diethyl-maleate and Ischemia

Glutathione (GSH), present in a high concentration in the liver, serves important protective functions. We investigated the effect of lowered tissue GSH content, accomplished by diethylmaleate (DEM) administration, on liver extracellular GSH levels before and after global ischemia in anesthetized rats. Liver extracellular GSH levels were determined by microdialysis perfusion and an on-line high performance liquid chromatography system. Global liver ischemia was induced by ligation of the hepatic pedicles including the hepatic artery, portal vein, and bile duct. DEM (4 mmol/kg) significantly lowered both the liver tissue GSH levels (1.36 +/- 0.26 micromol/g wet wt vs 9.50 +/- 0.55 micromol/g wet wt for the untreated) and the liver extracellular GSH levels (4.3 +/- 2.4 microM vs 25.2 +/- 8.7 microM for the untreated). Global liver ischemia induced a dramatic increase in the liver extracellular GSH level. Although the liver tissue GSH level was lowered following DEM treatment, DEM administration did not affect significantly ischemia-induced elevation of extracellular GSH (when presented as fold increase relative to basal value). In conclusion, DEM showed a direct effect on liver extracellular GSH content in anesthetized rats. However, DEM treatment did not affect the relative release of GSH following global liver ischemia.

Topics: Anesthesia; Animals; Glutathione; Ischemia; Liver; Male; Maleates; Microdialysis; Rats; Rats, Sprague-Dawley

The role of oxygen-free radicals for metabolic derangements in the ischemic and reperfused liver is controversial. The effect on hepatic protein synthesis of a 60-minute period of ischemia followed by two hours of reperfusion was studied in four groups of rats with different hepatic contents of the oxygen free radical scavenger glutathione (GSH): group 1, fed rats; group 2, fed rats treated with diethylmaleate (DEM) one hour before use (0.69 mL/kg, i.p.); group 3, 48-hour fasted rats; and group 4, 48-hour fasted rats treated with cobalt-chloride (45 mg/kg, s.c.) ten hours before use. Protein synthesis rates were determined by measuring incorporation of U-14C-leucine into protein in incubated liver slices. Treatment of fed rats with DEM and fasting for 48 hours significantly reduced liver GSH content. The effect of fasting on liver GSH was reversed by treatment with cobalt-chloride. The protein synthesis rate was reduced to approximately 30% of initial value at the end of the ischemic period and recovered to 70% to 100% of initial value after two hours of reperfusion with no differences between the experimental groups. Thus the effect of liver ischemia and reperfusion on protein synthesis was similar in groups of rats with different hepatic GSH contents at the onset of ischemia. The data suggest that oxygen free radicals do not play a major role for the impairment of protein synthesis in the ischemic and reperfused liver.

Topics: Animals; Cobalt; Fasting; Glutathione; Ischemia; Leucine; Liver; Liver Glycogen; Male; Maleates; Protein Biosynthesis; Rats; Rats, Inbred Strains; Reperfusion Injury

Oxygen free radicals have been implicated as mediators of gastric mucosal injury caused by ischemia/reperfusion. We investigated the role of exogenous and endogenous glutathione (reduced glutathione, GSH) in gastric mucosal injury associated with hemorrhagic shock and reperfusion. Mucosal GSH content was found to be consistently higher in the antrum than in the corpus. Ischemia (hemorrhage to 25 to 30 mm Hg) followed by retransfusion of shed blood, but not ischemia alone, caused a marked drop in gastric mucosal GSH and gross mucosal injury, which was confined to the corpus and spared the antrum. Chemical depletion of gastric mucosal GSH with diethylmaleate or inhibition of GSH synthesis with buthionine sulfoximine increased mucosal injury in the corpus and also rendered the antral mucosa susceptible to ischemia/reperfusion injury. Pretreatment with exogenous GSH provided marked protection against gross mucosal ischemia/reperfusion injury and prevented the ischemia/reperfusion-induced drop in mucosal GSH. These data suggest that the mucosal availability of the antioxidant GSH is an important protective factor against the development of gastric mucosal ischemia/reperfusion injury and supports a major role of oxygen radical release in the pathogenesis of gastric ischemia/reperfusion injury.

Topics: Animals; Antimetabolites; Blood Transfusion; Buthionine Sulfoximine; Gastric Mucosa; Glutathione; Ischemia; Male; Maleates; Methionine Sulfoximine; Pyloric Antrum; Rats; Rats, Inbred Strains; Reperfusion Injury; Shock, Hemorrhagic; Stomach

The effect of the free radical scavenger glutathione (GSH) on the early post-ischemic liver cell death was studied on liver tissue of the rat. Animals with different pre-ischemic liver GSH contents were subjected to a 90 min period of ischemia, followed by a 3 h period of reperfusion. Cell death was evaluated morphologically by estimating intracellular calcium, using the stain Alizarin red S (ARS), and by dye-exclusion test using Evans blue. The extent of post-ischemic injury was also assessed by registration of the membrane potential (MP) in liver cells. Four groups of animals were studied: 1) fed rats. 2) fed rats pretreated with diethylmaleate. 3) rats fasted for 48 h. 4) fasted rats pretreated with cobalt-chloride. It was found that the early post-ischemic cell death was more extensive in rats with low initial GSH content (group 2 and 3), than in rats with high GSH content (group 1 and 4). It is suggested that GSH is protective against post-ischemic injury, probably by reducing lipid peroxidation.

Topics: Animals; Cell Survival; Fasting; Glutathione; Ischemia; Lipids; Liver; Liver Glycogen; Male; Maleates; Membrane Potentials; Perfusion; Rats; Rats, Inbred Strains