Biochemical examination on the increased superoxide dismutase-like plasma substance observed in a state of acute gastric mucosal lesions

Mechanisms underlying gastric antiulcerative activity of nitroxides in rats

Reactive oxygen-derived species and redox-active metals are implicated in mediation of the pathogenesis of gastric mucosal damage and ulceration. Therefore, common strategies of intervention employ metal chelators, antioxidative enzymes, and low-molecular-weight antioxidants (LMWA). The aim of the present study was to elaborate the mechanism(s) responsible for the protection provided by nitroxide radicals in the experimental model of gastric ulceration. Fasted male rats were treated ig with 1 ml 96% ethanol, with or without ig pretreatment with nitroxide or hydroxylamine. In several experiments, rats were injected ip or iv with iron(III) or iron(II) prior to ethanol administration. Rats were sacrificed 10 min after ethanol administration, the stomach was removed, washed and lesion area measured. Pretreatment with iron(III) complexed to nitrilotriacetate or citrate, aggravated the extent of the gastric injury. Conversely, iron(II) inhibited the formation of lesions. The nitroxides were rapidly reduced to their respective hydroxylamines and demonstrated antiulcerative activity for rats treated with iron. However, injecting the hydroxylamine resulted in a similar tissue distribution of nitroxide/hydroxylamnine but did not provide protection. The results show that: (a) the nitroxide radicals, rather than their respective non-radical reduced form, are the active species responsible for protection; (b) nitroxides protect by dismutating O2*- and possibly indirectly increasing the NO level; (c) unlike classical LMWA which are reducing agents, nitroxides inhibit gastric damage by acting as mild oxidants, oxidizing reduced metals and pre-empting the Fenton reaction; and (d) the nitroxides act catalytically as recycling antioxidants.

The role of cadmium in the peroxidative response of kidney to stress

Since the kidney is a main target for cadmium, its accumulation in the kidney tissue by increasing peroxidative damage make the kidney functions vulnerable to stress. For this reason, the effect of cadmium-induced peroxidative damage to kidney responses to stress was investigated in this study. Two-month-old albino rats receiving 15 micrograms/mL containing Cd drinking water for 30 d were exposed to restraint and cold stress for 6 h, and their responses were compared with those of unstressed counterparts. Lipid peroxidation was found to be significantly higher in the cortical portion of kidney in cadmium-exposed rats than that of unexposed animals. The mean thiobarbutyric acid reactive substance (TBARS) level rose from 211.6 +/- 64.2 to 303.4 +/- 46.4 nmol/g protein (p < 0.01). Six hours of cold and restraint stress caused an elevation in the cortical TBARS level in control animals without affecting its level in cadmium-exposed rats. Despite unaltered cortical TBARS, its medullar levels increased significantly in cadmium-exposed rats because of stress. These results suggested that cadmium accumulation in the kidney increases the susceptibility of medulla against peroxidative damage. However, further functional studies are necessary to explain the role of cadmium in the stress-induced deterioration of medullar functions.

The protective effect of copper complexes against gastric mucosal ulcer in rats

The study examines the anti-ulcer activity of Cu(I)-(nicotinic acid)2Cl [CuCl(HNA)2]. A dose of 8 mg (23 mumol) of complex/kg body mass was suspended in 0.25% Tween-80 in saline solution and administered intragastrically to male Wistar albino rats which had developed gastric ulcers as a result of pyloric ligation (Shay-rat model). Another group of animals received 5 mg (25 mumol)/kg body mass of the copper-glycinate complex Cu(II)(glycinate)2 [Cu(II)(Gly)2]. Both protected as shown by reduction in the ulcer index, inhibition of gastric perforation and death. Significant increases in gastric juice volume and superoxide dismutase (SOD) activity in the gastric mucosa and blood plasma were found with both copper complexes, while the gastric juice prostaglandin E2 (PGE2) content was significantly decreased in the Cu(II)(Gly)2-treated group, it was significantly increased in the gastric mucosa of the CuCl(HNA)2-treated group. The copper complex-treated animals, especially those which received Cu(II)(Gly)2 had a marked fall in thromboxane A2 (TXA2) levels. These results suggest that intragastric administration of either CuCl(HNA)2 or Cu(II)(Gly)2 produced anti-ulcerogenic activity, with different modes of action.