Nitric oxide production by isolated human and porcine ciliary processes.

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.