PHOTOCHEMICAL GENERATION OF NITRIC-OXIDE FROM NITRO-CONTAINING COMPOUNDS - POSSIBLE RELATION TO VASCULAR PHOTORELAXATION PHENOMENA

We examined the production of nitric Oxide (NO) from various nitro-containing compounds (500 muM and 100 muM solutions in Krebs buffer, pH 7.4). Sealed vials containing solutions of NaNO2, N-nitro-L-arginine, 4-nitrophenol, BAY K 8644, or N-nitro-L-arginine methyl ester were stored in the dark, under normal roomlight, or were exposed to ultraviolet light (365 nm), for 30 min (24-degrees-C). NO was measured in the vial headspace after 30 min, using a sensitive assay previously established in our laboratory. Production of NO was found to be dependent on the intensity of light exposure for all compounds, and the highest degree of light-induced production of NO was found for NaNO2 and BAY K 8644 solutions. Since NO is a relaxant of smooth muscle, these results help explain the increased sensitivity to relaxation by UV light of vascular and other types of smooth muscle in the presence of NaNO2, BAY K 8644 and N-nitro-L-arginine, as observed by other investigators.