[Effect of arginine-dependent nitric oxide synthesis on regional perfusion of the eye in the anesthesized dog].

The changes of the retinal and uveal perfusion after inhibition of the arginine-dependent nitric oxide (NO) synthesis by systemic administration of NG-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg bw i.v.) were studied in four anesthetized dogs using the tracer microsphere technique. The regional perfusion rates (ml.min-1.g-1) under steady-state control conditions were: retina 0.13 +/- 0.05, choroid 8.26 +/- 1.85, iris 0.24 +/- 0.05 and ciliary body 1.11 +/- 0.26. Infusion of L-NAME over 10 min reduced the perfusion of the retina on the average by 23% (P > 0.05). The perfusion of choroid, iris and ciliary body fell by 54 +/- 8%, 58 +/- 7% and 53 +/- 8%, respectively (P < or = 0.05 for all). In five additional experiments the local activity of NO-producing enzymes (NO synthases) was determined by measuring the production rate of citrullin in tissue extracts of the different eye regions. Total NO synthase activities (pmol citrullin.min-1.g-1) were: retina 31.0 +/- 5.5, choroid 3.1 +/- 2.8, iris 7.1 +/- 2.1 and ciliary body 1.3 +/- 1.3. Differences of the total NO synthase activities of retina, iris and cilary body were statistically significant (P < or = 0.02). The results show that the uvea perfusion is largely influenced by the steady-state production of NO. The homogeneous flow reduction in the uvea after inhibition of NO synthase is contrasted by the heterogeneous NO synthase activities of the different uvea regions.(ABSTRACT TRUNCATED AT 250 WORDS)