Exhaled nitric oxide in endotoxin-treated rats: isolated perfused lung versus intact animal

Isolated perfused lung preparation (IPL) is a commonly used method to study pulmonary vascular resistance and reactivity in endotoxin-treated rats. While in intact rats endotoxin increases exhaled nitric oxide (eNO),1 less is known about eNO production in IPL. In the present study we measured eNO in 5 IPL and 5 anesthetized male Spr ague -Daw ley rats 3h after i.p. injection of endotoxin (E. coll lipopolysaccharide; 20 mg/kg). Samples of expired gas were collected every 15min for 105min and the concentration of eNO was immediately measured by using chemiluminescence (Siever 270B) . In intact rats eNO did not change significantly during the period of the measurement < 92 . 8±15.5 ppb £mean±SE] at Omin and 115. 0±32 . 4 at lOSmin; AHOVA) . in IPL, the Omin level of eNO (42. 3±8.9) was lower compared to the intact animals (P<0.05; t-teot). Furthermore, it decreased over time and became significantly lower at 45min and reached a level of 25.8±5.5 at 105min <P<0.05) . The addition of L-arginine (1.4mM) to IPL at 105min was associated with a significant increase in eNO at 135min and it reached 105.4±34.4 at 210min (P<0.05). He conclude that marked reduction in eNO occurs in IPL from endotoxin-treated rats which is most likely due to a rapid depletion in L-arginine. This effect should be considered when IPL is used as a means to study NO production in endotoxic shock models. 1] Am J Respir Crit Care Med 1995;151:713-8.