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Nitric oxide production by isolated human and porcine ciliary processes
T Haufschild1, M R Tschudi, J Flammer
1Laboratory of Ocular Pharmacology and Physiology, University Eye Clinic, Basel, Switzerland.
Background:
In the kidney, the trachea, and the colon, nitric oxide (NO) can modulate transepithelial fluid transport. This study investigates whether isolated human and porcine ciliary processes produce NO.
Methods:
Porcine ciliary processes and iris were used either fresh or thawed after storage at -70 degrees C. Post-mortem (8-12 h) human ciliary processes were used thawed after storage at -70 degrees C. NO was measured by placing a nafion-coated polymeric porphyrinic microsensor (differential pulse voltammetry) on the surface of the tissue. Measurements were conducted in the absence or in the presence of the NO formation inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME; 0.2 mM, 1 mM) or its biologically inactive D-enantiomer N(G)-nitro-D-arginine methyl ester (D-NAME; 1 mM).
Results:
NO concentrations in porcine ciliary processes (1.27+/-0.25 microM) were higher (P=0.001) than those in the iris (0.00+/-0.02 microM) and were significantly (P<0.001) decreased by L-NAME (fresh specimen). From thawed porcine ciliary processes, NO concentrations measured (1.85+/-0.47 microM) were not significantly different (P=0.16) from those measured in fresh specimen and were also reduced (P <0.001) by L-NAME, but not by D-NAME. In human ciliary processes, NO concentrations measured (0.08+/-0.11 microM) were somehow lower but were again decreased (P<0.001) by L-NAME (thawed specimen).
Conclusion:
Reflecting the biological activity of a nitric oxide synthase, isolated human and porcine ciliary processes produce NO.