Myocardial and vascular adrenergic alterations in a rat model of endotoxin shock: reversal by an anti-tumor necrosis factor-alpha monoclonal antibody.

OBJECTIVES: a) To investigate responsiveness to exogenous catecholamines in rat endotoxin shock by studying both myocardial and vascular functional parameters, and to determine the relationship of these parameters with other relevant biological parameters of the adrenergic pathway, such as myocardial beta-adrenergic receptors and cyclic adenosine monophosphate (cAMP); b) to investigate the role of tumor necrosis factor (TNF)-alpha via prophylactic anti-TNF-alpha monoclonal antibody administration. DESIGN: Experimental, comparative hospital. SETTING: Laboratory in a university hospital. SUBJECTS: Male Sprague-Dawley rats, weighing 280 to 340 g. INTERVENTIONS: Intravenous injection of Escherichia coli endotoxin (5 mg/100 g) in the first group; injection of the same dose of endotoxin preceded by 2 mg/100 g of anti-TNF-alpha monoclonal antibody in the second group; injection of saline in the third (control) group. MEASUREMENTS AND MAIN RESULTS: TNF-alpha concentration was measured before and during the first 3 hrs in all three groups. Myocardial and vascular functional parameters were obtained, respectively, from Langendorff perfused hearts and isolated aortic rings. Adrenergic biochemical parameters (catecholamines, density and affinity of beta-receptors, and isoproterenol-stimulated myocardial cAMP) were determined 3 hrs after injections in the three groups. After endotoxin injection, serum TNF-alpha concentrations peaked at 60 mins (2496 +/- 412 pg/mL) and returned slowly to control values at 3 hrs; serum TNF-alpha concentrations remained under the limit of detection in the other two groups. When compared with the control group, plasma concentrations of epinephrine and norepinephrine were significantly (p < .05) increased. Baseline values for differential left ventricular pressure and coronary flow were significantly (p < .001, p < .01, respectively) reduced in the endotoxin group; heart rate remained unchanged. In the endotoxin and control groups, isoproterenol induced a similar increase in differential left ventricular pressure and in heart rate. Anti-TNF-alpha antibody increased cardiac response by partially preventing the decrease by endotoxin in differential left intraventricular pressure. Maximal specific binding of 125iodocyanopindolol and myocardial cAMP accumulation were significantly (p < .01) reduced in the endotoxin group in comparison with the control group. Anti-TNF-alpha antibody prevented the endotoxin-induced decrease in cAMP synthesis (p < .05) but did not modify the density of receptors. Affinity of receptors was similar in the three groups. In aortic rings, endotoxin administration significantly (p < .01) shifted the dose-response curve to norepinephrine to the right, both in the presence and absence of endothelium. NG-monomethyl-L-arginine significantly increased the contractions to attain the control level: p < .001 in the presence of endothelium; p < .05 in the absence of endothelium. Anti-TNF-alpha antibody did not prevent endotoxin-induced vascular hyporeactivity to norepinephrine in either endothelium-intact or -denuded rings, but partially attenuated the decrease in maximal response. CONCLUSIONS: In ex vivo experiments, 3 hrs after endotoxin injection, vascular responsiveness was sharply decreased. This impaired response was improved in vitro by the inhibition of nitric oxide. The heart response to isoproterenol, nevertheless, was maintained, even though there was an obvious decrease in receptor density and an impaired myocardial accumulation of cAMP. Anti-TNF-alpha antibody partially prevented the alteration of both myocardial pressure response to isoproterenol and biochemical parameters, and was not efficacious in preventing vascular hyporeactivity to vasoconstrictor agents.

Alterations of myocardial and vascular adrenergic receptor-mediated responses in Escherichia coli-induced septic shock in the rat.

OBJECTIVES: To investigate responsiveness to exogenous catecholamines in rat bacteremic shock by studying both myocardial and vascular functional parameters; to determine in the same study the relationship of these parameters with other relevant biological parameters of the adrenergic pathway, such as myocardial beta-adrenergic receptors and cyclic adenosine monophosphate (cAMP); and to indirectly approach the roles of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide. DESIGN: Experimental, comparative study. SETTING: Laboratory in a university hospital. SUBJECTS: Male Sprague-Dawley rats, weighing 270 to 320 g. INTERVENTIONS: Intravenous injection of live Escherichia coli DH5 alpha (2 x 10(10) organisms/kg) or saline (0.6 mL) and comparison of the two groups. MEASUREMENTS AND MAIN RESULTS: Mean arterial pressure and heart rate (HR) were recorded, and circulating TNF-alpha concentrations were measured, during the first 3 hrs after E. coli administration. Myocardial and vascular functional parameters were obtained, respectively, from Langendorff-perfused hearts and isolated aortic rings. Adrenergic biochemical parameters (catecholamines, density and affinity of beta-receptors, and isoproterenol-stimulated myocardial cAMP) were determined 3 hrs after E. coli injection. Mean arterial pressure decreased within 5 to 60 mins after bacteria injection and returned to basal levels in the last 2 hrs; HR was unchanged. Serum TNF-alpha concentrations peaked at 120 mins (7333 +/- 672 pg/mL) and were still increased at 3 hrs. Plasma concentrations of epinephrine and norepinephrine were significantly (p < .05) increased. Baseline values for differential left ventricular pressure and coronary flow were significantly (p < .0001, p < .001, respectively) reduced; HR remained unchanged. Isoproterenol induced a similar increase in differential left ventricular pressure and in HR. There was no decrease in the functional myocardial response to adrenergic stimulation. beta-adrenergic receptors were similar in density and in affinity in the two groups. Isoproterenol-stimulated myocardial cAMP was significantly (p < .01) reduced compared with the control group. In aortic rings, bacteria administration significantly (p < .01) shifted the dose-response curve to norepinephrine to the right, both in the presence and absence of endothelium. NG-monomethyl-L-arginine significantly increased the contractions to attain the control level: p < .001 in presence of endothelium; p < .05 in absence of endothelium. CONCLUSIONS: In ex vivo experiments, 3 hrs after E. coli injection, vascular responsiveness was sharply decreased. This impaired response was improved by inhibition of nitric oxide. The heart, nevertheless, was still able to modulate its inotropic and chronotropic response to isoproterenol, even though an impaired beta-adrenergic-receptor stimulation of cAMP was already present.