Attenuated nitric oxide synthase activity and protein expression accompanyintestinal ischemia/reperfusion injury in rats

intestinal ischemia/reperfusion (I/R) leads to bowel impairment via the rel ease of reactive oxygen species (ROS) and neutrophil infiltration. in addit ion to modulating intestinal integrity, nitric oxide (NO.) inhibits neutrop hil activation and scavenges ROS. Attenuated endogenous NO. formation may r esult in the accrual of these deleterious stimuli. Therefore, we determined nitric oxide synthase (NOS) activity in anesthetized rats subjected to 1 h of superior mesenteric ischemia or ischemia followed by reflow. NOS activi ty was measured in intestinal tissue homogenates as the conversion rate of H-3-L-arginine to H-3-L-citrulline. Our results demonstrate that intestinal ischemia leads to a decrease in NOS activity indicating lower NO. formatio n in the animal model. The attenuation in NOS activity was not reversed fol lowing 4 h of reperfusion. Western blot analysis revealed that the decline in enzyme activity was accompanied by reduced intestinal NOS HI (endothelia l constitutive NOS) expression. These findings provide biochemical evidence for impaired NO. formation machinery in intestinal YR injury. (C) 2000 Aca demic Press.