Effect of chronic ethanol administration on energy metabolism and phospholipase A2 activity in rat liver

Abstract

1. For a period of 31 days male rats were given a liquid diet containing 36% of its energy as ethanol. Liver mitochondria from these animals demonstrated lowered respiratory control with succinate as substrate, a diminished energy-linked anilinonaphthalene-sulphonic acid fluorescence response, and lowered endogenous ATP concentrations. The phospholipid/protein ratio in mitochondria from these animals was unchanged; only minor alterations in the phospholipid fatty acid composition were observed. 2. In experiments where mitochondria were incubated at 18 degrees C in iso-osmotic sucrose (aging experiments), the above energy-linked properties were lost at an earlier time in organelles from ethanol-fed animals. Phospholipase A2 acitivty was depressed in mitochondria from control animals until respiratory control was lost and ATP was depleted. In contrast, no lag in the expression of phospholipase activity was observed in mitochondria from ethanol-fed rats. This loss of control of the phospholipase resulted in an earlier degradation of membrane phospholipids under the conditions of the aging experiments. 3. The ATPase (adenosine triphosphatase) activities, measured in freshly prepared tightly coupled mitochondria and in organelles uncoupled with carbonyl cyanide p-trifluoromethoxyphenylhydrazone, were not significantly different in ethanol-fed and liquid-diet control animals. When the mitochondria were aged at 18 degrees C, the activity increased with time of incubation in organelles from both groups of animals. A lag was observed, however, as the ATPase activity increased in control preparations. This lag was not present as APTase activity increased in mitochondria from ethanol-fed animals. 4. The significantly lowered values observed for energy-linked functions with succinate as an energy source demonstrate that ethanol elicits an alteration in liver mitochondria that affects the site II-site III regions of the oxidative-phosphorylation system. The apparent lack of control of the phospholipase A2 and ATPase activities in mitochondria from ethanol-fed animals suggests that the membrane microenvironment of these enzymes has been altered such that they can exert their catabolic effects more readily under conditions of mild perturbation. The fatty acid analyses demonstrate that the observed alterations both in the energy-linked functions and in control of the phospholipase and ATPase are not mediated through changes in the acyl chain composition of bulk-phase phospholipids.

Chronic Ethanol Consumption Alters the Glutathione/Glutathione Peroxidase‐1 System and Protein Oxidation Status in Rat Liver

“…The RCRs measured in mitochondria isolated from control-and ethanol-fed rats were 5.2 Ϯ 0.3 and 4.2 Ϯ 0.2 (p ϭ 0.007; n ϭ 5), respectively, when glutamate/malate were used as oxidizable substrates. Moreover, the RCR was similarly depressed in mitochondria from ethanol-fed rats when succinate was used as the oxidizable substrate (control, 4.25 Ϯ 0.3; ethanol, 3.5 Ϯ 0.2; p ϭ 0.006; n ϭ 5) which is in agreement with previous findings (Spach et al, 1979).…”

“…Protease inhibitors [phenylmethylsulfonyl fluoride (40 g/mL), leupeptin (5 g/mL), pepstatin A (7 g/mL) and aprotonin (5 g/mL)] were added to the isolation buffer to prevent protein degradation. Mitochondrial respiration rates were measured as described by Spach et al (1979). The cytosolic fraction was prepared by centrifugation of the postmitochondrial supernatant at 100,000 g for 60 min at 4°C followed by one wash step for 30 min.…”

Effect of Ethanol on Liver Triglycerides and Fatty Acid Composition in the Golden Syrian Hamster

“…The totally liquid ethanol diet for rats causes an increase in the 18:2n-6/20:4n-6 ra tio in liver mitochondrial phospholipids even in rats fed the diet containing no etha nol [10,11]. This diet contains 52% of its calories as glucose [29] which, by itself, in hibits delta-6 desaturation of 18:2n-6 [30].…”

“…The study of the effects of ethanol on lipid metabolism is hampered by problems associated with the administration of ethanol to animals. Liquid diets, which are suitable for feeding large amounts of ethanol, cause changes in liver fatty acid composition even when de void of ethanol [10,11]. Rats given ethanol in the drinking water will drink a solution of up to 10% ethanol above which growth is affected.…”

Involvement of the mitochondrial permeability transition pore in chronic ethanol-mediated liver injury in mice

“…Liver mitochondria were isolated by differential centrifugation techniques (71). Briefly, liver was homogenized in a buffer containing 250 mM sucrose, 5 mM HEPES, 3 mM MgCl 2, and 1 mM EGTA (pH 7.4).…”