Endogenous Sulfhydryl Compounds Research Articles

Gastroprotective Effects of Paeonia Extract Mixture HT074 against Experimental Gastric Ulcers in Rats.

Background Paeonia extract mixture HT074 is a standardized multiherbal mixture comprising extracts from Inula britannica flowers and Paeonia lactiflora roots, which are used to treat digestive disorders in traditional Korean medicine. This study was focused on elucidating the underlying mechanisms of the gastroprotective effects of HT074 in different gastric ulcer models. Methods Gastric lesions were induced in rats by an HCl/EtOH solution, water immersion-restraint stress (WIRS), and indomethacin. Gastric secretions were studied in pylorus-ligated rats, while mucus secretions were assessed by measuring alcian blue-binding capacity of mucus in the rat model of HCl/EtOH-induced gastric ulcer. Additionally, the involvement of nitric oxide (NO) and sulfhydryl compounds in HT074-mediated mucosal protection was elucidated using their inhibitors, i.e., N G-nitro- L-arginine methyl ester hydrochloride (L-NAME) and N-ethylmaleimide (NEM), respectively. Furthermore, the effects on indomethacin-induced cell death and prostaglandin E2 (PGE2) levels were assessed in AGS cells. Results Oral administration of HT074 significantly decreased gastric lesions induced by HCl/EtOH, WIRS, and indomethacin. Furthermore, it significantly decreased the volume, acidity, and total acidity of gastric juice in pylorus-ligated rats and increased the alcian blue-stained gastric mucus in HCl/EtOH-induced gastric ulcer in rats. Pretreatment with NEM abolished the gastroprotective effects of HT074, while L-NAME did not. In AGS cells, HT074 significantly reduced indomethacin-induced cell death and increased the PGE2 levels. Conclusions These findings suggest that HT074 has gastroprotective effects against various ulcerogens, including HCl/EtOH, immersion stress, and NSAIDs. These effects are attributed to the inhibition of gastric secretions and preservation of the gastric mucosal barrier by increased mucus production, which is partially mediated through endogenous sulfhydryl compounds and PGE2. Based on these findings, we propose that HT074 may be a promising therapeutic agent for gastritis and gastric ulcer.

The Protective Potential of Phyllanthus niruri and Corilagin on Gastric Lesions Induced in Rodents by Different Harmful Agents.

The gastroprotective effect of the methanol extract of Phyllantus niruri and its main constituent, corilagin, were studied in vivo. The extract (50, 125, or 250 mg/kg, p. o.) inhibited ethanol-induced lesions in rats by 43 % (p < 0.001), 69 % (p < 0.001), and 99 % (p < 0.001), respectively. It also inhibited the formation of indomethacin-induced gastric ulcers in rats by 80 % (p < 0.01), 89 % (p < 0.01), and 97 % (p < 0.01). A decrease in lipid hydroperoxide levels (p < 0.01) and in myeloperoxidase activity (p < 0.05) evidenced a reduction of oxidative damage and neutrophil infiltration in gastric tissues from ulcerated mice using ethanol/HCl. Potent in vitro free radical scavenger activity (IC50 = 0.07) using the DPPH assay was observed. In contrast, the extract (250 mg/kg, i. d.) did not show antisecretory activity in pylorus-ligated rats, and also failed to inhibit the H+,K+-ATPase activity in vitro. However, in pylorus-ligated rats, the extract (50, 125, and 250 mg/kg, i. d.) increased adhered mucus content by 22 % (p < 0.05), 28 % (p < 0.01), and 38 % (p < 0.01), respectively. The involvement of prostaglandins, nonprotein endogenous sulfhydryl compounds, α2-receptors, and endogenous nitric oxide in the gastroprotection elicited by the extract was also evaluated. Finally, corilagin reduced the lesion area of ethanol-induced gastric ulcers in mice by 88 % (30 mg/kg, p. o.; p < 0.001). Based on these results, it has been concluded that P. niruri methanol extract possesses gastroprotective activity by different and complementary pathways, which together promote an improvement in gastric cytoprotection. The presence of corilagin may partially explain the effectiveness of the extract against gastric damage.

Byrsonima intermedia A. Juss.: Gastric and duodenal anti-ulcer, antimicrobial and antidiarrheal effects in experimental rodent models

Ethnopharmacological relevanceAn ethnopharmacological survey indicated that the leaves of Byrsonima intermedia A. Juss. (Malpighiaceae), a medicinal species commonly found in the Brazilian Cerrado, can be used against gastroduodenal disorders, such as gastric ulcers and diarrhea. Aim of the studyThe objective of this study was to evaluate the effects of a methanolic extract of Byrsonima intermedia (MBI) leaves on gastric and duodenal ulcers and to assess the antimicrobial and antidiarrheal effects of this extract. Material and methodsThe anti-ulcerogenic effect of MBI was investigated with different ulcerogenic agents in rodents (mice and rats), including non-steroidal anti-inflammatory drug (NSAID), HCl/ethanol, pyloric ligature, absolute ethanol, cysteamine and ischemia–reperfusion. The gastroprotective effect of MBI was assessed by analysing the volume of gastric juice, pH, total acidity, mucus, NO, sulfhydryl compound, vanilloid receptor, glutathione (GSH) levels, and myeloperoxidase (MPO) activity in the gastric and duodenal mucosa. The gastric and duodenal healing effects of MBI were also evaluated during 7 or 14 days of treatment. The antidiarrheal action (measured by intestinal motility and diarrhea induced by castor oil) and anti-bacterial action of MBI against Staphylococcus aureus, Escherichia coli and Helicobacter pylori were also evaluated by microdilution methods. ResultsThe phytochemical profile from MBI indicated the presence of phenolic acids, flavan-3-ols, oligomeric proanthocyanidins, and flavonoids. MBI (500mg/kg, p.o.) significantly inhibited totally gastric and duodenal lesions (69%) and healed gastric (49% on 14 days) and duodenal lesions (45% on 7 and 14 days). The MBI exert gastroprotective action by participation of endogenous sulfhydryl compounds, vanilloid receptors and increase in GSH level to effective gastric and duodenal protection. MBI also displayed curative (42%) and preventive (49%) antidiarrheal effects by involvement of opiate receptors and also antimicrobial effects in vitro. ConclusionsByrsonima intermedia leaves present gastroprotective, healing and antidiarrheal activities, supporting previous claims that its traditional use can treat gastrointestinal disorders.

The anti-ulcerogenic effects of Curatella americana L.

Ethnopharmacological relevance: Curatella americana L. (Dilleneaceae) is a medicinal plant very frequently cited as acting against gastrointestinal disorders in ethnopharmacological inventories of the Cerrado region of Brazil. Aim of the study The ethanolic extract (CEB) and infusion (BI) of Curatella americana bark were investigated for their ability to prevent and heal ulceration of the gastric mucosa. Materials and methods The preventive and healing actions of Curatella americana were evaluated in experimental in vivo models in rodents that simulated this disease in human gastric mucosa. Results CEB significantly decreased the severity of gastric damage formation induced by the combination of several gastroprotective models (HCl/ethanol, indomethacin/bethanecol, absolute ethanol, stress and pylorus ligature). But, unlike CEB, the BI did not exert gastroprotective effect. The gastroprotective action of CEB involved antisecretory action, augmentation of gastric mucus (48%) and participation of endogenous sulfhydryl compounds that increase efficacy of barrier mucosa against injurious agents. CEB also presents effective healing action in chronic gastric disease (1.90 ± 0.55 vs. 6.86 ± 0.46 mm 2 in the control) and its action mechanisms consisted of increasing the PGE 2 (40%) and somatostatin levels (269%) while decreasing the gastrin level in rat plasma (79%). Conclusions The gastroprotective effect and healing action of Curatella americana involved modulation of PGE 2, somatostatin and gastrin levels, probably due to the presence of oligomeric and polymeric proanthocyanidins in the bark.

Constituents and Antiulcer Effect of Alchornea glandulosa: Activation of Cell Proliferation in Gastric Mucosa during the Healing Process

Alchornea glandulosa (Euphorbiaceae) is a plant used in folk medicine as an antiulcer agent. Rats pretreated with methanolic extract obtained from the leaves of A. glandulosa (AG) showed a dose-dependent effect and significant reduction of gastric ulcers induced by absolute ethanol at the doses of 500 (57%) and 1000 mg/kg (85%) in relation to the control group. Pretreatment of mice with AG (500, 1000 mg/kg, p.o.) showed dose-dependent activity and significantly decreased the severity of lesions caused by HCl/ethanol and by non steroidal anti inflammatory drug-induced gastric lesions. Pretreatment with AG also induced antisecretory action via local and systemic routes and a significant decrease in the total gastric acid content. The gastroprotective effects of AG involved the participation of nitric oxide and increased levels of endogenous sulfhydryl compounds, which are defensive mechanisms of the gastrointestinal mucosa against aggressive factors. The ability of AG to heal gastric ulcers was evaluated after 14 consecutive days of treatment. The results showed that single oral administrations of AG (250 mg/kg/once daily) potently stimulates gastric epithelial cell proliferation that contributes to the accelerated healing of gastric ulcers induced by acetic acid. In addition, no subacute toxicity (body weight gain, vital organs, and serum biochemical parameters) was observed during treatment with AG. Phytochemical investigation of AG led to the isolation of myricetin-3-O-alpha-L-rhamnopyranoside, quercetin-3-O-alpha-L-arabinopyranoside, quercetin-3-O-beta-D-galactopyranoside, quercetin, amentoflavone, methyl gallate, gallic acid, and pterogynidine. We also established the phytochemical profile of AG with the quantification of total phenolic compounds. These compounds may contribute to the observed antiulcerogenic effects of AG.

Anti-ulcerogenic and anti-inflammatory activity of the methanolic extract of Larrea divaricata Cav. in rat

Larrea divaricata Cav. (Zygophyllaceae) is used in popular medicine as anti-inflammatory and anti-rheumatic drug, containing higher amounts of nordihydroguaiaretic acid, a well-known free radical scavenger. Here we describe the gastric anti-ulcerogenic effect of the methanolic extract of Larrea divaricata ( LdME) leaves in rat, using absolute ethanol and HCl 0.6N as necrotizing agents, and the effect of blocking endogenous sulfhydryl (SH) groups with N-ethylmaleimide (NEM). We also studied the anti-inflammatory activity of LdME in two rat experimental models: cotton pellet induced granuloma and arthritis induced by adjuvant-carrageenan. Influence of treatment in body weight and some lymphoid organs was evaluated. Finally, the free radical scavenging capacity of LdME was determined by the method of 1,1-diphenyl-2-picrylhydrazyl (DPPH) inhibition. LdME demonstrated anti-ulcerogenic effect in rats, and it was shown that the endogenous SH compounds were not involved in the mechanism of action. LdME also showed inhibitory activity in the applied models of inflammation, being more effective in the acute phase. No effect was observed concerning the weight of spleen, thymus and body. The extract proved to possess elevated free radical scavenging capacity which may contribute to the observed gastric anti-ulcerogenic and anti-inflammatory activity.

Cytoprotective effect of NC-1300-O-3 against gastric lesions induced by necrotizing agents in rats.

The cytoprotective effect of NC-1300-O-3 and its mechanism of action were investigated. NC-1300-O-3 at doses of 3 and 10 mg/kg, p.o. significantly prevented the formation of gastric lesions by HCl.ethanol in rats, and its efficacy was not influenced by repeated administration for up to 4 weeks. The interaction between NC-1300-O-3 and necrotizing agents in the stomach, which is considered to be related to the development of cytoprotection, was not observed. A preventive effect of NC-1300-O-3 against gastric lesions was observed at the same dose even when gastric secretion was completely inhibited by pretreatment with omeprazole. This suggests that the cytoprotective effect of NC-1300-O-3 is an action on the gastric mucosa independent of its antisecretory effect. The cytoprotective effect of NC-1300-O-3 was not affected by pretreatment with indomethacin but was partly decreased by N-ethylmaleimide pretreatment, suggesting the participation of endogenous sulfhydryl compounds in the action of NC-1300-O-3. This compound dose-dependently increased the hexosamine content in the gastric lumen in rats at a dose range of 3-30 mg/kg, p.o. and slightly inhibited a reduction in surface mucus and mucosal hexosamine content caused by necrotizing agents. Moreover, NC-1300-O-3 at doses of 10 and 30 mg/kg, p.o. significantly inhibited the increased gastric vascular permeability caused by alcohol treatment; and at 30 mg/kg, p.o., it inhibited the reduction in potential difference caused by aspirin in rats. These actions were suggested to contribute to the cytoprotective effect of NC-1300-O-3.

Roles of sulfhydryl compounds in the gastric mucosal protection of the herb drugs composing oren-gedoku-to (a traditional herbal medicine).

We investigated the involvement of sulfhydryl compounds in the cytoprotective effect of each component herb drug composing Oren-gedoku-to (OGT) against ethanol-induced gastric lesions and potential difference (PD) reduction in comparison with that of OGT in rats. Pretreatment with N-ethylmaleimide (NEM) significantly blocked the cytoprotective effects of OGT, Coptidis rhizoma and Phellodendri cortex, but did not block the cytoprotective effects of Gardeniae fructus and Scutellariae radix. The inhibitory effects of OGT, Coptidis rhizoma and Phellodendri cortex against the PD reduction disappeared in the presence of NEM or diethyldithiocarbamate (DDC), whereas NEM or DDC had little or no effect with Gardeniae fructus and Scutellariae radix. These results suggest that the gastric mucosal protection of Coptidis rhizoma and Phellodendri cortex may be ascribed to the reinforcement of mucosal barrier resistance through endogenous sulfhydryl compounds and DDC-sensitive compounds, but those of Gardeniae fructus and Scutellariae radix may be independent of NEM- or DDC-sensitive compounds.

The Protective and Therapeutic Mechanisms of Sucralfate

Sucralfate is a nonsystemic agent that is effective in protecting the gastroduodenal mucosa against injury. In addition, sucralfate is effective in the healing of acute duodenal and gastric ulceration, the therapy of esophagitis, and the prevention of ulcer recurrence. The mechanisms responsible for sucralfate's successful protective and therapeutic actions include the adsorption of pepsin and bile acids, the stimulation of bicarbonate and mucus secretion, and stimulation of endogenous synthesis of prostaglandins. When sucralfate is given to experimental animals or humans, it stimulates endogenous synthesis and release of prostaglandin E2 and inhibits thromboxane release. Pretreatment of animals with the cyclooxygenase inhibitor indomethacin results in a marked decrease in the protective effect of sucralfate against alcohol injury. Sucralfate also increases epidermal growth factor binding to ulcerated areas and stimulates macrophage activity. In addition, sucralfate stimulates endogenous sulfhydryl compounds. At the microscopic level sucralfate protects the vascular integrity of the mucosa and the mucosal proliferative zone. It also stimulates epithelial cell restitution and stimulates cell proliferation. The administration of sucralfate before acute injury results in decreased depth and extent of injury and in acceleration of healing. Because of sucralfate's ability to stimulate the protective and reparative mechanisms of the gastric and duodenal mucosa, it is an important nonsystemic agent for the therapy and prevention of peptic ulceration.

Involvement of cellular sulfhydryl compounds in the inhibition of rna synthesis by selenite

Selenite has been shown previously to inhibit cellular RNA synthesis. Based upon our previous observation that selenite inhibits purified RNA polymerase only in the presence of a sulfhydryl compound (Frenkel et al., Mol Pharmacol 31: 112–116, 1987), we hypothesized that the inhibition of cellular RNA synthesis by selenite involves endogenous sulfhydryl compounds. We found that depletion of cells of endogenous sulfhydryl compounds, by exposure to diethylmaleate (DEM), virtually eliminated the inhibitory effect of a 1-hr exposure of cells to selenite. This inhibition was restored to normal or higher levels when the selenite was reacted with glutathione or cysteamine prior to addition to the DEM-treated cells. RNA synthesis in DEM-treated cells was inhibited after a 4-hr exposure to higher concentrations of selenite. In contrast to the effect of DEM, specific depletion of the cells of glutathione, by exposure to buthionine sulfoximine, had no effect on the inhibition of RNA synthesis by selenite. These results demonstrate the involvement of endogenous cellular sulfhydryl compounds in the inhibition of RNA synthesis by selenite, but indicate that glutathione, in particular, is not involved in this inhibition.

A Possible Mechanism for the Gastric Mucosal Protection by Oren-Gedoku-To (OGT), a Traditional Herbal Medicine

We investigated the involvement of sulfhydryl-compounds in the cyto-protective effect of Oren-gedoku-to (OGT) against ethanol-induced gastric lesions and potential difference (PD) reduction in comparison with those of sucralfate and glutathione in rats. Pretreatment with indomethacin (IND) had little influence on the cytoprotective effects of OGT and glutathione, but attenuated the effect of sucralfate. Pretreatment with N-ethylmaleimide (NEM) blocked the cytoprotective effects of these three drugs. Pretreatment with lodoacetamide diminished the cytoprotection of OGT and glutathione, but had little effect on that of sucralfate. The cytoprotective activities of OGT, glutathione and sucralfate were little affected by pretreatment with 6.6′-dithiodinicotinic acid. The inhibitory effects of OGT and glutathione against the PD reduction were completely blocked by pretreatment with NEM, while they were not influenced by pretreatment with IND. On the other hand, the inhibitory effect of sucralfate disappeared both by IND and NEM. These results suggest that the cytoprotective effect of OGT may be mediated by endogenous sulfhydryl compounds, but not by endogenous prostaglandins in the gastric mucosa.

A possible mechanism for the gastric mucosal protection by oren-gedoku-to (OGT), a traditional herbal medicine.

We investigated the involvement of sulfhydryl-compounds in the cytoprotective effect of Oren-gedoku-to (OGT) against ethanol-induced gastric lesions and potential difference (PD) reduction in comparison with those of sucralfate and glutathione in rats. Pretreatment with indomethacin (IND) had little influence on the cytoprotective effects of OGT and glutathione, but attenuated the effect of sucralfate. Pretreatment with N-ethylmaleimide (NEM) blocked the cytoprotective effects of these three drugs. Pretreatment with iodoacetamide diminished the cytoprotection of OGT and glutathione, but had little effect on that of sucralfate. The cytoprotective activities of OGT, glutathione and sucralfate were little affected by pretreatment with 6,6'-dithiodinicotinic acid. The inhibitory effects of OGT and glutathione against the PD reduction were completely blocked by pretreatment with NEM, while they were not influenced by pretreatment with IND. On the other hand, the inhibitory effect of sucralfate disappeared both by IND and NEM. These results suggest that the cytoprotective effect of OGT may be mediated by endogenous sulfhydryl compounds, but not by endogenous prostaglandins in the gastric mucosa.

Protection of gastric epithelial cell monolayers from a human cell line by omeprazole in vitro.

Omeprazole has an anti-ulcerogenic effect and protects rat gastric mucosa against drug-induced damage in vivo. We have evaluated omeprazole protection against damage induced by sodium taurocholate to gastric epithelial cell monolayers, an experimental model that completely excludes the influence of systemic factors. Furthermore, since our model consists of mucus-producing cells, the acid inhibitory effect of the drug in any protection is negligible. The role of prostaglandin and sulfhydryls in any such protection has also been evaluated. Monolayers of gastric cells from a well-differentiated human cell line were studied. A chromium-51 release assay was used to assess cell damage. Sodium taurocholate damaged cells dose-dependently (r = 0.97, p less than 0.01). Pretreatment with omeprazole significantly reduced the amount of cell damage brought about by sodium taurocholate (p less than 0.001). Indomethacin did not prevent the protection afforded by omeprazole, nor did incubation with omeprazole increase the amount of prostaglandin E2 produced by cultured cells. Omeprazole did not increase the amount of sulfhydryl compounds in cultured cells. These results indicate that omeprazole protects gastric cells independently of systemic factors and of inhibition of gastric acid secretion. This protection is not related to stimulation of prostaglandin synthesis nor is it associated with an increase of endogenous sulfhydryl compounds.

Cytoprotective Effects of NC-1300 and Omeprazole on HCl⋅Ethanol-Induced Gastric Lesions in Rats

NC-1300 (10–100 mg/kg), given p.o. at 0.5, 6, 12 or 24 hr before HCl-ethanol, dose-dependently protected the rat gastric mucosa. This protection was observed even when the gastric contents had been removed before application of HCl-ethanol. NC-1300 (30 mg/kg), given i.p., was without effect on lesion formation in a dose which potently inhibited gastric acid secretion in pylorus-ligated rats. Pretreatment with indomethacin (5 mg/kg, s.c.) resulted in no reduction in the protection by NC-1300, excluding the possible participation of endogenous prostaglandins in the protective mechanism. N-ethylmaleimide pretreatment (10 mg/kg, s.c.) slightly reduced the protective activity of NC-1300, suggesting the partial participation of endogenous sulfhydryl compounds in the NC-1300 protection. NC-1300 sulfide and mercaptobenzimidazole (compounds obtained after mixing NC-1300 with acidic solution) also dose-dependently protected against HCl⋅ethanol-induced lesions when given p.o. at 0.5 hr before HCl⋅ethanol. The protection was significant but was considerably reduced in contrast to NC-1300 when the compounds were given 12 hr beforehand. NC-1300 sulfone had no effect on lesion formation. Omeprazole (10, 30 mg/kg), given p.o., also dose-dependently inhibited HCl⋅ethanol-induced lesions. However, the duration of protection was shorter than that seen with NC-1300, i.e., the effect disappeared 12 hr later. Thus, NC-1300 has a potent and long-lasting activity on HCl⋅ethanol-induced gastric lesions. The mechanism by which this occurs remains unknown.

Role of sulfhydryls in the hepatotoxicity of organic and metallic compounds

Endogenous sulfhydryl compounds serve a critical role in maintaining the function and viability of living systems. Glutathione (GSH) is the most abundant of these nonprotein thiols. During the past decade it has been demonstrated that sulfhydryls such as GSH also serve an important role in protecting vital nucleophilic sites in the liver from electrophilic attack by numerous classes of reactive chemicals. Organocompounds such as bromobenzene and acetaminophen which undergo microsomal metabolism yield reactive intermediates that are specifically inactivated by conjugation with sulfhydryls in the form of GSH. Thus, for organocompounds GSH is extremely important in protecting against toxic insults. More recently, other sulfhydryl compounds also have been found to serve a specific but as yet less defined role in protecting biological systems against chemically induced injury. Metals such as cadmium have a high affinity for sulfhydryls and the metal binding protein metallothionein binds cadmium with high affinity. The highly specific association of the metal with this sulfhydryl-enriched protein serves to effectively sequester the reactive cadmium ion. The central role of sulfhydryl equivalents in the detoxication of organo- and metallocompounds is similar; however, the mechanism by which this is achieved is fundamentally different.

Role of Sulfhydryls in the Hepatotoxicity of Organic and Metallic Compounds

Role of Sulfhydryls in the Hepatotoxicity of Organic and Metallic Compounds. KLAASSEN, C. D., BRACKEN, W. M., DUDLEY, R. E., GOERING, P. L., HAZELTON, G. A., AND HJELLE, J. J. (1985). Fundam. Appl. Toxicol.. 5,806-815. Endogenous sulfhydryl compounds serve a critical role in maintaining the function and viability of living systems. Glutathione (GSH) is the most abundant of these nonprotein thiols. During the past decade it has been demonstrated that sulfhydryls such as GSH also serve an important role in protecting vital nucleophilic sites in the liver from electrophilic attack by numerous classes of reactive chemicals. Organocompounds such as bromobenzene and acetaminophen which undergo microsomal metabolism yield reactive intermediates that are specifically inactivated by conjugation with sulfhydryls in the form of GSH. Thus, for organocompounds GSH is extremely important in protecting against toxic insults. More recently, other sulfhydryl compounds also have been found to serve a specific but as yet less defined role in protecting biological systems against chemically induced injury. Metals such as cadmium have a high affinity for sulfhydryls and the metal binding protein metallothionein binds cadmium with high affinity. The highly specific association of the metal with this sulfhydryl-enriched protein serves to effectively sequester the reactive cadmium ion. The central role of sulfhydryl equivalents in the detoxication of organc- and metallocompounds is similar, however, the mechanism by which this is achieved is fundamentally different.

EFFECT OF POLYAMINES ON ACIDIFIED ETHANOL-INDUCED GASTRIC LESIONS IN RATS

The participation of polyamines and nonprotein sulfhydryls in the gastric cytoprotective mechanisms was studied using gastric mucosal lesions produced by acidified ethanol in rats as an experimental model. Treatment with prostaglandin E2 (PGE2), but not cimetidine, prevented the formation of gastric mucosal lesions. Oral administration of cadaverine, spermidine and spermine prevented the lesion formation by acidified ethanol in a dose-dependent manner. Indomethacin or acetazolamide had no influence on the cytoprotective effect of spermine, whereas sulfhydryl blockers such as iodoacetamide and N-ethylmaleimide partially blocked it. Sulfhydryl compounds such as cysteine, reduced glutathione (GSH), and cystcamine prevented the lesion formation induced by acidified ethanol. The concentration of nonprotein sulfhydryls in the gastric mucosa was significantly decreased at 1 hr after administration of acidified ethanol, and this decrease was partially prevented by spermine or PGE2. These results suggest that the cytoprotective effect of spermine may not be mediated by endogenous prostaglandins or alkaline secretion in the gastric mucosa, but may be partially related to endogenous sulfhydryl compounds.

Effect of polyamines on acidified ethanol-induced gastric lesions in rats.

The participation of polyamines and nonprotein sulfhydryls in the gastric cytoprotective mechanisms was studied using gastric mucosal lesions produced by acidified ethanol in rats as an experimental model. Treatment with prostaglandin E2 (PGE2), but not cimetidine, prevented the formation of gastric mucosal lesions. Oral administration of cadaverine, spermidine and spermine prevented the lesion formation by acidified ethanol in a dose-dependent manner. Indomethacin or acetazolamide had no influence on the cytoprotective effect of spermine, whereas sulfhydryl blockers such as iodoacetamide and N-ethylmaleimide partially blocked it. Sulfhydryl compounds such as cysteine, reduced glutathione (GSH), and cysteamine prevented the lesion formation induced by acidified ethanol. The concentration of nonprotein sulfhydryls in the gastric mucosa was significantly decreased at 1 hr after administration of acidified ethanol, and this decrease was partially prevented by spermine or PGE2. These results suggest that the cytoprotective effect of spermine may not be mediated by endogenous prostaglandins or alkaline secretion in the gastric mucosa, but may be partially related to endogenous sulfhydryl compounds.

High-performance liquid chromatographic determination of penicillamine in whole blood, plasma, and urine

A high-performance liquid chromatographic method for the determination of penicillamine in plasma, whole blood, and urine samples is described. The method uses a commercially available electrochemical detector at a potential of +0.1 V versus the Ag/AgCl reference electrode. This method is selective and sensitive for sulfhydryl compounds. The chromatography separates penicillamine from other endogenous sulfhydryl compounds with a limit of detection for penicillamine in biological samples of ca. 10 −7 M.

In vitro studies on the metabolic pathway of SQ 14225 (Captopril) and mechanism of mixed disulfide formation.

The metabolic pathway of SQ 14225 (Captopril) and the mechanism of the mixed disulfide formation with endogenous sulfhydryl compounds were studied in in vitro cell free systems. In the rat liver 9000 x g supernatants, SQ 14225-14C was metabolized to one major metabolite, glutathione-SQ 14225 mixed disulfide (GSSQ), and two minor metabolites including SQ 14551, a symmetrical disulfide of SQ 14225. The formation of GSSQ was markedly accelerated by the addition of oxidized glutathione (GSSG), but not affected by the addition of reduced glutathione (GSH), indicating that GSSQ was formed by the thiol-disulfide interchange between SQ 14225 and GSSG. Although the thiol-disulfide interchange was also observed between SQ 14225 and L-cystine, L-homocystine and SQ 14551 as well as GSSG, only the formation of GSSQ was a rapid reaction and markedly decreased by heat treatment of the liver 9000 x g supernatants. These findings demonstrate that the formation of GSSQ is catalyzed by a GSSG specific enzyme which is supposed to be thioltransferase (Glutathione: Disulfide Oxidoreductase). Although GSSQ was stable in the rat liver 9000 x g supernatants, it was rapidly hydrolyzed to cysteine-SQ 14225 mixed disulfide (CySSQ) in the rat kidney 9000 x g supernatants. A specific inhibitor of gamma-glutamyltranspeptidase, anthglutin, inhibited the hydrolysis. GSSQ-14C administered to a beagle dog was excreted into the urine in the form of CySSQ. Thus, it was speculated that CySSQ excreted into the urine as a major metabolite of SQ 14225 was derived from GSSQ formed in the liver followed by hydrolysis in the kidney.