Experimental Pulmonary Thromboembolism Research Articles

The impact of nebivolol, carvedilol and propranolol on pulmonary microhemodynamics in case of experimental pulmonary thromboembolism in rabbits

BACKGROUND: Beta-adrenoblockers nebivolol, carvedilol and propranolol are used in clinical cardiology for the treatment of patients with ischemic heart disease. Pulmonary thromboembolism can develop in such patients. However, its unknown, what will be the pulmonary microcirculatory changes in case of pulmonary thromboembolism after pretreatment with beta-blockers.
 AIM: The comparative analysis of the pulmonary microhemodynamics changes following experimental pulmonary thromboembolism in rabbits after pretreatment with nebovolol, carvedilol and propranolol.
 MATERIAL AND METHODS: In 35 isolated perfused rabbit lungs we investigated the changes of pulmonary microcirculation in case of experimental pulmonary thromboembolism after pretreatment with 1-blocker nebivolol, combined blocker of 1- and 1, 2-adrenoceptors carvedilol, and blocker of 1, 2-adrenoceptors propranolol.
 RESULTS: After administration of 1, 2-adrenoceptors blocker propranolol and 1-blocker nebivolol the most of the pulmonary microcirculatory parameters increased. Combined 1-, 1, 2-blocker carvedilol caused mainly vasodilatory effects of the pulmonary arterial vessels, however, the pulmonary venous resistance increased. Pulmonary thromboembolism after pretreatment with beta-blockers caused pronounced increase of pulmonary artery pressure, precapillary and pulmonary vascular resistance. In that case after pretreatment with carvedilol capillary filtration coefficient was increased two times more than after propranolol administration; after pretreatment with nebivolol capillary filtration coefficient increased less, than after propranolol administration.
 CONCLUSIONS: Acute pulmonary embolism caused less pronounced increasing of capillary filtration coefficient in case of nebivolol administration, than after pretreatment with carvedilol and propranolol.

Changes of Pulmonary Microhemodynamics in Experimental Pulmonary Thromboembolism after Pretreatment with K-Channel Activators.

Changes in pulmonary microhemodynamics in response to pulmonary embolism under conditions of activation of KATP channels with nicorandil, Kv channels with dapagliflozin, and BKCa channels with Evans blue were studied on isolated rabbit lungs. Under conditions of activation of KATP and BKCa channels, the constrictor reactions of the pulmonary arterial vessels during embolization of the pulmonary artery were less pronounced than in the control. Activation of BKCa channels reduced constrictor reactions of the pulmonary venous vessels, while activation of KATP and Kv channels eliminates them. The shifts of the capillary filtration coefficient are determined to a greater extent by the pre-/postcapillary resistance ratio, than by changes of the endothelial permeability. Pretreatment with dapagliflozin led to a decrease in the capillary filtration coefficient. It was established, that nimesulide exhibits properties of a BKCa-channel activator.

Pulmonary Microcirculation during Experimental Pulmonary Thromboembolism under Conditions of Activation and Blockade of Muscarinic Acetylcholine Receptors.

Changes in pulmonary microcirculation were studied in isolated perfused rabbit lungs during modelling pulmonary thromboembolism under conditions of acetylcholine infusion against the background of treatment with M1 acetylcholine receptor blocker pirenzepine or blockade of muscarinic acetylcholine receptors with atropine. In the first case, the increase in pulmonary artery pressure was less pronounced than in case of atropine treatment. In response to pulmonary embolism after acetylcholine infusion against the background of pirenzepine pretreatment, the capillary hydrostatic pressure and postcapillary resistance did not change, while after atropine treatment, these parameters increased. In case of pulmonary embolism after acetylcholine infusion combined with selective blockade of M1 muscarinic acetylcholine receptors, the capillary filtration coefficient increased to a greater extent, than in the control and after blockade of muscarinic acetylcholine receptors.

Микроциркуляция лёгких при экспериментальной тромбоэмболии лёгочной артерии в условиях активации и блокады М-холинорецепторов

Микроциркуляция лёгких при экспериментальной тромбоэмболии лёгочной артерии в условиях активации и блокады М-холинорецепторов

Role of β3-Adrenoceptor Activation in Changes of Pulmonary Microhemodynamics after Experimental Pulmonary Thromboembolism.

Changes in pulmonary microhemodynamics during modelling of pulmonary thromboembolism against the background of nebivolol and mirabegron pretreatment were studied in isolated perfused rabbit lungs. In both cases, the pulmonary artery pressure and precapillary and pulmonary vascular resistance increased to a greater extent than in control animals, but the increase in capillary hydrostatic pressure was less pronounced. The postcapillary resistance did not change in pulmonary embolism against the background of nebivolol administration and increased in case of mirabegron pretreatment; capillary filtration coefficient after nebivolol pretreatment increased less markedly than after mirabegron administration. The increase in capillary filtration coefficient after activation of β3-adrenoceptors with the specified drugs depended on the ratio of constriction of pulmonary veins, capillary hydrostatic pressure, and endothelial permeability.

Макро- и микрогемодинамика легких при экспериментальной тромбоэмболии легочной артерии в условиях блокады альфа- и бета-адренорецепторов

The pulmonary microhemodynamics changes in the experimental pulmonary thromboembolism model were studied in acute experiments on anesthetized rabbits with isolated dual channels lungs perfusion in control and after the blockade of α-adrenoceptors with phentolamine and β-adrenoceptors with propranolol. In control animals, pulmonary embolism caused the increasing of the pulmonary artery pressure, pulmonary vascular resistance, and precapillary resistance as well as elevating of the capillary filtration coefficient and postcapillary resistance. Phentolamine caused the decrease of the pulmonary artery pressure, pulmonary vascular resistance, and precapillary resistance. After the propranolol injection, the changes in most of the investigated parameters were opposite comparing with their shifts after the blockade of α-adrenoceptors. In the last case, pulmonary thromboembolism caused less increasing of the pulmonary microcirculatory parameters. However, the capillary filtration coefficient was elevated more, then in the control animals. In case of pulmonary thromboembolism after the blockade of the β-adrenoceptors, the most of the hemodynamic parameters increased more, than after the blockade of α-adrenoceptors; in both cases the capillary filtration coefficient increased to the same level. The value of its changes is determined of the reciprocal interaction of the α- and β-adrenergic mechanisms of the regulation of the permeability of the endothelium of the pulmonary vessels.

Inflammatory response and pneumocyte apoptosis during lung ischemia-reperfusion injury in an experimental pulmonary thromboembolism model.

Lung ischemia–reperfusion injury (LIRI) may occur in the region of the affected lung after reperfusion therapy. The inflammatory response mechanisms related to LIRI in pulmonary thromboembolism (PTE), especially in chronic PTE, need to be studied further. In a PTE model, inflammatory response and apoptosis may occur during LIRI and nitric oxide (NO) inhalation may alleviate the inflammatory response and apoptosis of pneumocytes during LIRI. A PTE canine model was established through blood clot embolism to the right lower lobar pulmonary artery. Two weeks later, we performed embolectomy with reperfusion to examine the LIRI changes among different groups. In particular, the ratio of arterial oxygen partial pressure to fractional inspired oxygen (PaO2/FiO2), serum concentrations of tumor necrosis factor-α (TNF-α), myeloperoxidase concentrations in lung homogenates, alveolar polymorphonuclear neutrophils (PMNs), lobar lung wet to dry ratio (W/D ratio), apoptotic pneumocytes, and lung sample ultrastructure were assessed. The PaO2/FiO2 in the NO inhalation group increased significantly when compared with the reperfusion group 4 and 6 h after reperfusion (368.83 ± 55.29 vs. 287.90 ± 54.84 mmHg, P < 0.05 and 380.63 ± 56.83 vs. 292.83 ± 6 0.34 mmHg, P < 0.05, respectively). In the NO inhalation group, TNF-α concentrations and alveolar PMN infiltration were significantly decreased as compared with those of the reperfusion group, 6 h after reperfusion (7.28 ± 1.49 vs. 8.90 ± 1.43 pg/mL, P < 0.05 and [(19 ± 6)/10 high power field (HPF) vs. (31 ± 11)/10 HPF, P < 0.05, respectively]. The amount of apoptotic pneumocytes in the lower lobar lung was negatively correlated with the arterial blood PaO2/FiO2, presented a positive correlation trend with the W/D ratio of the lower lobar lung, and a positive correlation with alveolar PMN in the reperfusion group and NO inhalation group. NO provided at 20 ppm for 6 h significantly alleviated LIRI in the PTE model. Our data indicate that, during LIRI, an obvious inflammatory response and apoptosis occur in our PTE model and NO inhalation may be useful in treating LIRI by alleviating the inflammatory response and pneumocyte apoptosis. This potential application warrants further investigation.

The changes and significance of atrial natriuretic peptide after experimental pulmonary thromboembolism

Objective To compare plasma levels of ANP in experimental and control groups and continuously explore the value of ANP in diagnosis and treatment of acute PTE. Methods Thirty guinea pigs were randomized to PTE group(n = 15) and control( n = 15) group. The plasma level of ANP was examined by radioimmunoassay.Moreover, pulmonary embolism(PE) was explored at dissection and on microscopic examination after PTE. Results (1)The plasma levels of ANP in the early phase of PTE group were significantly higher than those in control group(P＜0.05). (2)The plasma levels of ANP after PTE were significantly higher than those before PTE( P＜0.05). (3)In the late phase of PTE, the plasma levels of ANP in PTE group declined to normal levels, compared with control group, and there was no significant difference( P＞0.05). Conclusion (1) ANP, as a vasodilatory factor,was involved in mechanism of PTE,especially in the early phase of acute PTE. (2)The levels of ANP in plasma played as a sensitive marker used to observe conditions and seriousness of PTE. Key words: Pulmonary embolism; Atrial naturetic factor; Guinea pigs

Influence of L-arginine on the expression of eNOS and COX2 in experimental pulmonary thromboembolism

The influence of L-arginine on endothelial nitric oxide synthase (eNOS) and cyclooxygenase 2 (COX2) was observed in experimental pulmonary thromboembolism and the action mechanism on pulmonary thromboembolism was explored. Wistar rats were randomly divided into control group, model group and treatment group. Pulmonary thromboembolism models were established by auto-blood back transfusion, and L-Arg 100 mg/kg was intraperitoneally injected after successful model preparation. The animals were sacrificed at 3 h, 1 day, 3 days and 7 days after embolism. Plasma NO, TXB2 and 6-Keto-PGFla were detected. The expression of eNOS and COX2 protein and mRNA in pulmonary tissues was detected by immunohistochemistry and RT-PCR respectively. The results showed that pulmonary thrombosis could be seen post pulmonary embolism and inflammatory reaction was significant. Plasma NO was decreased (P<0.01), and the levels of TXB2, 6-Keto-PGF1alpha and T/P ratio were all elevated. The expression of eNOS protein and mRNA in the pulmonary tissue was down-regulated (P<0.05), while that of COX2 protein and mRNA was upregulated (P<0.01). In treatment group, the level of NO was increased, the levels of TXB2 and T/P ratio were decreased, but the level of 6-Keto-PGF1alpha was increased. The expression of eNOS protein and mRNA in pulmonary tissue was upregulated (P<0.05), while that of COX2 protein and mRNA was down-regulated (P<0.05). In conclusion, L-arginine can educe the role of pulmonary tissue protection through up-regulating the expression of intra-pulmonary NOS and down -regulating COX2 in pulmonary thromboembolism.

Thoracic, but not lumbar, epidural anesthesia improves cardiopulmonary function in ovine pulmonary embolism.

We hypothesized that sympathetic stimulation is the main mechanism contributing to hemodynamic failure in pulmonary embolism. We investigated the effects of epidural anesthesia-induced sympathetic blockade, restricted to thoracic and lumbar levels, during pulmonary embolism. Two experiments were performed in chronically instrumented ewes. In the first experiment, six sheep received 6 mL bupivacaine 0.175% (Thoracic Epidural Anesthesia [TEA] group), and six sheep received 6 mL saline 0.9% (TEA-Control group), respectively, via an epidural catheter (T3 level). In the second experiment, six sheep received 2.8 mL bupivacaine 0.375% (Lumbar Epidural Anesthesia [LEA] group), and six sheep received 2.8 mL saline 0.9% (LEA-Control group) epidurally (L4 level). Embolization was performed by IV injection of autologous blood clots (Experiment 1, 0.75 mL/kg; Experiment 2, 0.625 mL/kg). TEA was associated with significantly slower heart rates, decreased mean pulmonary artery pressures and central venous pressures, and significantly higher stroke volume index and oxygenation in comparison with the TEA-Control group. By contrast, LEA was associated with significantly faster heart rates and increased central venous pressures and with a significantly lower stroke volume index in comparison with the LEA-Control group. TEA significantly reduced, and LEA significantly increased, hemodynamic deterioration, suggesting beneficial effects of TEA on cardiopulmonary function during pulmonary thromboembolism. Thoracic (but not lumbar) epidural anesthesia was associated with beneficial cardiopulmonary effects during experimental pulmonary thromboembolism in sheep.

Relation of platelet volume and aggergability

The purpose of this communication is to describe a transient change in platelet volume in relation to a change in its aggregability in an experimental pulmonary thromboembolism in the rabbit.MATERIALS AND METHODSTwenty-five rabbits (5 splenectomized in advance) were catheterized in the bilateral femoral arteries and the central vein under heparin anticoagulation (100U/Kg). The electrocardiogram, respiration, arterial and central venous pressures were recorded throughout the experiment. Adenosine diphosphate (ADP; Sigma) 2 to 5mg/Kg was injected into the central vein in 22 rabbits and saline as a sham procedure in 3 rabbits. Citrated blood samples were obtained before, 30 seconds, 3, 10 and 45 minutes after an injection of either ADP or saline and platelet rich plasma was obtained by centrifugation.Platelet count and volume were measured using a Coulter Counter ZbI coupled with a Channelyser C-1000. An aperture size of 30μ was used and calibration was done using with latex particles. The platelet aggregability was measured by the optical density method as induced by 100μmol of ADP using a Sienco aggregometer. Platelet morphology was studied by a scanning electron microscope (Hitachi S-500).RESULTSWithin several seconds after completion of ADP infusion the animal developed bradycardia, premature beats, ischemic ST-T wave changes, hypotension, bradypnea, apnea and convulsion.Histology of the lung revealed the small arteries to be obstructed with platelet aggregates.Platelet count decreased 30 seconds after and increased 10 minutes after ADP injection (Fig. 1). No significant increase in platelet count was noted in the splenectomized rabbits. A significant increase in platelet volume was noted after ADP injection (Fig. 2, 3). No significant change in platelet shape was noted when its volume showed the maximal change (Fig. 4). Platelet aggregability increased at 3 and 10 minutes after ADP infusion (Fig. 5). When the platelet volume at 10-minute was expressed as the increment from the control value and the aggregability at 10-minute as the increment from the control, the correlation between two deviations was significant (r=0.60, P<0.05(Fig. 6)).COMMENTLarge platelets appeared in the ADP induced pulmonary thromboembolism showed an increase in platelet aggregability and there was a significant correlation between platelet volume and aggregability. This experiment demonstrated that the platelet changes its volume transiently in a certain circumstance in vivo.

ADP-induced experimental pulmonary thromboembolism in spontaneously hypertensive rats (SHR)

Platelets have been known to be an important factor in thrombogenesis. In an early stage of thrombosis, platelets adhere to exposed subendothelial collagen eliciting release of ADP and aggregate each other. ADP seems to be a very important substance in platelet thrombosis. In this experiment ADP was injected into the vein in 7 control Wistar rats and 6 spontaneously hypertensive rats (SHR). SHR were administered with 0.1% NaCl as drinking water over a period of 10 weeks and the blood pressure showed to be 200mmHg or above.ADP 1mg/kg was injected rapidly into the jugular vein of the anesthetized rats. Blood samples were collected from carotid cannula before and 30sec, 3, 10, 20 and 30min after the injection. EKG and respiration were monitered and recorded continuously. 51Cr-labeled platelets were infused in 2 rats. They were sacrificed 1min after ADP injection and the organs were studied for the radioactivity and the histological observation. In control animals, platelet count decreased immediately after the ADP injection. Variable A-V block, premature beats and apnea developed immediately after the injection and subsided by 1min. Arterial hypotension and rise in the central venous pressure were also observed for a period of 10min and gradually subsided. In the analysis of platelet radioactivity, platelets were revealed to accummulate unproportionally in the lungs. Histological examination revealed platelet thrombi in the pulmonary microvas-culature.In SHR rats, decrease in platelet count and heart rate, degree of arrhythmia, apnea, systemic hypotension and elevation in central venous pressure after ADP injection were less than in control rats. In the platelet volume study, the mode related volume was at 2.7μ3 in SHRs as compared with the mode of 2.4μ3 in controls. The volume distribution curve in SHR shifted to the left indicating a relative increase in smaller platelets in the population.In summery, ADP injected into the central vein produced platelet aggregation which were trapped in the pulmonary microvasculature causing pulmonary thromboembolism. Arrhythmia and respiratory distress seems to be due to transient pulmonary thromboembolism. These changes were less severe in SHRs. These results would suggest that hypertension and/or possible association of the vascular change cause different attitude of platelets to ADP.

Location of airway constriction following acute experimental pulmonary thromboembolism.

Location of airway constriction following acute experimental pulmonary thromboembolism.

Pulmonary embolism as a cause of systemic hypotension and shock

Abstract : Experimental pulmonary thromboembolism in dogs supports the clinical observation that severe systemic arterial hypotension and death may result from a relatively small embolus. Severe systemic arterial hypotension, in contrast to pulmonary hypertension, is a variable acute hemodynamic alteration of pulmonary clot embolism. It is theorized that systemic arterial hypotension resulting from pulmonary embolism, exclusive of that caused by the massive pulmonary embolus, is initiated by a vasodepressor response mediated by the vagus and that recovery is dependent in part upon the ability of the peripheral vascular bed to react appropriately with reflex vasoconstriction. The value of the sympathomimetic amines, isoproterenol and metaraminol were assessed in the treatment of postembolic shock. The value of a pressor agent in contrast to one that decreases peripheral vascular resistance is emphasized.