NG-nitro-L-arginine methylester, a nitric oxide synthase inhibitor, diminishes apoptosis induced by ischemia-reperfusion in the rat bladder

Aims. To evaluated the effects of N-G-nitro-L-arginine methylester (L-NAME), a nitric oxide synthase (NOS) inhibitor, on apoptosis induced by ischemia-reperfusion injury in the rat through a muscle bath and TUNEL staining. Methods. The rat abdominal aorta was clamped to induce ischemia-reperfusion (I-R) injury in the rat bladder dome with or without L-NAME (30 mg/kg, i.p. 30 minutes before the ischemia) according to our previous reports [Saito et al., 1998 Life Sci. 62:PL149-56; Saito and Miyagawa, 1999 J. Urol. 162:1490-5]. Some rats were exposed to 30 minutes of ischemia only, whereas others also received 30 minutes, 3 days, or 7 days of reperfusion after the ischemia. Muscle bath studies with carbachol and 100 mM KCl were performed to confirm the bladder function. TUNEL and hematoxylin and eosin staining were performed in the experimental rat bladders to detect apoptosis. Results. The contractile responses of the rat bladder dome after 30 minutes of ischemia differed slightly, not significantly, from those of controls. Reperfusion (30 minutes) produced significant reductions in the contractile responses to carbachol and KCl in the rat bladders. The treatment with L-NAME significantly reduced the extent of reperfusion injury, as judged by pharmacologic experiments. At 3 and 7 days after the induction of ischemia-reperfusion, the contractile responses were improved compared with the 30-minute reperfusion group. For each duration group, treatment with L-NAME significantly increased the contractile responses compared with the I-R group without L-NAME. Ischemia-reperfusion induced apoptosis, and the peak in TUNEL-positive cells was observed 3 days after the insult. Preteatment with L-NAME reduced the induction of apoptosis. Conclusion. Our data indicated treatment with L-NAME can reduce apoptosis induced by ischemia-reperfusion in the bladder.