Impact of endothelin-1 in endotoxin-induced pulmonary vascular reactions.

OBJECTIVES: Elevated endothelin-1 (ET-1) levels have been detected during sepsis. The aim of the study was to examine the role of thromboxane A2 (TXA2) and ET-1 in pulmonary vascular reactions after endotoxin (LPS) challenge. DESIGN: Prospective experimental study in rabbits. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Twenty-four adult rabbits of either sex. INTERVENTIONS: Experiments were performed on 30 isolated and ventilated rabbit lungs, which were perfused with a saline solution containing 10% autologous blood. MEASUREMENTS AND MAIN RESULTS: Pulmonary arterial pressure and lung weight gain were continuously registered. Perfusate samples were drawn intermittently to determine ET-1, TXA2, and prostacyclin (PGI2) concentrations. LPS isolated from Escherichia coli (0.5 mg/mL; n = 6) was added to the perfusate. A marked pulmonary arterial pressure increase followed by massive edema formation after 60 mins was observed after LPS injection. At the same time, elevated TXA2 and PGI2 levels in the perfusate were measured. ET-1 was detected 30 mins after LPS infusion (13.4+/-2.6 fmol/L). Pretreatment with the ET(A) receptor antagonist LU135252 (10(-6) M; n = 6) almost completely suppressed the pressure reaction after endotoxin injection (p < .01 at 50 and 60 mins) and reduced edema formation (p < .05). The cyclooxygenase inhibitor diclofenac (10 microg/mL; n = 6) was as effective as LU135252 in preventing vascular reactions after LPS injection. CONCLUSIONS: Pretreatment with the ET(A) receptor antagonist LU135252 and the cyclooxygenase inhibitor diclofenac reduced pulmonary vascular reactions after LPS challenge. Based on the current data, we conclude that the pulmonary arterial pressure increase and edema formation after LPS injection are related to an ET-1- and TXA2-dependent mechanism.

Characterization and distribution of endothelin receptors in the pulmonary circulation: investigation of isolated, perfused, and ventilated rabbit lungs.

The aim of the study was to investigate the distribution of 2 subtypes of endothelin-receptors, mediating the effects of endothelin-1 (ET-1) in the pulmonary circulation. Until now, it is still unclear, whether ET(A) receptors or ET(B) receptors or even both are localized in pulmonary vessels. The experiments were performed on 72 isolated and ventilated rabbit lungs that were perfused with a cell- and plasma-free buffer solution. The arterial pressure and the lung weight gain were continuously registered. Intermittently perfusate samples were taken for determination of thromboxane A2 (TXA2) and prostacyclin (PGI2). The injection of ET-1 (10(-8) M, n = 6) resulted in a biphasic increase in pulmonary arterial pressure (PAP) that was accompanied by the generation of TXA2 and PGI2. Pretreatment with the ET(A)-receptor antagonist LU135252 (10(-6) M, n = 6) suppressed the pressure response after ET-1 application (P < 0.01 at 120 min) and reduced the generation of TXA2 (P < 0.05 at 120 min) and PGI2 (P < 0.05 at 120 min). Pretreatment with the cyclooxygenase inhibitor diclofenac (10 microg/mL; n = 6) also reduced the PAP increase after ET-1 injection. In contrast to this, the pulmonary vascular pressure reaction after ET-1 application was elevated, when ET(B)-receptor antagonist BQ788 (10(-6) M; n = 6) was given. Furthermore, the PGI2 to TXA2 ratio was shifted from 2.3 to 0.9, reflecting a predominance of vasoconstrictive TXA2. The simultaneous application of LU135252 and BQ788 significantly reduced the PAP increase after ET-1 application, but no beneficial effects were observed compared with the application of LU135252 solely. The injection of the ET(B)-receptor agonist sarafotoxin S6c (S6c; 10(-8) M, n = 6) also induced an increase in PAP that was not attenuated by pretreatment with the ET(B)-receptor antagonist BQ788 (10(-6) M, n = 6). LU135252 (n = 6) as well as the application of LU135252 in combination with BQ788 (n = 6) failed to suppress the pressure response after S6c, whereas the cyclooxygenase inhibitor diclofenac (10 microg/mL, n = 6) alone and in combination with LU135252 and BQ788 (n = 6) was able to prevent the PAP increase after S6c injection (P < 0.001). The results demonstrate that the ET-1-induced increase in pulmonary vascular resistance is mainly mediated via ET(A) receptors, whereas ET(B) receptors seem to mediate vasodilation, which was shown by an imbalance of TXA2 and PGI2 generation. On the other hand, the ET(B)-receptor agonist S6c induced vasoconstriction, which was only attenuated by the cyclooxygenase inhibitor diclofenac. From the current results we conclude that, apart from vasoconstrictor ET(A) receptors, at least 2 ET(B)-receptor subtypes are expressed in the pulmonary circulation, one mediating vasoconstriction, which was not blocked by BQ788, and one mediating vasodilation, which was influenced by BQ788.

Alterations of bacterial clearance induced by propofol.

BACKGROUND: The purpose of the study was to investigate the potential influence of the anaesthetic agent propofol on immune function in terms of systemic clearance and organ distribution of injected Escherichia coli in a rabbit model. METHODS: Defined numbers of E. coli (1.3 x 10(8) colony-forming units, CFU) were injected intravenously 1 h after starting a 4-h infusion of the anaesthetic propofol (2 ml.kg-1.h-1, Disoprivan 1%; n = 6)) or after saline application (n = 6). As propofol is formulated in a 10% lipid emulsion, the lipid vehicle Intralipid (2 ml.kg-1.h-1; n = 6) alone was investigated in a separate group. Parameters monitored were arterial pressure and rates of bacterial elimination from the blood. Three hours after bacterial injection, the animals were killed, and tissue samples of liver, spleen, lung, and kidney were collected for microbiological examinations. RESULTS: Compared to saline-treated animals, infusion of propofol induced increased accumulation of E. coli in lung and spleen, thus reflecting reticuloendothelial system dysfunction. CONCLUSION: As the lipid emulsion by itself induced the same effects, the impaired immune function due to propofol is thought to be attributed to its solvent Intralipid.

Endothelin-1 and thromboxane A2 increase pulmonary vascular resistance in granulocyte-mediated lung injury.

OBJECTIVE: To examine the pathophysiologic role of vasoactive eicosanoids and endothelin-1 in granulocyte-mediated effects in the pulmonary vasculature. DESIGN: Prospective experimental study in rabbits. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Thirty adult rabbits. INTERVENTIONS: The experiments were performed on 30 isolated and ventilated rabbit lungs that were perfused with a cell- and plasma-free buffer solution. MEASUREMENTS AND MAIN RESULTS: The pulmonary arterial pressure and the lung weight gain were continuously registered. Intermittently perfused samples were taken to determine endothelin-1 and thromboxane A2 concentrations. Six experiments without intervention served as the sham group. The granulocytes in the pulmonary circulation were stimulated with N-formyl-L-leucin-methionyl-L-phenylalanine (FMLP; 10(-6) M; control, n = 6). To investigate whether activated granulocytes influence the pulmonary vasculature via endothelin-1, the endothelin-A receptor antagonist LU135252 (10(-6) M) was added to the perfusate before FMLP injection (n = 6). The potential involvement of thromboxane A2 in granulocyte-endothelial interaction was investigated by pretreatment with the cyclooxygenase inhibitor diclofenac (10 microg/mL; n = 6). Activation of granulocytes resulted in an acute increase in pulmonary arterial pressure (>9 mm Hg), which was followed by a second delayed pressure increase after 60 mins (>14 mm Hg) and was paralleled by a massive generation of thromboxane A2 (>250 pg/ mL). Fifteen minutes after FMLP-injection, endothelin-1 was detectable in the perfusate. Pretreatment with the selective endothelin-A antagonist LU135252 significantly (p< .01) reduced the initial pressure response after FMLP stimulation, while diclofenac significantly reduced (p < .05) the delayed pressure increase. Using diclofenac (10 microg/mL) in conjunction with LU135252 (10(-6) M; n = 6) before FMLP injection significantly reduced the early and the delayed pressure increase. CONCLUSIONS: Activated granulocytes seem to enhance pulmonary vascular resistance via endothelin-1 and thromboxane A2. The endothelin-1 effects are probably mediated via endothelin-A receptors since the endothelin-A receptor antagonist LU135252 was able to suppress the early pressure reaction after FMLP injection, whereas the cyclooxygenase inhibitor diclofenac was able to reduce the second pressure increase.

The role of endothelin-1 as a mediator of the pressure response after air embolism in blood perfused lungs.

OBJECTIVE: It is well known that lung embolism is associated with an increase in pulmonary vascular resistance. Since the mechanisms of pulmonary vascular reactions during embolism are still unclear, the aim of this study was to investigate the potential involvement of endothelin-1 (ET-1) and thromboxane A2 (TXA2) as mediators of the pulmonary artery pressure (PAP) increase after embolism using the selective ETA receptor antagonist LU135252 [1], the ETB receptor antagonist BQ788 [2], and the cyclooxygenase inhibitor diclofenac. DESIGN: Prospective experimental study in rabbits. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: 36 adult rabbits of either sex. INTERVENTIONS: The experiments were performed in 36 isolated and ventilated rabbit lungs which were perfused with a buffer solution containing 10% of autologous blood. Embolism was induced by the injection of 0.75 ml air into the pulmonary artery. MEASUREMENTS AND RESULTS: PAP and lung weight, reflecting edema formation, were continuously recorded. Perfusate samples were drawn intermittently to determine TXA2 and ET-1 concentrations. Air injection resulted in an immediate increase in PAP up to 22.8 +/- 1.4 mm Hg at 2.5 min (control, n = 6), which was parallelled by an enhanced generation of TXA2. No relevant edema formation occurred during the observation period. Pretreatment with the ETA receptor antagonist LU135252 significantly reduced the pressure reaction after air embolism (p < 0.001) whereas the ETB receptor antagonist BQ788 (n = 6) was without marked effects. The administration of diclofenac (n = 6) did not alter the PAP increase 2.5 min after embolism, but significantly reduced the pressure reaction during the further observation period (p < 0.001). The application of LU135252 and diclofenac together (n = 6) also significantly reduced the PAP increase from 2.5 min during the total observation period (p < 0.001). CONCLUSIONS: The acute pressure reaction after air embolism is mainly mediated via ET-1 by an ETA receptor related mechanism. TXA2 seems to maintain this reaction for a longer time.

Effect of bradykinin B2-receptor antagonism on post-ischemic coronary reperfusion.

Isolated rabbit hearts in a modified Langendorff preparation were used to study the role of bradykinin B2-receptor antagonism on recovery from cardiac ischemia. The experiments were performed to clarify a potential risk of administrating BK-receptor antagonists in patients with coronary heart disease and patients undergoing heart surgery. The hearts were perfused in an open system at a constant pressure of 70 mm Hg and at a constant temperature of 37 degrees C with Krebs-Henseleit-buffer solution containing 6.5% HAES (hydroxyethyl-amylopectin) and 10 mmol Na-pyruvate/l. The perfusate was equilibrated to a PO2 of about 500-600 mm Hg. After a steady state period of 30 min, coronary perfusion was stopped for 30 min and the hearts were subsequently reperfused for further 30 min. Pretreatment with the B2-receptor antagonist, CP-0127, significantly increased (p < 0.001) the coronary vascular resistance during reperfusion from 31.9 +/- 2.1 to 59.0 +/- 6.5 mm Hg/ml/min/10 g wt and decreased the left ventricular pressure amplitude to 44.0 +/- 15.2% (p < 0.005) of it's baseline. When ischemia was combined with hyperkalaemic cardioplegia, CP-0127 did not influence coronary vascular resistance, but depressed, only to a minor degree, left ventricular pressure amplitude to 65.1 +/- 15.4% (p < 0.005) during reperfusion. Arrhythmias during reperfusion with cardiac arrest occurred only in 2 hearts with B2-receptor inhibition when ischemia was not combined with cardioplegia. Dependent on the initial functional status of the heart B2-receptor inhibition impaired recovery from acute coronary ischemia by increasing the coronary vascular resistance and depressing the myocardial function and therefore may constitute a risk in patients undergoing heart surgery and extracorporeal circulation.

Effects of bradykinin, histamine and serotonin on pulmonary vascular resistance and permeability.

The effects of bradykinin, histamine and serotonin on vascular resistance and microvascular permeability were investigated in isolated cell-free perfused rabbit lungs. The capillary filtration coefficient was determined from the slope of lung weight changes over periods of venous pressure elevation before application of bradykinin (n = 6), histamine (n = 6) and serotonin (n = 6), and 5, 20 and 50 min afterwards. To prevent rapid inactivation of bradykinin by the angiotensin-converting enzyme in the pulmonary circulation, the bradykinin effects were additionally studied in the presence of the angiotensin-converting enzyme inhibitor captopril (n = 6). Bolus application of each substance resulted in a short-lasting increase in the pulmonary vascular resistance (3.7-9.1 mmHg). Which was most pronounced in the bradykinin+captopril group. The capillary filtration coefficient was significantly increased after histamine application, and to an even greater extent after serotonin application, whereas bradykinin on its own, as well as bradykinin given in the presence of captopril, had no measurable influence on capillary filtration in the lung. As a result of the bradykinin challenge, there was an immediate massive generation of prostacyclin, which could not be further augmented by a application. Histamine injection entailed a delayed onset of prostacyclin generation after the second stimulation, whereas no prostacyclin increase was measured in the serotonin-treated lungs. Thromboxane A2 generation was exclusively observed after the first serotonin application. The data exemplify different pathophysiological characteristics of bradykinin, histamine and serotonin on lung barrier function. Histamine and serotonin induce oedema formation by enhancing microvascular permeability, whereas bradykinin does not.

Impaired bacterial clearance after activation of the complement and coagulation systems.

The aim of this study was to investigate the influence of the activation of the complement and coagulation systems on bacterial clearance and killing capacity of the reticuloendothelial system in rabbits. To enable quantification of the clearance process, defined numbers of exogenous Escherichia coli (1.3 x 10(8) colony-forming units) were injected intravenously, after complement activation with inulin-activated rabbit serum (n = 6), after complete defibrination with the snake toxin ancrod (n = 6), and in sham-operated animals (controls, n = 6). During the following 180 min observation period, parameters monitored were arterial pressure, fibrinogen, blood gases, and bacterial counts in blood and tissue samples of liver, kidney, spleen, and lung. Defibrination produced a significant delay in blood clearance (p < .05) compared with controls, coupled with up to four times higher bacterial counts in organ homogenates. Complement activation did not affect bacterial elimination kinetics, but was associated with accumulation of E. coli in lung and kidney (up to 100-fold of control values, p < .001). The impaired bacterial clearance associated with increased organ colonization after activation of the complement and coagulation systems reflect reticuloendothelial system dysfunction, thus pointing toward a weaker resistance against bacterial infection.

Alteration of n-3 fatty acid composition in lung tissue after short-term infusion of fish oil emulsion attenuates inflammatory vascular reaction.

OBJECTIVES: To investigate whether modulation of the fatty acid profile can be achieved by the short-term infusion of a fish oil emulsion which may attenuate the pulmonary response to inflammatory stimulation. Changes of fatty acid pattern in-lung tissue and perfusate were analyzed and correlated with physiologic data after a 3-hr infusion of fish oil in comparison with a soybean oil preparation. DESIGN: Prospective, randomized, controlled trial. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Forty standard breed rabbits of either gender. INTERVENTIONS: Isolated lungs from anesthetized rabbits were ventilated and recirculation-perfused (200 mL/min) with 200 mL of cell-free buffer solution to which either 2 mL of saline (control, n = 6), 2 mL of a 10% soybean oil preparation (n = 6), or 2 mL of a 10% fish oil emulsion (n = 6) were added. Samples of perfusate and lung tissue were collected for analysis of fatty acid composition. Tissue and perfusate fatty acid composition were analyzed by capillary gas chromatography. To study metabolic alterations in states of inflammatory stimulation, lungs of each group were stimulated with small doses of the calcium ionophore, A23187 (10(-8) M), during the 180-min lipid perfusion period and again after washing out the lipids by exchanging the perfusion fluid. Pulmonary arterial pressure and lung weight gain were monitored, and eicosanoids were analyzed in the perfusate. MEASUREMENTS AND MAIN RESULTS: Free eicosapentaenoic acids increased several-fold in lung tissue and perfusate during a 3-hr infusion with fish oil. The intravenously administered n-3 fatty acids were rapidly hydrolyzed, as indicated by the appearance of substantial quantities of eicosapentaenoic acid in the perfusate free fatty acid fraction. This increase of perfusion levels of eicosapentaenoic acid was paralleled by an attenuated pressure increase and edema formation due to calcium ionophore challenge and an altered eicosanoid spectrum determined in the perfusate compared with soybean oil-treated lungs. CONCLUSION: Short-term n-3 lipid application (fish oil emulsion) exerts anti-inflammatory effects on lung vasculature, which may be due to the metabolism of eicosapentaenoic acid resulting in the generation of less potent inflammatory eicosanoids.

Effects of N-acetylcysteine on bacterial clearance.

The aim of this study was to investigate whether the oxygen radical scavenger N-acetylcysteine (N-AC) impairs bacterial clearance, thus predisposing the host to increased risk of disease. Blood clearance of Escherichia coli and organ colonization were investigated in anaesthetized rabbits after pretreatment with N-AC (250 mg kg-1 body weight, n = 16) and in sham-operated animals (n = 12). To enable quantification of the clearance process, defined numbers of exogenous E. coli [1.3 x 108 colony-forming units (CFUs)] were injected intravenously. Parameters monitored were kinetics of bacterial elimination from the blood, and polymorphonuclear leucocyte (PMN) oxidative burst activity. Samples of liver, kidney, spleen and lung were collected for bacterial counts. Compared with controls, pretreatment with N-AC resulted in delayed bacterial elimination from blood and higher organ colonization with increased numbers of E. coli in liver, lung and kidney (P < 0.05). N-AC treatment was associated with a suppressed PMN oxidative burst activity. Impaired bacterial clearance and enhanced organ colonization in N-AC-treated animals correlated with reduced oxidative burst activity, suggesting impaired granulocyte-dependent bacterial killing due to N-AC application.

Impairment of bacterial clearance induced by norepinephrine infusion in rabbits.

OBJECTIVE: Purpose of the study was to investigate the potential influence of norepinephrine (NE) on immune functions in terms of systemic and organ-specific bacterial clearance in rabbits. DESIGN: To enable quantification of the clearance process, defined numbers of exogenous Escherichia coli (1.3 x 10(8) CFU) were injected intravenously 60 min after starting the NE infusion at a low dose (1 microgram/kg per min, n = 6), causing an increase (30 mmHg) in mean arterial pressure without affecting the oxygen uptake, and at a higher dose (7.5 micrograms/kg per min, n = 6), resulting in a marked decrease (20%) in oxygen uptake, after infusion of NaCl solution (control, n = 6). In additional experiments (n = 6) NE (1 microgram/kg per min) was tested in endotoxemia induced by simultaneous infusion of endotoxin (40 micrograms/kg per h). Parameters monitored were arterial pressure, oxygen uptake, and rates of bacterial elimination from the blood. At 180 min after E. coli injection, the animals were sacrificed, and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts. RESULTS: NE infusion resulted in a dose-dependent prolonged elimination of the injected E. coli from the blood and in significantly higher (p < 0.05) numbers of CFU in liver and lung compared to the controls. Significant impairment of bacterial clearance was found after shock-producing endotoxemia, whereas simultaneous infusion of NE and endotoxin caused only a slightly delayed blood clearance of the injected bacteria. CONCLUSION: NE dose dependently affected bacterial clearance, which might be due to ischemia-derived hypoxic impairment of the phagocytosis and lysis function of the reticuloendothelial system, whereas NE improved elimination of bacteria in a state of endotoxic shock.

Influence of B2 receptor antagonists on bradykinin-induced vasodilation and edema formation in isolated rabbit hindlimbs.

In search of new possibilities to prevent acute inflammatory vascular reaction, we examined the effect of two selective B2 receptor antagonists, CP 0127 ([Bissuccimidohexane (L-Cys6)-1] and HOE 140 (D-Arg[Hyp3, Thi5, D-Tic7, Oic8]BK), on changes in perfusion pressure and on edema formation caused by bradykinin (BK) in the isolated perfused rabbit hindlimbs. CP 0127 and HOE 140 were added to the perfusion fluid 2 min prior to the first BK-administration (5 x 10(-9) mol/l). A second BK-stimulation was performed after 30 minutes. The antagonists were tested in groups of 6 experiments each at concentrations of 10(-6) mol/l, 5 x 10(-9) mol/l and 10(-10) mol/l. CP 0127 was also tested in a concentration of 10(-8) mol/l. The application of BK resulted in an acute decrease of the mean arterial pressure and in a continual edema formation, reflected by an increase of organ weight (controls, n = 6). Pretreatment with CP 0127 as well as with HOE 140 attenuated dose-dependently the BK-induced vasodilation (p < 0.005) and edema formation. The current results indicate that CP 0127 and HOE 140 are able to reduce BK-induced effects on vascular tone and edema formation.

Effects of stroma-free hemoglobin solutions on pulmonary vascular resistance and mediator release in the isolated perfused rabbit lung.

The aim of this study was to evaluate the effect of an ultrapure bovine stroma-free hemoglobin (SFH) on pulmonary vascular resistance and mediator release and to analyze potential mechanisms of action in the isolated perfused rabbit lung model. Repetitive bolus applications of small amounts of bovine SFH were examined which resulted in a reproducible acute increase of pulmonary vascular resistance of approx. 9 mmHg (controls, n = 6). It was tested whether the platelet-activating factor (PAF) antagonist WEB 2086 (50 microM; n = 6), the cyclooxygenase blocker diclofenac (10 micrograms/ml; n = 6), the iron-chelating agent deferoxamine (500 micrograms/ml, n = 6) and the radical scavenger catalase (5000 U/ml; n = 6) exert a protective effect on vasoconstrictor response to SFH. The pressure increase was completely suppressed in the lungs pretreated with WEB 2086, whereas diclofenac, deferoxamine and catalase failed to inhibit the vasoconstriction due to SFH. No significant differences in either TXB2 generation or in histamine release were found in the WEB 2086 group compared with untreated lungs. The results point towards the crucial role of PAF in mediation of vasoconstrictor side effects due to SFH.

Effect of hypertonic NaCl-starch-solution on oedema of different pathogenesis.

Small volumes of hypertonic NaCl-solutions have been proven to restore haemodynamics in hypovolemic shock patients. Topic of this study was to investigate whether bolus application of 7.5% NaCl-6.5% starch-solution (HSS) apart from its relevance in shock might be an effective therapy in oedema. Considering differential therapeutic aspects, the volume effects of 7.2 ml HSS were tested in three types of oedema: hydrostatic oedema induced by venous congestion (n = 6), oedema caused by bradykinin injection (n = 6), and proteinase-induced oedema (n = 6). The arterial, venous pressure and weight changes indicating volume shifts between intra- and extravascular space were continuously monitored in 36 isolated perfused rabbit hindlimbs. Oedema formation was induced corresponding to a weight gain of 18-20 g. Subsequently 7.2 ml HSS were injected into the extracorporeal circulation system containing 200 ml cell free, isoosmotic perfusate. Six experiments of each oedema group without HSS-application served as controls. 75-100% of oedema formation could be remobilised via bolus application of HSS within 5 min in all types of oedema. A persisting weight reduction was detectable in the hydrostatic and bradykinin oedema, whereas in the elastase oedema the initial weight loss was followed by a regain of weight up to 180% of initial oedema formation at 120 min after HSS-application. The results show that, due to the osmotic gradient induced by bolus application of HSS, the hydrostatic and bradykinin oedema can be permanently remobilised, whereas the therapeutic effect during proteinase oedema is only short-lasting due to an irreversible damage of barrier function.

Modulation of pulmonary vascular resistance and edema formation by short-term infusion of a 10% fish oil emulsion.

BACKGROUND: The aim of this study was to investigate whether the pulmonary response to inflammatory stimulation, resulting in increased vascular resistance and permeability, could be attenuated by short-term infusion of triglycerides containing omega-3 fatty acids. With the concept of altering the composition of membrane phospholipids in such a manner that stimulation resulted in the release of less vasoconstrictive and permeability-enhancing metabolites of eicosapentaenoic acid instead of those of arachidonic acid (AA), the parenteral application of a lipid emulsion prepared from fish oil (Omegavenös) was tested in comparison with a soy oil preparation (Lipovenös). METHODS: Isolated lungs from anesthetized rabbits were ventilated and recirculatingly perfused (200 ml/min) with 200 ml cell-free buffer solution to which either 2 ml saline (controls, n = 6), 2 ml Lipovenös 10% (n = 6) or 2 ml Omegavenös 10% (n = 6) were added. To study the possible metabolic alterations in states of an enhanced AA turnover, lungs of each group were stimulated with smaller doses of A23187 (10(-8) M) during the 180-min lipid perfusion period, followed by a 10 times higher calcium ionophore A23187 (10(-7) M) challenge after washing out the lipids by exchange of perfusion fluid. Pulmonary artery pressure (PAP) and the lung weight gain indicating edema formation were monitored, and eicosanoids were analyzed in samples of the perfusate. RESULTS: Upon A23187 injection lung weight gain and PAP increase were significantly reduced (50%) in Omegavenös-perfused lungs in comparison with controls and Lipovenös treatment. The vascular reactions were accompanied by a shifting from LTC4 to LTC5 during and after Omegavenös perfusion. CONCLUSION: The data demonstrate that omega-3 fatty acids seem to be incorporated into the phospholipid pool of the pulmonary tissue, even after short-term infusion (3 h) resulting in an attenuated pressure reaction and edema formation due to an altered spectrum of metabolites in the case of inflammatory stimulation.

Effects of hemorrhage, hypoxia, and intravascular coagulation on bacterial clearance and translocation.

OBJECTIVE: This study was undertaken to discover if impaired blood clearance functions and killing capacity of the reticuloendothelial system contribute to the high occurrence rate of septic complications after shock, trauma, and thermal injury. DESIGN: Prospective, randomized, controlled trial. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Thirty-three standard-breed rabbits of either sex. INTERVENTIONS: Defined numbers of Escherichia coli (1.3 x 10(8)) colony-forming units were injected intravenously 60 min after induction of hypoxia, standardized by defined reduction of oxygen uptake (60% to 75% of baseline) induced by hypoventilation (n = 6) or hemorrhage (n = 6), after complete defibrination caused by the snake toxin, ancrod (n = 6), and after 60 mins without intervention (controls, n = 6). At 180 mins after bacterial injection, the animals were killed and tissue samples of liver, kidney, spleen, and lung were collected for microbiological examinations. MEASUREMENTS AND MAIN RESULTS: Bacterial elimination from the blood and distribution pattern of viable bacteria in liver, spleen, kidney, and lung were investigated in hemorrhagic, hypoxic, and defibrinated rabbits. Compared with controls, there was a distinct alteration of the elimination kinetics of bacteria from the circulating blood in the experimental groups. First, the initial counts of viable E. coli were up to 300% (p < .05) higher in the defibrination, hemorrhage, and hypoxia groups than in controls. Second, greater numbers of E. coli were found in the blood for a significantly (p < .001) longer period, coupled with up to four times higher counts in organ homogenates in the hemorrhagic and defibrinated groups (p < .01) and more than 100 times higher counts than control values in the hypoxic animals (p < .001). CONCLUSION: Hemorrhage, hypoxia, and intravascular coagulation induce impaired bacterial clearance from the blood that is associated with altered organ distribution patterns, thus reflecting dysfunction of the reticuloendothelial system.

Alterations of bacterial clearance induced by endotoxin and tumor necrosis factor.

The purpose of the study was to investigate the potential influence of endotoxin and tumor necrosis factor (TNF) on immune function in terms of systemic clearance and organ distribution of injected Escherichia coli in a rabbit model. To enable quantification of the clearance process, defined numbers of exogenous E. coli (1.3 x 10(8) CFU) were injected intravenously 60 min after bolus application of TNF (4 x 10(5) U, n = 6), after infusion of endotoxin (40 micrograms/kg of body weight) for 1 h (n = 6) or 4 h (n = 6), or after saline infusion (controls, n = 6). Parameters monitored were arterial pressure, oxygen uptake, and rates of bacterial elimination from the blood. At 180 min after E. coli injection, the animals were sacrificed, and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts. Endotoxin infusion produced a significant delay in blood clearance compared with saline and TNF pretreatment. The diminished systemic bacterial elimination was associated with significantly higher numbers of E. coli in the organs, thus reflecting reticuloendothelial system dysfunction. TNF had no major influence on the elimination kinetics of bacteria but affected the tissue distribution pattern with increased accumulation of E. coli in the lung (up to 100-fold of control values; P < 0.001).

Influence of a pentoxifylline-analogue on the granulocyte-mediated pulmonary mediator release and vascular reaction.

The influence of a novel pentoxifylline-analogue, HWA 138, on the polymorphonuclear neutrophil leukocyte (PMN)-mediated changes in pulmonary resistance and mediator release was investigated in the isolated perfused and ventilated rabbit lung model. Isolated, washed human granulocytes were injected into the pulmonary artery and stimulated by either 10(-6) mol/L N-formyl-L-leucin-methionyl-L-phenylalanine (FMP) or 3 x 10(-8) mol/L phorbol 12-myristate 13-acetate (PMA) in the presence or absence (controls) of HWA 138 (10(-4) mol/L). Shortly after granulocyte activation, there was a massive generation and release of thromboxane (> 110 pg/ml) and histamine (150-400 nmol/L), with an acute increase of pulmonary artery pressure (> 8 mmHg) in the control groups. Application of HWA 138 almost completely suppressed mediator formation and release as well as pulmonary vascular reaction in the FMP stimulated group. In contrast to this, HWA 138 was unable to influence either mediator release, the pulmonary pressure reaction or interstitial edema formation following PMA stimulation. In the present model, HWA 138 is supposed to be effective via granulocytes by decreasing mediator release, obviously due to burst reaction.

Experimental studies of the influence of priming solutions on the systemic activation of complement during cardiopulmonary bypass: comparison between the use of albumin, hydroxyethyl starch and HWA-138.

Cardiopulmonary bypass surgery may be complicated by a systemic inflammatory reaction, which has been ascribed to activation of complement. For such activation, the choice of priming solution for the heart-lung machine may be of importance. The peripheral blood of three groups of eight donors was exposed to albumin, hydroxyethyl starch (HES) or to HWA-138 (pentoxifylline analogue) in addition to the priming solutions. The study confirmed that activation of complement is a consistent phenomenon during cardiopulmonary bypass surgery. The concentration of the C3 activation product C3a in the plasma was significantly increased after simulated extracorporeal circulation. However there were no differences within the increase of C3a concentrations between the various priming solutions.