Vol. 297, Issue 1, 128-132, April 2001

Intravasal Peroxynitrite Generation Causes Dysfunction in the Isolated Perfused Rat Lung via Endothelin

Katja Eichert, Jürg Hamacher, Michael Andreas Wunder and Albrecht Wendel

Biochemical Pharmacology, Department of Biology, University of Konstanz, Konstanz, Germany

In septic shock excessive nitric oxide and superoxide are produced, thus generating peroxynitrite. This study investigates whether and how intravasal peroxynitrite causes lung dysfunction. To generate peroxynitrite, isolated and ventilated rat lungs were perfused blood-free in a pressure-constant, recirculating mode with hypoxanthine/xanthine oxidase plus sodium nitroprusside. Airway and vascular resistance, and release of thromboxane A₂, prostacyclin, and endothelin-1 were assessed over 200 min. Peroxynitrite generation, as demonstrated by oxidation of the marker 2',7'-dichlorodihydrofluorescein diacetate, caused broncho- and vasoconstriction starting after 100 min. Both reactants alone, i.e., NO^· or O₂, had no effect. The thromboxane A₂/prostaglandin H₂ receptor antagonist BM13.177 did not affect peroxynitrite-induced broncho- and vasoconstriction. Combined endothelin_A/B (ET_A/B) receptor antagonism (BQ123 plus BQ788) prevented broncho- and vasoconstriction more effectively than the ET_A receptor antagonist BQ123 alone. In tissue from lungs exposed to peroxynitrite, significantly increased amounts of endothelin-1 were detected. This study identifies endothelin-1 rather than prostanoids as a distal mediator induced by the reaction product of superoxide and nitric oxide, i.e., peroxynitrite. It is concluded that 1) endothelin-1 is a causal mediator of peroxynitrite-induced acute rat lung injury, and 2) peroxynitrite-induced broncho- and vasoconstriction are mediated by both ET_A and ET_B receptors.