Direct detection of nitric oxide in rat urinary bladder during ischemia-reperfusion

We attempted to investigate the role of nitric oxide (NO) in ischemia-reperfusion injury in the rat bladder.

Rat abdominal aorta were clamped with a small clip to induce ischemia-reperfusion injury in the rat bladder dome. To investigate the role of NO in ischemia-reperfusion injury, N(G)-nitro-L-arginine methylester (L-NAME, 30 mg./kg.) was injected intraperitoneally to measure carbachol-induced contractions of 60 minutes ischemia-30 minutes reperfusion in the rat bladder dome. In vivo real-time blood flow and NO release were measured in the rat bladder with a laser Doppler flowmeter and an NO-selective electrode, respectively. Moreover, participation of NO synthase subtypes was investigated by immunohistochemical staining of bladder sections with anti-endothelial I and anti-inducible NO synthase subtype antibodies.

Treatment with L-NAME (30 mg./kg., i.p.) partially prevented the reduction of bladder strips in contraction induced by the ischemia-reperfusion. Clamping of the aorta decreased blood flow to 10% of the basal level measured before the clamping. Administration of L-NAME reduced the blood flow to the bladder by 65% compared to the control level during ischemia-reperfusion. Real-time monitoring of NO in the bladder revealed that ischemia increased NO release, which, in turn, reached a plateau 30-40 minutes after the induction of ischemia. Immediately after the reperfusion, NO release returned to the basal level. In the control rat bladder, the endothelial subtype (eNOS) was observed in the mucosa. After the ischemia-reperfusion, iNOS was detected in the infiltrated neutrophils in the muscular and submucosal regions.

Our data indicate that NO from leukocytes may participate in cell/tissue injury during ischemia-reperfusion of the rat bladder and that the damage may be preventable by treatment with L-NAME.