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At least 73 records · Page 4Linked to original sources
PubMed1992

Action profiles of nitric oxide, S-nitroso-L-cysteine, SNP, and NANC responses in opossum lower esophageal sphincter.

Circular muscle strips from opossum lower esophageal sphincter were suspended in organ baths for measurement of isometric tension. Nonadrenergic noncholinergic (NANC) inhibitory nerves were stimulated by means of transmural field stimulation. This induced frequency-dependent relaxations of the muscle strips. Methylene blue (3 x 10(-6) M; inhibits guanylate cyclase) and pyrogallol (10(-4) M; generates superoxide anions) had no influence on relaxations, whereas oxyhemoglobin [10(-5) M; binds nitric oxide (NO) and other nitroso compounds extracellularly] inhibited relaxations at all frequencies. NO concentration dependently relaxed the muscle strips. Pyrogallol (10(-4) M) and methylene blue (3 x 10(-6) M) inhibited and oxyhemoglobin (10(-5) M) nearly abolished relaxation induced by NO. S-nitroso-L-cysteine caused concentration-dependent relaxations of the muscle strips, which were inhibited by pyrogallol (10(-4) M), whereas methylene blue (3 x 10(-6) M) augmented the action of S-nitroso-L-cysteine. Methylene blue (3 x 10(-6) M) had no influence on the concentration-dependent relaxations caused by sodium nitroprusside (SNP). Oxyhemoglobin (10(-5) M), and to a lesser extent pyrogallol (10(-4) M), both inhibited the effects of SNP. The action profiles for S-nitroso-L-cysteine, NO, and SNP differed from the action profile for NANC nerve-mediated response. Although pyrogallol inhibited the effects of SNP, the action profile generally resembled the action profile for NANC responses more closely than did the profiles for S-nitroso-L-cysteine or NO. In conclusion, of the nitroso compounds studied, SNP most closely resembled the response to NANC nerve stimulation. Neither NO nor S-nitroso-L-cysteine individually mimicked the NANC response.

Animals↗
PubMed1992

Endothelium-dependent tolerance to ethanol-induced contraction of rat aorta: effect of inhibition of EDRF action and nitric oxide synthesis.

In vitro ethanol induces a dose-dependent contraction of the aorta. Tolerance to this effect of ethanol is expressed by a rightward shift of the dose-response curve in aorta from animals intoxicated with ethanol for 2 days. The expression of tolerance in the aorta is dependent upon the presence of functional endothelial cells which suggests that tolerance is mediated, in part, by endothelium-derived relaxing factor (EDRF). To test this hypothesis, three inhibitors of EDRF action and an inhibitor of nitric oxide synthesis were studied for their ability to alter tolerance to ethanol-induced contraction of the aorta. In vitro pretreatment of aortic rings with gossypol (10(-6)-10(-5) M), pyrogallol (10(-5) M), hemoglobin (10(-6) M), and NG-nitro-L-arginine (NOARG, 10(-4) M) inhibited endothelium-dependent relaxation induced by carbachol. The inhibition of carbachol-induced relaxation produced by pyrogallol was reversed by superoxide dismutase (SOD, 45 units/ml). In vitro pretreatment of rings obtained from ethanol-treated rats with gossypol, pyrogallol, hemoglobin, or NOARG inhibited the expression of ethanol tolerance, shifting the ethanol dose-response curve to control values. SOD reversed the effect of pyrogallol pretreatment. None of the antagonists significantly altered the ethanol dose-response curve of aortic rings obtained from control animals. These data support the hypothesis that tolerance to ethanol-induced contraction of the aorta is mediated by the release of EDRF from endothelial cells.

Animals↗
PubMedDate not supplied

[Possibilities for the deep bacterial destruction of 2,4,6-trinitrotoluene].

The possibility of 2,4,6-trinitrotoluene (TNT) deep destruction (the aromatic cycle fission inclusive) by Pseudomonas fluorescens B-3468 is reported for the first time. The formation of nitrogen-free metabolites, viz. phloroglucinol and pyrogallol, is preceded by the NAD(P)H-dependent deamination of 2,4-diamino-6-nitrotoluene (2,4-DA), a TNT intermediate. 30% of 2,4-DA nitrogen in released as ammonium under the action of an induced cell-free extract in the presence of the preferential co-factor NADH (together with FAD). The elevated pyrogallol-decomposing activity in cells grown on 2,4-DA, phloroglucinol and pyrogallol as well as the induction of the pyrocatechase activity in cells grown on the above substrates, together with the earlier reported accumulation of phloroglucinol and pyrogallol upon 2,4-DA utilization, indicated that the enzyme might be involved in the TNT cycle cleavage. The participation of NADH-dependent glutamate dehydrogenase in 2,4-DA nitrogen utilization is supported by experimental evidence.

Biodegradation, Environmental↗