Abstract
We investigated the possibility of there being any photosensitive materials stores yielding nitric oxide (NO), and combined for the first time electrical field stimulation (EFS)- and UV light-induced relaxations in mouse gastric fundus. The tissue responded with relaxation to long wave UV light (366 nm). Repeated exposure to light decreased the fundic photorelaxation in that the initial photorelaxation was 31.5 ± 6.9% whereas the last (10th) photorelaxation was 2.3 ± 0.8%. There were no significant differences between EFS (30 V, 0.5 ms, 1 Hz, 15 s)-induced relaxations obtained before (39.7 ± 7.7%) and after (33.4 ± 9.1%) UV irradiation, which were completely blocked by 10−4 Ml-NG-nitro-arginine methyl ester. Treatment of the tissue with NaNO2,l-NG-nitro-arginine,S-nitrosoglutathione, or sodium nitroprusside for 30 min followed by prolonged washout restored the photorelaxation, whereas glyceryl trinitrate or l-arginine did not produce any improvement. EFS (30 V, 0.5 ms, 3 Hz) applied for 60 min significantly recovered the reduction of the photorelaxation.l-N-δiminoethyl-l-ornithine, which does not contain NO2 moiety, abolished electrically induced relaxation; however, it did not change photorelaxations. UV irradiation caused relaxation only when the adventitial surface of the preparation was oriented to the source of UV light. These results indicate that there could be a photosensitive relaxant materials store yielding NO in the smooth muscle layer of the gastric fundus from mouse. This putative store can be refilled by NaNO2,l-NG-nitro-arginine, sodium nitroprusside, S-nitrosoglutathione, or long-term EFS but not glyceryl trinitrate or l-arginine. Possible candidates for NO-yielding substances might not be an organic nitrate but an intracellular nitrite, nitrosylated substances, and unknown nitro-containing compounds, which could be all sensitive to UV light.
Footnotes
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Send reprint requests to: Dr. Kansu Büyükafşar, Ph.D., Department of Pharmacology, Medical Faculty, Mersin University, Campus Yenişehir 33166 Mersin, Içel, Turkey. E-mail:kansu23{at}yahoo.com.
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↵1 Current address: Department of Pharmacology and Clinical Pharmacology, Medical Faculty, University of Ankara, 06100 Sıhhiye, Ankara, Turkey.
- Abbreviations:
- NO
- nitric oxide
- EFS
- electrical field stimulation
- GSNO
- S-nitrosoglutathione
- GTN
- glyceryl trinitrate
- L-ARG
- l-arginine
- L-NA
- l-NG-nitro-arginine
- L-NAME
- l-NG-nitro-arginine methyl ester
- L-NIO
- N-δiminoethyl-l-ornithine
- NO2-
- nitrite
- SNP
- sodium nitroprusside
- SOD
- superoxide dismutase
- Received November 3, 1998.
- Accepted April 23, 1999.
- The American Society for Pharmacology and Experimental Therapeutics
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