Nitric oxide (NO) is believed to play an important role in sepsis-related hypotension. We examined the effects of two pore-forming bacterial exotoxins, Escherichia coli hemolysin and Staphylococcus aureus alpha-toxin, on NO formation in cultured porcine pulmonary artery endothelial cells. NO was quantified using a difference-spectrophotometric method based on the rapid and stoichiometric reaction of NO with oxyhemoglobin. Endothelial cyclic guanosine monophosphate levels were also monitored. Both exotoxins increased NO synthesis in endothelial cells in a time- and dose-dependent manner to an extent exceeding that observed with the ionophore A23187 or thrombin. The capacity of exotoxins to induce NO formation may be relevant in patients with severe local or systemic bacterial infections.

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