Bolus application of endotoxin to healthy volunteers results in reversible hemodynamic alterations, such as observed in septic cardiomyopathy. Currently, endotoxin-induced cardiodepression is mainly attributed to the endotoxin-induced release of proinflammatory cytokines into the circulation, particularly of tumor necrosis factor alpha and interleukin-1, the serum levels of these cytokines being enhanced in sepsis and septic shock, and also in various heart diseases. In this study, we report a proinflammatory effect of endotoxin (1-10 micrograms/ml, 24-h incubation period) on neonatal rat cardiomyocytes in serum-free culture, evidenced by induction of inducible nitric oxide synthase, enhanced release of nitrite (protein synthesis-dependent) and interleukin-6 into the supernatant, as well as an increase in cell-associated interleukin-1 and a specific cardiodepressant profile: endotoxin disrupts beta-adrenoceptor-mediated increase in pulsation amplitude, but alpha-adrenoceptor-induced increase in pulsation amplitude and arrhythmias are not suppressed. In the presence of dexamethasone (0.1 microM), the endotoxin-mediated blockade of beta-adrenergic responsiveness, as well as induction of inducible nitric oxide synthase, enhanced nitrite release and interleukin-1/-6-production are inhibited. In contrast, tumor necrosis factor alpha at a low concentration (10 U/ml) depresses alpha- and beta-adrenergic responsiveness in the presence of dexamethasone in a nitric oxide-independent manner. These data suggest a stimulatory effect of endotoxin on the cardiomyocyte and a specific proinflammatory and nitric oxide-dependent cardiodepressant profile of endotoxin.