Figure 3. Treatment with the NOS2-selective inhibitor aminoguanidine improves responsiveness to inhaled NO in lungs of LPS-treated rats. Rats were treated with LPS (n = 7) or remained untreated control rats (n = 5). After 4 h, rats received a bolus injection of aminoguanidine (30 mg/kg), and 12 h later, the lungs were isolated, perfused, and ventilated. The PAP was elevated using U46691, and the vasodilator response to ventilation with 0.4, 4, and 40 ppm NO was measured. Compared to lungs from LPS-treated rats without aminoguanidine (n = 6), there was an improved response to inhaled NO in lungs from rats treated with LPS and aminoguanidine (*P < 0.05 LPS with aminoguanidine differs from LPS alone at each level of NO).