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S Zahler

Publications and source records attributed to S Zahler.

At least 37 records · Page 2Linked to original sources
PubMed1999

Indirect enhancement of neutrophil activity and adhesion to cultured human umbilical vein endothelial cells by isoprostanes (iPF2alpha-III and iPE2-III).

Isoprostanes are metabolites of arachidonic acid found in blood under various conditions of oxidative stress. Because arachidonic acid derivatives are major mediators of inflammation, we investigated the potential inflammatory effects of iPF2alpha-III (previously 8-isoPGF2alpha) and iPE2-III (8-isoPGE2) on human polymorphonuclear granulocytes (PMN), as well as on human umbilical vein endothelial cells (HUVECs). The early activation marker CD11b on PMN and the adhesion molecules ICAM-1, E-selectin, and P-selectin on HUVECs were quantified by flow cytometry. Levels of the cytokines interleukin (IL)-6 and IL-8 were measured in the culture supernatant by enzyme-linked immunosorbent assay. Furthermore, adhesion of PMN to HUVECs was assessed. Neither isoprostane showed any direct stimulatory effects on PMN or HUVECs at concentrations of 0.1 or 1 microM: there was no acute elevation in expression of CD11b or P-selectin and no change of ICAM-1 or E-selectin after 4 or 24 h of incubation, respectively. The levels of interleukin IL-6 and IL-8 were also unaltered. However, PMN adhesion was significantly enhanced both after 4 and 24 h of incubation of HUVECs with iPF2alpha-III, and CD11b expression on PMN was elevated by contact of these cells with the supernatant of pre-exposed HUVECs. Neither of these actions were inhibited by an endothelin receptor antagonist (bosentan) or a combined thromboxane A2/isoprostane-receptor antagonist (SQ29548). Thus, although not having a direct pro-inflammatory potential, isoprostanes might indirectly accentuate PMN stimulation. This seems to occur via a receptor-independent mechanism, perhaps the production of an active metabolite of isoprostanes by endothelial cells.

Cell Adhesion↗
PubMed1999

Ketamine does not inhibit inflammatory responses of cultured human endothelial cells but reduces chemotactic activation of neutrophils.

BACKGROUND: Ketamine is a widely used general anaesthetic, which has been reported to inhibit neutrophil function and neutrophil-endothelial interaction. To date, however, it is unknown whether ketamine has any direct effects on endothelial cells with respect to inflammation. Therefore, we investigated the influence of varying concentrations of ketamine (0.5, 1, and 3 microM) on the endothelial expression of cytokines and adhesion molecules with relevance for inflammation. METHODS: Cultured human umbilical vein endothelial cells were stimulated with tumor necrosis factor alpha (TNFalpha, 2.5 ng/ml) for 4 h in the absence or presence of ketamine. The adhesion molecules ICAM-1 and E-selectin on the endothelial cells were measured by flow cytometry. Release of the proinflammatory cytokines IL-6 and IL-8 by endothelial cells was quantified by ELISA. The acute effect of ketamine on leukocyte activation by the supernatant of endothelial cells pre-stimulated with TNFalpha (4 h) was tested by flow cytometric measurement of CD11b, a leukocyte activation marker, after 15 min of coincubation. RESULTS: TNFalpha caused dramatic upregulation of both adhesion molecules (15-fold and 5-fold vs. control for ELAM-1 and ICAM-1, respectively) and of both cytokines (500-fold and 1.8-fold for IL-6 and IL-8, respectively). No concentration of ketamine employed in our study had any effect on these inflammatory parameters. However, activation of leukocytes by supernatant of TNFalpha-conditioned endothelial cells (70% increase of CD11b) was attenuated by coincubation of the PMN with 0.5 and 5 microM ketamine (47% and 44% increase, respectively). CONCLUSION: These data suggest that ketamine exerts its antiinflammatory actions primarily via inhibition of leukocyte reactivity. Indeed, no inhibition of endothelial responses was detectable in our study.

Anesthetics, Dissociative↗
PubMed1999

S(+)-ketamine, but not R(-)-ketamine, reduces postischemic adherence of neutrophils in the coronary system of isolated guinea pig hearts.

UNLABELLED: Polymorphonuclear neutrophils (PMN) play a crucial role in the initiation of reperfusion injury. In a previous study, we found that ketamine reduced the postischemic adherence of PMN to the intact coronary system of isolated guinea pig hearts. Because ketamine is a racemic mixture (1:1) of two optical enantiomers, we looked for possible differences in action between the stereoisomers. Seventy-six guinea pig hearts were perfused in the "Langendorff" mode under conditions of constant flow (5 mL/min) using modified Krebs-Henseleit buffer. After 15 min of global warm ischemia, freshly isolated human PMN (10(6)) were infused as a bolus into the coronary system during the second minute of reperfusion. PMN adhesion was expressed as the numeric difference between PMN recovered in the effluent and those applied. Series A hearts received 5 microM S(+), 5 microM R(-), or 10 microM racemic ketamine starting 20 min before ischemia and during reperfusion. In Series B hearts, 10 microM nitro-L-arginine, an inhibitor of NO synthase, was added to the perfusate. In Series C, PMN were preincubated for 15 min with 5 microM S(+)- or R(-)-ketamine. Coronary vascular leak was assessed by measuring the rate of formation of transudate on the epicardial surface. Ischemia/reperfusion without anesthetics increased coronary PMN adherence from 25.5% +/-2.3% (basal) to 35.3%+/-1.5% of the number applied. S(+)-ketamine reduced postischemic adherence in each series (A, 25.5%+/-5.1%; B, 22.5%+/-1.7%; C, 25.3%+/-7.7%), as did racemate (A, 26.4%+/-3.7%). Although 5 microM R(-)-ketamine had no effect on adhesion (A, 30.5%+/-6.7%; B, 34.3%+/-5.1%; C, 34.3%+/-4.3%), it significantly increased vascular leak in the presence of NOLAG. These findings indicate stereoselective differences in biological action between the two ketamine isomers: S(+)-ketamine inhibited PMN adherence, R(-)-ketamine worsened coronary vascular leak in reperfused isolated hearts. IMPLICATIONS: In this study, we demonstrated stereoselective differences in the biologic action of the two ketamine isomers in an animal model of myocardial ischemia. Polymorphonuclear neutrophil adherence to the coronary vasculature after ischemia was inhibited by S(+)-ketamine, whereas R(-)-ketamine increased coronary vascular fluid leak.

Anesthetics, Dissociative↗
PubMed1999

Inhibition of neutrophil activation by volatile anesthetics decreases adhesion to cultured human endothelial cells.

BACKGROUND: Polymorphonuclear leukocytes (neutrophils, PMNs) have been shown to mediate vascular and tissue injury, leading to so-called systemic inflammatory response syndrome. The authors evaluated the effect of volatile anesthetics on neutrophil adhesion to human endothelial cells, focusing on whether the inhibitory effect observed is linked to an alteration in the function of endothelial cells or neutrophils. METHODS: The adhesion of human PMNs was quantified using cultured human umbilical vein endothelial cells (HUVECs). The increase in the number of adhering PMNs was assessed when HUVECs (with 1 mM hydrogen peroxide), PMNs (with 10 nM N-formyl-methionyl-leucyl-phenylalanine), or both were prestimulated. To determine the influence of volatile anesthetics on the adhesion of PMNs, the experiments were performed in the absence or presence of 0.5, 1, and 2 minimum alveolar concentration halothane, isoflurane, or sevoflurane, whereby HUVECs, PMNs, or both were pretreated with gas. RESULTS: Activation of HUVECs with hydrogen peroxide or stimulation of PMNs with N-formyl-methionyl-leucyl-phenylalanine resulted in a 2.5-fold increase in PMN adhesion. Preincubation of PMNs, separately, with halothane, isoflurane, or sevoflurane, respectively, abolished enhanced neutrophil adhesion to hydrogen peroxide-activated HUVECs and adhesion of PMNs prestimulated with N-formyl-methionyl-leucyl-phenylalanine to unstimulated HUVECs (maximal effect at 1 minimum alveolar concentration). No decrease in adhesion was detected when only HUVECs were pretreated with volatile anesthetics. Additional exposure of HUVECs and PMNs to volatile anesthetics had no inhibitory effect on adhesion greater than that seen when only PMNs were treated. Appropriately, the volatile anesthetics abolished the upward regulation of the adhesion molecule CD11b on PMNs (as evaluated at 1 minimum alveolar concentration each), whereas 1 minimum alveolar concentration halothane failed to affect the expression of P-selectin, an adhesion molecule on endothelial cells. CONCLUSIONS: This study indicates that halothane, isoflurane, and sevoflurane inhibit neutrophil adhesion to human endothelial cells at concentrations relevant to anesthesia in a static system. The effects appear to be mediated by inhibition of PMN activation; that is, by attenuating the upward regulation of neutrophil CD11b.

Anesthetics, Inhalation↗
PubMed1999

Sevoflurane and isoflurane protect the reperfused guinea pig heart by reducing postischemic adhesion of polymorphonuclear neutrophils.

BACKGROUND: Polymorphonuclear neutrophils (PMNs) contribute to reperfusion injury. Because volatile anesthetics can reduce PMN adhesion in the reperfused, nonworking heart, the authors analyzed whether this action of volatile anesthetics affects cardiac performance after ischemia and reperfusion and further clarified the underlying mechanism. METHODS: Isolated guinea pig hearts perfused with crystalloid buffer and performing pressure-volume work were used. Hearts were subjected to 15 min global ischemia and 20 min reperfusion. In the intervention groups an intracoronary bolus of 3 x 10(6) PMNs was applied in the second min of reperfusion, either in the absence or presence of 0.5 or 1 minimum alveolar concentration sevoflurane or isoflurane. The number of sequestered PMNs was calculated from the difference between coronary input and output (coronary effluent) of PMNs. Performance of external heart work, determined pre- and postischemically, served as criterion for recovery of myocardial function. Additionally, the expression of the integrin CD11b on the cell surface of PMN was measured before and after coronary passage. RESULTS: Injection of PMN in the reperfusion phase, but not under nonischemic conditions, reduced recovery of external heart work significantly (from 55+/-7% to 19+/-11%). Addition of sevoflurane or isoflurane in concentrations of 0.5 and 1 minimum alveolar concentration to the perfusate reduced postischemic PMN adhesion from 36+/-8% to basal values (20+/-7%) and prevented decline of cardiac function. CD11b expression on PMNs increased significantly during postischemic coronary passage under control conditions. Again, both anesthetics in both concentrations inhibited that activation. CONCLUSIONS: Volatile anesthetics reduce PMN adhesion in the reperfused coronary system and thereby preserve cardiac function. Reduced expression of the adhesion molecule CD11b on PMNs in the presence of sevoflurane or isoflurane is, at least in part, responsible for the cardioprotective effect.

Anesthetics, Inhalation↗
PubMed1998

Influence of intact left atrial appendage on hemodynamic parameters of isolated guinea pig heart.

BACKGROUND: In isolated working guinea pig heart preparations using the conventional technique of cannulating the left atrium via the atrial appendage, the resulting cardiac output is often insufficiently low (15-20 ml/min). This is a problem in ischemia reperfusion studies where small absolute differences can be responsible for large relative changes comparing pre- and postischemic values. In an attempt to increase cardiac output, the left atrium was left intact in isolated working guinea pig hearts. The two techniques were compared for hemodynamic parameters and their similarity to the physiological condition. METHODS: The left atrium was cannulated either via the orifices of the pulmonary veins or via an incision in the atrial appendage with its subsequent ligation around the cannula (n = 45-46/group). After 20 min of pressure-volume work cardiac output, heart rate and oxygen partial pressures were measured and myocardial oxygen consumption and cardiac efficiency were calculated. RESULTS: Cardiac output was higher in hearts with intact atrial appendage (64 +/- 2 ml/min) than in hearts with ligated atrial appendage (33 +/- 1 ml/min). Myocardial oxygen consumption (6.1 +/- 0.2 and 8.4 +/- 0.3 micromol/min, resp.) and cardiac efficiency (12.8 +/- 0.6% and 19.9 +/- 0.8%, resp.) were significantly higher in hearts with intact left atrial appendage. CONCLUSIONS: Isolated working guinea pig hearts with an intact left auricle exhibit higher values for important hemodynamic parameters compared to a preparation technique involving ligation of the left auricle.

Animals↗
PubMed1998

Disparate effects of adhesion and degranulation of platelets on myocardial and coronary function in postischaemic hearts.

OBJECTIVE: Beside the major effect of acute thrombus formation, little is known about the interaction of platelets with the coronary endothelium in an ischaemia-reperfusion situation. The present study was designed to investigate, separately, the consequences of platelet adhesion and degranulation during myocardial reperfusion. METHODS: Isolated guinea pig hearts perfused with Krebs-Henseleit buffer and performing pressure-volume work were used. We infringed myocardial function by imposing ischaemia (20 min of low-flow perfusion with 1 ml/min and 10 min of global ischaemia) and reperfusion (15 min with 5 ml/min). During low-flow perfusion, the coronary endothelium was stimulated by thrombin before and during infusion of a bolus: 10(8) washed human platelets +/- the Arg-Gly-Asp (RGD) analogon lamifiban, the supernatant of 10(8) thrombin-stimulated platelets, fibrinogen (2 microM), lamifiban (2 microM) or Tyrode's solution (control group). The parameter external heart work (EHW), determined pre- and postischaemically, served as criterion for recovery of myocardial function. Additionally, the formation of capillary transudate was measured during the reperfusion phase to assess coronary permeability. Coronary perfusion pressure was monitored continuously and myocardial production of lactate and consumption of pyruvate were measured. Electron microscopy of hearts was performed after platelet application to verify platelet adhesion in the coronary system. RESULTS: Recovery of EHW by hearts without platelet application was 64 +/- 3% and was significantly reduced to 49 +/- 5% by platelet infusion (n = 8 each). Infusion of supernatant of thrombin-stimulated platelets did not impair recovery of heart work. In the reperfusion phase (6th-10th min), hearts that either had received platelets or supernatant of platelets exhibited a significantly reduced production of capillary transudate (70 microliters/min vs. 180 microliters/min for the controls). Intracoronary bolus application of fibrinogen or lamifiban also reduced coronary leak. Coronary perfusion pressure and metabolic parameters were not statistically different between the groups at any time. CONCLUSIONS: Platelet adhesion to the coronary endothelium in a situation of myocardial ischaemia impairs cardiac recovery, whereas constituents released by platelets may have beneficial effects on the integrity of the coronary endothelium. In particular, fibrinogen seems to contribute to the permeability reducing effect, possibly by interaction with endothelial receptors recognising the RGD sequence.

Acetates↗
PubMed1998

Adenosine endogenously released during early reperfusion mitigates postischemic myocardial dysfunction by inhibiting platelet adhesion.

The purpose of this study was to investigate platelet effects on postischemic heart function in conjunction with adenosine effects on intracoronary platelet adhesion. Homologous platelets were infused into the coronaries of isolated guinea pig hearts, either during low-flow ischemia or during reperfusion, and external heart work (EHW) and intracoronary platelet adhesion were determined. In most experiments, thrombin was added to the perfusate. The influence of endogenous adenosine was studied by use of the uptake blocker dipyridamole and the unspecific adenosine-receptor blocker theophylline, the A1-receptor blocker 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), and the A2-receptor blocker 3,7-dimethyl-1-propargylxanthine (DMPX). The importance of nitric oxide and prostaglandin I2 (PGI2) was tested by using nitro-L-arginine (NOLAG) and indomethacin, respectively. When platelets were applied with thrombin during low-flow ischemia, EHW recovered to only 63 +/- 4% of the preischemic value, as compared with 89 +/- 3% without platelets (p < 0.05). Despite thrombin, platelets incurred no significant functional loss when applied in the first minute of reperfusion (but again in the fifth minute); however, when theophylline was also present, recovery of EHW amounted to only 42 +/- 12%. Intracoronary adhesion of platelets was negligible without thrombin, and highest during low-flow ischemia with thrombin (35 +/- 3% of the applied number). No adhesion occurred during the first minute of reperfusion, whereas in the fifth minute, adhesion was again 20.8 +/- 4%. Dipyridamole increased adenosine release and attenuated adhesion at this time. Theophylline increased adhesion in the first minute of reperfusion (33 +/- 6.4%), whereas NOLAG and indomethacin proved to be ineffective. DPCPX and DMPX each increased platelet retention during the first minute of reperfusion, their effects being additive. Intracoronary adhesion of platelets induced by thrombin in isolated hearts can reduce postischemic recovery of heart function. During reperfusion, but not during low-flow, endogenous adenosine can prevent platelet adhesion and loss of myocardial function, an action mediated both by A1- and A2-receptor-dependent mechanisms.

Adenosine↗
PubMed1998

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts.

BACKGROUND: Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far. METHODS: Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined. RESULTS: At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1 +/- 1.2% (mean +/- SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2 +/- 1.2%), sevoflurane (to 4.4 +/- 0.9%) or halothane (to 3.2 +/- 1.5%) (each P < 0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics. CONCLUSION: Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.

Anesthetics, Inhalation↗
PubMed1997

The function of neutrophils isolated by a magnetic antibody cell separation technique is not altered in comparison to a density gradient centrifugation method.

Most comparative studies on neutrophil (PMN) isolation techniques have shown either activation or functional impairment of the cells due to the different separation processes. We have established a preparation method for PMN from human whole blood employing iron tagged, magnetizable antibodies against the cell surface antigen CD15. The aim of our study was to test whether this magnetic separation (MACS) alters cellular functions of PMN in comparison to a conventional density gradient technique (Percoll). The purity, cell yield, and pre-activation of the cells were evaluated. The latter was assessed by quantifying the expression of the integrin CD11b using flow cytometry. Furthermore, as functional tests, cell morphology and the oxidative burst reaction were investigated. We have shown that the use of 'magnetic' antibodies leads to highly purified PMN (> 99% of isolated leukocytes), while there is still contamination by eosinophils (about 6%) after Percoll separation. Platelet contamination was about the same in both procedures (approx. one platelet per two PMN). The basal expression of CD11b and, hence, neutrophil activation, was significantly lower and the upregulation of CD11b in response to FMLP was more pronounced after magnetic separation, as compared to density gradient centrifugation. The MACS technique did not lead to polarisation of PMN, nor did it affect the oxidative burst. This study suggests that magnetic separation is a simple, time-saving technique, yielding highly purified and functionally intact PMN.

Centrifugation, Density Gradient↗
PubMed1997

Cardioprotection by cyclosporine A in experimental ischemia and reperfusion--evidence for a nitric oxide-dependent mechanism mediated by endothelin.

The acute effect of cyclosporine A (CSA) on myocardial function after ischemia and reperfusion and the mechanism of action was investigated in isolated working guinea-pig hearts. Myocardial function was experimentally infringed by imposing short-term global ischemia and reperfusion (15 min each). External heart work (EHW), determined before and after ischemia, served as the criterion for quantitation of recovery. Control hearts were perfused with modified Krebs-Henseleit buffer, other hearts received buffer supplemented with CsA +/- an endothelin receptor antagonist or exogenous endothelin +/- an inhibitor of nitric oxide (NO) synthesis. To assess the importance of endothelial production of mediators directly, NO release in coronary effluent (continuously measured with an amperometric sensor) and release of 6-keto-prostaglandin F1, (6-keto-PGFb), a stable metabolite of prostacyclin (PGI2), were determined in non-working. Langendorff hearts. Oxidative stress during reperfusion was assessed by measuring glutathione release in coronary venous effluent. Cyclosporine A (0.8 microM) improved post-ischemic function significantly (59% recovery of EHW nu 31% for controls). At 0.08 microM. CsA was without beneficial effect (30% recovery). The endothelin (ET)A- and ETB-receptor antagonist bosentan inhibited the protective action of 0.8 microM CsA (32% recovery). Exogenous ET-1 (80 pM) improved recovery to 53%, an effect which was blocked by the inhibitor of NO-synthase, NG-nitro-L-arginine (NOLAG. 1 microM. 31% recovery. In the control group, post-ischemic NO release in coronary effluent recovered from zero to about 100% of the pre-ischemic value by 10 min. but then decreased rapidly during the subsequent 15 min of reperfusion. In hearts treated with 0.8 microM CsA, NO release stayed at 100% of the pre-ischemic value throughout reperfusion, the difference between controls and CsA-treated hearts being significant after 20 min of reperfusion. On the other hand, coronary venous release of 6-keto-PGF1a was not different between the groups. Release of glutathione during early reperfusion first 5 min) was significantly lowered (P < 0.05) to about 50% in CsA (0.8 microMI- and ET-I-treated compared with controls (8.8 nmol/min). Cyclosporine A acts as a cardioprotective agent in our model of ischemia and reperfusion, presumably by elevating the level of endogenous nitric oxide and thereby reducing oxidative stress.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Effects of ACE-inhibition on redox status and expression of P-selectin of endothelial cells subjected to oxidative stress.

Redox stress during post-ischemic reperfusion may be the prime signal for processes leading to myocardial remodelling and hypertrophy. Nitric oxide (NO) is antioxidative, antiadhesive for neutrophils (PMN) and antiproliferative. Thus, enhancing endothelial production of NO, e.g. by inhibiting breakdown of endogenous bradykinin via angiotensin converting enzyme (ACE), could be beneficial. The effect of cilazaprilat (CILA, 10 micro M), an ACE inhibitor, on redox status, expression of the adhesion molecule P-selectin, and PMN adhesion under conditions of oxidative stress was investigated in cultured human umbilical vein endothelial cells (HUVECs). Incubation of the cells with H2O2 (0.1 and 1 mm) for 15 min served as oxidative stimulus. The intra- and extracellular concentrations of reduced and oxidized glutathione (GSH and GSSG) were measured by HPLC as indicators of endothelial redox status. Expression of P-selectin was measured by flow cytometry. Furthermore, firm leukocyte adhesion to HUVECs was assessed. In controls, the intracellular ratio GSH/GSSG averaged 47 and dropped to 30 after incubation with 0.1 mm H2O2. The ratio declined to 6.5 with 1 mm H2O2. CILA blocked the effects of 0.1 mm H2O2, but was ineffective against 1 mm peroxide. The extracellular ratio did not discriminate between 0.1 and 1 mm H2O2, falling from 18 to 1 in both situations. P-selectin expression rose from 100% (control) to 146% after 1 mm H2O2 without CILA, but only to 114% in the presence of CILA. PMN adhesion was enhanced from about 1600 PMN per microwell (control) to 4300/well by 1 mm H2O2. CILA had no significant effect on adhesion (3900 PMN/well). Exposure of HUVECs to 0.1 mm H2O2 affected neither P-selectin expression nor PMN adhesion. Consequently, ACE inhibition can mitigate mild (0.1 mm H2O2) but not more severe redox stress in HUVECs. Irrespectively, CILA reduced the upregulation of P-selectin at the higher H2O2 concentration, indicating that this process is regulated independently of the cellular redox status. The firm adhesion of PMN to HUVECs was independent of P-selectin expression.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Retention of leucocytes in reperfused, isolated hearts does not cause haemodynamically relevant permanent capillary plugging.

Effects of microspheres (5 microns or 10 microns diameter) and polymorphonuclear leucocytes (PMN) on coronary resistance were compared in beating, non-working isolated guinea-pig hearts (Langendorff preparation). The hearts were buffer perfused (5 ml/min, constant flow) and particles or cells were infused into the coronary system as a bolus (1 ml, 1 min). Coronary perfusion pressure, coronary flow and formation of epicardial transudate were measured before and after bolus administration. Coronary resistance was estimated from these parameters. Retention of particles or cells was monitored by quantifying the numbers emerging in the coronary effluent in relation to the number administered. The effects of PMN were also studied after 15 min of global ischemia. Coronary resistance correlated with the number of 10-micron particles infused, which were almost quantitatively retained. In contrast, 5-micron beads had no such effect and were not retained in the coronary system. Though considerable numbers of PMN were retained in the hearts (about 21% under control conditions and 35% after ischaemia), coronary resistance was not increased in either case. Blockage of the CD18 adhesion complex by monoclonal antibodies lowered basal retention to 11% and completely prevented the elevation of retention by ischaemia. We conclude that, in this experimental model, PMN, permanently retained in the hearts under normal flow conditions and especially after brief ischaemia, do not cause acute, haemodynamically relevant capillary plugging, but adhere to postcapillary venules via CD18.

Animals↗
PubMed1997

ACE-inhibition prevents postischemic coronary leukocyte adhesion and leukocyte-dependent reperfusion injury.

OBJECTIVE: Polymorphonuclear leukocytes (PMN), retained in the microvascular bed, can contribute to postischemic myocardial reperfusion injury. Since a beneficial effect of ACE-inhibition on reperfusion injury has been reported, we investigated the impact of cilazaprilat on PMN dependent reperfusion injury in isolated guinea pig hearts. METHODS: Hearts (n = 5 per group) were subjected to 15 min of ischemia. Immediately thereafter, a bolus of PMN was injected into the coronary system. External heart work (EHW) and total cardiac nitric oxide release were measured. For microscopic evaluation, hearts received rhodamine 6G labelled PMN after ischemia, were arrested 5 min later and further perfused with FITC dextran (0.1%). Localization of retained PMN was assessed by fluorescence microscopy. Leukocyte activation was studied by FACS analysis of the adhesion molecule CD11b before and after coronary passage of the PMN. The ACE-inhibitor cilazaprilat (Cila, 2 microM) and the NO-synthase inhibitor nitro-L-arginine (NOLAG, 10 microM) were used to modulate nitric oxide formation of the heart. RESULTS: Postischemic EHW recovered to 67 +/- 5% (controls) and 64 +/- 6% (Cila) of the preischemic value. Addition of PMN severely depressed recovery of EHW (39 +/- 2%) and NO release (39 +/- 6% of the preischemic value). Simultaneously, ischemia led to a substantial increase in postcapillary PMN adhesion (from 21 +/- 5 to 172 +/- 27 PMN/mm2 surface) and CD11b-expression of the recovered PMN (3-fold). Cila attenuated postischemic PMN adhesion (83 +/- 52 PMN/mm2) and activation of PMN, whereas it improved recovery of work performance (64 +/- 4%) and NO release (65 +/- 4%) in the presence of PMN. Conversely, NOLAG increased PMN adhesion (284 +/- 40 PMN/mm2) and myocardial injury. We conclude that ACE-inhibition prevents leukocyte dependent reperfusion injury mainly by inhibition of postcapillary leukocyte adhesion. The effect may be mediated by NO, given the proadhesive effect of NOLAG.

Analysis of Variance↗
PubMed1997

Halothane, isoflurane, and sevoflurane reduce postischemic adhesion of neutrophils in the coronary system.

BACKGROUND: Polymorphonuclear neutrophils (PMNs) contribute to postischemic reperfusion damage in many organs and tissues, a prerequisite being adhesion of PMNs to vascular endothelial cells. Because adhesion processes involve orderly interactions of membrane proteins, it appeared possible that "membrane effects" of volatile anesthetics could interfere. We investigated the effects of halothane, isoflurane, and sevoflurane on postischemic adhesion of human PMNs in the intact coronary system of isolated perfused guinea pig hearts. METHODS: The hearts (n = 7-10 per group) were perfused in the "Langendorff" mode under conditions of constant flow (5 ml/min) using modified Krebs-Henseleit buffer equilibrated with 94.4% oxygen and 5.6% carbon dioxide. Global myocardial ischemia was induced by interrupting perfusion for 15 min. In the second minute of reperfusion (5 ml/min), a bolus dose of 6 x 10(5) PMNs was injected into the coronary system. The number of cells reemerging in the coronary effluent was expressed as a percentage of the total number of applied PMNs. Halothane, isoflurane, and sevoflurane, each at 1 and 2 minimal alveolar concentration (MAC), were vaporized in the gas mixture and applied from 14 min before ischemia until the end of the experiment. RESULTS: Under nonischemic conditions, 24.7 +/- 1.3% of the injected neutrophils did not reemerge from the perfused coronary system. Subjecting the hearts to global ischemia augmented retention (36.4 +/- 2.8%, P < .05). Application of halothane reduced adhesion of neutrophils to 22.6 +/- 2.1% and 24.2 +/- 1.8% at 1 and 2 MAC, respectively (P < .05). Exposure to 1 and 2 MAC isoflurane was similarly effective, whereas basal adhesion was not significantly influenced. Sevoflurane-treated hearts (1 and 2 MAC) also showed decreased adhesion of PMNs (23 +/- 2.3% and 24.8 +/- 1.8%, respectively; P < .05) and an identical reduction resulted when sevoflurane (1 MAC) was applied only with the onset of reperfusion. CONCLUSIONS: Although the mechanism of action of volatile anesthetics remains unclear in these preliminary studies, their inhibitory effect on ischemia-induced adhesion of PMNs may be beneficial for the heart during general anesthesia.

Anesthetics, Inhalation↗
PubMed1997

Hemodynamic effects of isoprostanes (8-iso-prostaglandin F2alpha and E2) in isolated guinea pig hearts.

Isoprostanes are a family of prostaglandin-related compounds formed from arachidonic acid in a cyclooxygenase-independent manner as products of free radical-initiated lipid peroxidation. To elucidate the biological activity of the F2-and E2-isoprostanes, 8-iso-prostaglandin F2alpha (8-iso-PGF2alpha) and 8-iso-prostaglandin E2 (8-iso-PGE2), we measured hemodynamic effects in isolated perfused guinea pig hearts after cumulative administration (3 x 10(-9)-10(-5) M) of these compounds into the coronary system. Coronary flow (CF), left ventricular pressure (LVP), maximal rate of pressure development (dP/dt(max)), and heart rate were determined continuously. Furthermore, net release of lactate into the coronary venous effluent and myocardial pyruvate consumption were measured. Comparative studies were performed with the known potent vasoconstrictor endothelin-1 (6 x 10(-12)-2 x 10(-9) M). Both 8-iso-PGF2alpha and 8-iso-PGE2 induced concentration-dependent decreases in CF, which declined maximally to approximately 50% of the baseline level. The potencies of the two compounds were almost identical. Alterations in CF were associated in both groups with parallel reductions of LVP and dP/dt(max); heart rate was not influenced. Furthermore, the diminished CF caused enhanced lactate release and a reduced pyruvate consumption. All isoprostane-induced hemodynamic changes were prevented by coapplication of the thromboxane A2-receptor antagonist SQ 29548 (1 microM). Endothelin-1 caused CF reductions associated with loss of myocardial contractility, just like the isoprostanes. We conclude that in isolated guinea pig hearts, 8-iso-PGF2alpha and 8-iso-PGE2 are potent vasoconstrictors. The action appears to be mediated by SQ 29548-responsive thromboxane receptors. The accompanying loss of contractility is a secondary phenomenon, elicited by infringed oxygen supply.

Animals↗