified Krebs Henseleit solution. In group I (n=10) hearts were exposed to bupivacaine 5 x 10-6 M and in group II (n=10) hearts were exposed to ropivacaine 5 x 10-6 M for 15 minutes. Group III (n=10) was the dopexamine control group and hearts were exposed to dopexamine 1 x 10-6 M for 5 minutes. In group IV (n=10) and in group V (n=10) hearts were exposed to dopexamine in 1 x 10-6 M doses immediately after the bupivacaine and ropivacaine infusions. Heart rates and contractile forces were recorded continuously during the study. RESULTS: Both of the local anesthetics had cardiac depressant effect on isolated hearts. Bupivacaine created more significant effect on heart rate and contractility than ropivacaine. Hearts receiving dopexamine after the infusion of local anesthetic, recovered more quickly. CONCLUSION: Bupivacaine had more depressant effects on cardiac contractility and chronotropy than ropivacaine. Dopexamine may provide an alternative to presently recommended pharmacological therapy in cases of bupivacaine and ropivacaine induced cardiotoxicity. But, the clinical impact of the use of dopexamine in this situation deserves further evaluation.

Erythropoietin changes contractility, cAMP, and nitrite levels of isolated rat hearts.

There is enough evidence that erythropoietin (EPO) may be involved in cardiovascular function. Therefore we have investigated the possible effects of EPO on left ventricular developed pressure, +dP/dt(max), heart rate, tissue cAMP, and nitrite levels. Isolated rat hearts were perfused under constant flow (10 ml/min) conditions with modified Krebs-Henseleit solution and recombinant human erythropoietin at doses of 100, 200, 500, and 1,000 IU/kg was administered as bolus injections. EPO at 100 IU/kg decreased, but higher doses (500 and 1,000 IU/kg) raised the developed pressure and +dP/dt(max). However, it did not affect heart rate or coronary perfusion pressure when all the respective doses were applied. EPO at 100 IU/kg increased nitrite, and at 1,000 IU/kg it raised cAMP. Our results suggest that EPO may produce dose-dependently negative and positive inotropic effects on myocardial contractility in isolated rat hearts. NO and cAMP may be involved in negative and positive inotropic effects of EPO, respectively.

Trimetazidine-induced enhancement of myocardial recovery during reperfusion: a comparative study in diabetic and non-diabetic rat hearts.

BACKGROUND: Diabetes mellitus (DM) is a major predisposing factor for ischemic heart disease. Metabolic disturbances in diabetic heart including impaired myocardial glucose uptake and elevated plasma free fatty acids and increased rate of fatty acid beta-oxidation are probably important contributing factors to greater mortality. Trimetazidine (TMZ), a well-studied anti-ischemic agent, has been demonstrated to be beneficial in treatment of coronary artery disease as well as in treatment of diabetic patients. However, studies reporting the effects of the drug against global myocardial ischemia/reperfusion injury, particularly in diabetic hearts, are rare. This study was mainly aimed to investigate the cardioprotective action of TMZ against global ischemia in diabetic hearts and to compare its protective efficiency level with non-diabetics. METHODS: Twenty streptozotocin-induced diabetic and 20 non-diabetic rats were divided into two groups each. Group I (diabetic, n = 10) and group III (non-diabetic, n = 10) rats were given saline in both pretreatment and acute treatment protocols and reserved as control groups. Group II (diabetic, n = 10) and group IV (non-diabetic, n = 10) rats were both pretreated orally with 3 mg/kg TMZ twice daily for 5 days and treated with TMZ infusion at a concentration of 10(-6) M for 30 min during the experiment. Isolated hearts from each rat were submitted to Langendorff perfusion and a period of 60 min of global ischemia following 60 min of reperfusion. Myocardial post-ischemic recovery was compared in each group using hemodynamic data (peak systolic pressure, end diastolic pressure, +dP/dt(max)), coronary flow, biochemical parameters (CK-MB, cTnT) from coronary effluent, and obtained data were statistically analyzed by both MANOVA and two-sample Hotelling's T2 tests. RESULTS: Both hemodynamic and biochemical findings signaled a significantly enhanced myocardial recovery provided by TMZ treatment in diabetic and non-diabetic hearts as compared to non-treated hearts. Although efficiency level of TMZ on mechanical recovery was not different between diabetics and non-diabetics, the protective action of TMZ on myocardial damage measured by biochemical parameters was more evident in diabetic hearts than in non-diabetics. CONCLUSIONS: Shifting myocardial energy metabolism away from fatty acids toward glucose oxidation and regulating transmembrane ion disturbances by TMZ can be considered as an appropriate adjunctive treatment in diabetics, especially in patients undergoing open-heart surgery who will be exposed to global myocardial ischemia.

Cardiorespiratory responses to submaximal incremental exercise are not affected by one night's sleep deprivation during the follicular and luteal phases of the menstrual cycle.

The purpose of the study was to investigate the effects of one night's sleep deprivation on the cardiorespiratory responses to exercise during the follicular and luteal phases of the menstrual cycle. We have studied nine, healthy females aged 24-35 years with regular menstrual cycles. Each subject performed spirometric tests at rest and then an incremental exercise testing during 11-13 days of follicular phase and 22-24 days of luteal phase following one normal night's sleep or one night's sleep loss. Compared with resting values exercise produced significant increases in cardiorespiratory variables including oxygen uptake (VO2), carbon dioxide production (VCO2), tidal volume (VT), respiratory rate (RR), minute ventilation (VE), systolic blood pressure, heart rate (HR) and respiratory quotient (R). However, it did not alter significantly diastolic blood pressure, end-tidal PO2 (PETO2), end-tidal PCO2 (PETCO2) and arterial oxygen saturation (SaO2). Spirometric variables which include forced vital capacity (FVC), forced expiratory volume in one s (FEV1), FEV1/FVC%, forced expiratory volume in three s (FEV3), forced expired flow from 25-75% of FVC (FEF 25-75%), forced expired flow at 25% of FVC (FEF 25%), forced expired flow at 50% of FVC (FEF 50%), forced expired flow at 75% of FVC (FEF 75%), forced expired flow from 75-85% of FVC (FEF 75-85%), peak expiratory flow (PEF), expiratory reserve volume (ERV), inspiratory capacity (IC) and maximal voluntary ventilation (MVV) and cardiorespiratory variables were not different between the cycle phases after one normal night's sleep or one night's sleep deprivation. Neither menstrual cycle phase nor sleep deprivation affected spirometric and cardiorespiratory parameters. We suggest that one night's sleep deprivation does not produce alterations in spirometric parameters and cardiorespiratory responses to submaximal incremental exercise during the follicular and luteal phases.