Ethanol metabolism by the rat pancreas

Synthesis of fatty acid ethyl esters in mammalian tissues after ethanol exposure: a systematic review of the literature

The ability to undergo non-oxidative metabolism from ethanol to fatty acid ethyl esters (FAEEs) varies greatly among tissues and organs. To gain a greater understanding of non-oxidative ethanol metabolism to FAEE, we aimed to collect all published data on FAEE synthesis in mammalian organs and tissues to identify all tissues, organs, and enzymes that are known to, or likely possess FAEE-synthetic activity. A systematic search for relevant papers was performed and two independent reviewers examined potentially relevant abstracts (articles on FAEEs that pertain to ethanol exposure) to determine whether they met the inclusion criteria. Information on FAEE synthesis was retrieved from papers meeting the inclusion/exclusion criteria and summarized by organ/tissue/matrix examined. The systematic search through four databases yielded 78 articles that investigated FAEE synthesis by tissues, tissue fractions and cell lines, and 29 articles that attempted to purify and/or characterize the enzymes involved in FAEE synthesis. Two enzyme activities have been studied: FAEE synthase (FAEES, which conjugates ethanol and free fatty acid) and acyl-CoA: ethanol O-acyltransferase (AEAT, which conjugates ethanol and fatty acyl-CoA). Both activities are expressed by a variety of different enzymes. FAEES activity is the most widely studied and has been purified from several tissues and shown to be associated with several well-known enzymes, while the identity of enzymes possessing AEAT activity remains unknown. The organs and tissues that have been shown to synthesize FAEEs are discussed, with special emphasis on the studies that attempted to elucidate the enzymology of FAEE synthesis in those tissues.

Preventive role of gallic acid on alcohol dependent and cysteine protease-mediated pancreas injury

In order to investigate an association between alcohol consumption and lysosomal cysteine protease induced pancreatic injury and preventive effect of gallic acid as dose-dependent, we determined myeloperoxidase and malondialdehyde levels, serum amylase activities and cathepsin B and L activities in the cytosolic and lysosomal fractions of pancreatic tissue in the ethanol (8 g/kg) and ethanol plus gallic acid (at different doses 50, 100 and 200 mg/kg) given rats. Absolute ethanol (8 g/kg) was given by oral gavage. Gallic acid was dissolved in the saline (2 ml/kg) and administered before 30 min the oral administration of ethanol. Pancreatic myeloperoxidase and also malondialdehyde levels and serum amylase activities were measured. Besides, histological investigations were made. Cathepsin B activities in the cytosolic fraction were decreased by gallic acid (200 mg/kg) and increased in ethanol given rats. Cytosolic/lysosomal ratio of cathepsin B and L were found to be low in the all doses of gallic acid as compared to ethanol group. Serum amylase, pancreatic myeloperoxidase activities and malondialdehyde levels in the ethanol group were higher than in the control group. These were not statistically significant for myeloperoxidase and malondialdehyde. Also, our histopathologic results indicated that ethanol administration increased pancreatic tissue injury. Gallic acid especially at 200 mg/kg improved ethanol-mediated pancreatic tissue damage.In conclusion, gallic acid treatments were decreased release of lysosomal cathepsin B and L enzymes into cytoplasmic fraction and prevented alcohol mediated pancreatic tissue injury. Preventive effect of gallic acid might be dose-dependent.

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) in the cancer diseases

Epidemiological data have identified chronic alcohol consumption as a significant risk factor for cancer in humans. The exact mechanism of ethanol-associated carcinogenesis has remained unknown. The metabolism of ethanol leads to generation of acetaldehyde (AA), which is highly toxic and carcinogenic. The amount of acetaldehyde to which cells or tissues are exposed after alcohol ingestion may be of great importance and may, among others, affects carcinogenesis. Ethanol is metabolized to acetaldehyde by alcohol dehydrogenase (ADH). The enzyme responsible for oxidation of acetaldehyde is aldehyde dehydrogenase (ALDH). Both formation and degradation of acetaldehyde depends on the activity of these enzymes. The total alcohol dehydrogenase activity is significantly higher in cancer tissues than in this healthy organs (e.g. liver, stomach, esophagus, colorectum). Moreover the activity of ADH is much higher than the activity of ALDH. This suggests that cancer cells have a greater capability for ethanol oxidation but less ability to remove acetaldehyde than normal tissues. In addition significant differences of ADH isoenzymes activities between cancer tissues and healthy organs may be a factor intensifying carcinogenesis by the increased ability to acetaldehyde formation from ethanol and disorders in metabolism of some biologically important substances (e.g. retinoic acid). The changes in activity of particular ADH isoenzymes in the sera of patients with different cancers, seem to be caused by release of these isoenzymes from cancer cells, and may be useful for diagnostics of this cancer. The particular isoenzymes of ADH present in the serum may indicate the cancer localization.

The activity of class I, II, III, and IV of alcohol dehydrogenase isoenzymes and aldehyde dehydrogenase in pancreatic cancer

OBJECTIVES

The pancreas can metabolize ethanol via oxidative pathway involving the enzymes alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) as well as the nonoxidative pathway. In this study, we compared the activity of ADH isoenzymes and ALDH in the pancreatic cancer with the activity in normal tissue. In addition, the differences between enzyme activities of drinkers and nondrinkers were compared.

METHODS

For the measurement of the activity of class I and II ADH isoenzymes and ALDH activity, we used the fluorometric methods. The total ADH activity and activity of class III and IV isoenzymes were measured by the photometric method. The samples were taken from 56 pancreatic cancer patients (22 drinkers and 34 nondrinkers) and 56 healthy subjects.

RESULTS

The activity of class III ADH was significantly higher in cancer than in healthy tissues. Total activities of ADH and ALDH were not significantly different in cancer and normal cells. The differences between enzymes of drinkers and nondrinkers in both cancer and healthy tissue were not significant.

CONCLUSION

Pancreatic cancer tissue exhibits higher activity of class III ADH isoenzyme than healthy tissue, and we consider that oxidative pathway of ethanol metabolism via ADH and ALDH does not play a role in pancreatic carcinogenesis.

Ethanol induces secretion of oxidized proteins by pancreatic acinar cells

The pancreas is vulnerable to ethanol toxicity, but the pathogenesis of alcoholic pancreatitis is not fully defined. The intracellular oxidative balance and the characteristics of the secretion of isolated rat pancreatic acinar cells stimulated with the cholecystokinin analogue cerulein were assayed after acute oral ethanol (4 g/kg) load. Pancreatic acinar cells from ethanol-treated rats showed a significant (p < 0.02) lower content of total glutathione and protein sulfhydryls, and higher levels of oxidized glutathione (p < 0.03), malondialdehyde, and protein carbonyls (p < 0.05). Ethanol-intoxicated acinar cells showed a lower baseline amylase output compared to controls, with the difference being significantly exacerbated by cerulein stimulation. After cerulein, the release of protein carbonyls by ethanol-treated cells was significantly increased, whereas that of protein sulfhydryls was significantly decreased. In conclusion, ethanol oxidatively damages pancreatic acinar cells; cerulein stimulation is followed by a lower output of amylase and by a higher release of oxidized proteins by pancreatic acinar cells from ethanol-treated rats. These findings may account for the decreased exocrine function, intraductular plug formation, and protein precipitation in alcoholic pancreatitis.

Alcoholic pancreatitis: new insights into an old disease

Alcoholic pancreatitis is an old disease that continues to present controversial issues. One of the most hotly debated issues is whether alcoholic pancreatitis is a chronic disease from the beginning or if instead it becomes chronic after repeated episodes of acute pancreatitis. Histologic studies, including very large series of patients with alcoholic pancreatitis, have clearly shown that this disease is chronic from the beginning and that, if acute necrotic pancreatitis occurs, it is associated with chronic lesions. The possibility that acute alcoholic pancreatitis can occur in the absence of chronic lesions cannot be excluded, but, if this occurs, it is rare. In addition to alcohol, genetic factors certainly play a determining role. Until now many genetic studies have been made on chronic pancreatitis; the first dealt with hereditary pancreatitis. In this disease it has been shown that mutations of the cationic trypsinogen gene and of SPINK1 are implicated in its pathogenesis. Concerning alcoholic pancreatitis, several studies have been made, but the results so far are disappointing.

Pathogenesis of chronic pancreatitis: an evidence-based review of past theories and recent developments

In the past several decades, four prominent theories of chronic pancreatitis pathogenesis have emerged: the toxic-metabolic theory, the oxidative stress hypothesis, the stone and duct obstruction theory, and the necrosis-fibrosis hypothesis. Although these traditional theories are formulated based on compelling scientific observations, substantial contradictory data also exist for each. Furthermore, the basic premises of some of these theories are directly contradictory. Because of the recent scientific progress in the underlying genetic, cellular, and molecular pathophysiology, there have been substantial advances in the understanding of chronic pancreatitis pathogenesis. This paper will provide an evidence-based review and critique of the traditional pathogenic theories, followed by a discussion of the new advances in pancreatic fibrogenesis. Moreover, we will discuss plausible pathogenic sequences applied to each of the known etiologies.

Role of alcohol metabolism in alcoholic pancreatitis

Metabolism of ethanol by acinar and other pancreatic cells and the consequent generation of toxic metabolites are postulated to play an important role in the development of alcohol-related acute and chronic pancreatic injury. Studies using cultured pancreatic acinar cells and isolated pancreatic acini have established that (i) the pancreas can metabolize ethanol via the oxidative pathway involving the enzymes alcohol dehydrogenase (ADH) and possibly cytochrome P4502E1 (although the role of the latter remains to be fully delineated) as well as the nonoxidative pathway [involving fatty acid ethyl ester (FAEE) synthases] and (ii) the oxidative pathway (which generates acetaldehyde) is quantitatively greater than the nonoxidative pathway, which yields FAEEs. Most recently, pancreatic stellate cells (PSCs) (implicated in pancreatic fibrogenesis) have been reported to exhibit ADH activity, suggesting that the capacity of the pancreas to metabolize ethanol may reside not only in parenchymal (acinar) cells but also in nonparenchymal cells. Polymorphisms/mutations of ethanol metabolizing enzymes have been examined to determine whether they may confer individual susceptibility to alcoholic pancreatitis. However, no association has been demonstrated between ADH and CYP2E1 polymorphisms and the predisposition to alcoholic pancreatitis. Other candidate factors that remain to be studied include polymorphisms of FAEE synthetic enzymes and proteins relevant to antioxidant pathways in the cell. Injury to the pancreas due to its capacity to metabolize ethanol may be mediated by direct effects of both acetaldehyde and FAEEs and by alterations induced within the cells during ethanol metabolism, such as changes in the intracellular redox state and the generation of oxidant stress.

Alcoholic pancreatitis in rats: injury from nonoxidative metabolites of ethanol

The mechanism by which alcohol injures the pancreas remains unknown. Recent investigations suggest a role for fatty acid ethyl ester (FAEE), a nonoxidative metabolite of ethanol, in the pathogenesis of alcohol pancreatitis. In this study, we characterized ethanol-induced injury in rats and evaluated the contribution of oxidative and nonoxidative ethanol metabolites in this form of acute pancreatitis. Pancreatic injury in rats was assessed by edema, intrapancreatic trypsinogen activation, and microscopy after infusing ethanol with or without inhibitors of oxidative ethanol metabolism. Plasma and tissue levels of FAEE and ethanol were measured and correlated with pancreatic injury. Ethanol infusion generated plasma and tissue FAEE and, in a dose-dependent fashion, induced a pancreas-specific injury consisting of edema, trypsinogen activation, and formation of vacuoles in the pancreatic acini. Inhibition of the oxidation of ethanol significantly increased both FAEE concentration in plasma and pancreas and worsened the pancreatitis-like injury. This study provides direct evidence that ethanol, through its nonoxidative metabolic pathway, can produce pancreas-specific toxicity in vivo and suggests that FAEE are responsible for the development of early pancreatic cell damage in acute alcohol-induced pancreatitis.

Ethanol metabolism and transcription factor activation in pancreatic acinar cells in rats

BACKGROUND & AIMS

Ethanol metabolism by pancreatic acinar cells and the role of its metabolites in ethanol toxicity to the pancreas remain largely unknown. Here, we characterize ethanol metabolism in pancreatic acinar cells and determine the effects of ethanol metabolites on nuclear factor kappa B (NF-kappa B) and activator protein (AP)-1, transcription factors that are activated in pancreatitis and mediate expression of inflammatory molecules critical for this disease.

METHODS

We measured activities of fatty acid ethyl ester (FAEE) synthase and alcohol dehydrogenase (ADH), as well as accumulation of ethanol metabolites. We measured the effects of ethanol and its metabolites on NF-kappa B and AP-1 activation by using a gel shift assay.

RESULTS

Pancreas metabolizes ethanol via both oxidative and nonoxidative pathways. Acinar cells are the main source of ethanol metabolism in the pancreas. Compared with the liver, FAEE synthase activity in the pancreas is greater, whereas that of ADH is much less. FAEEs activated NF-kappa B and AP-1, whereas acetaldehyde inhibited NF-kappa B activation. Ethanol decreased NF-kappa B binding activity in acinar cells, which was potentiated by cyanamide.

CONCLUSION

Oxidative and nonoxidative ethanol metabolites regulate transcription factors differently in pancreatic acinar cells. Ethanol may regulate NF-kappa B and AP-1 positively or negatively, depending on which metabolic pathway's effect predominates. These regulatory mechanisms may play a role in ethanol toxicity to the pancreas.

Linkage of oxidative and nonoxidative ethanol metabolism in the pancreas and toxicity of nonoxidative ethanol metabolites for pancreatic acinar cells

BACKGROUND

Alcohol abuse is a major cause of pancreatic damage. Recent experimental evidence suggests that fatty acid ethyl esters (FAEE), nonoxidative ethanol metabolites, injure pancreatic acinar cells. Linkage between oxidative and nonoxidative metabolism of ethanol in the pancreas may contribute to increased FAEE levels.

METHODS

To study the association between oxidative and nonoxidative ethanol metabolism, FAEE concentration and FAEE synthase activity in rat pancreatic and liver homogenates incubated with ethanol were evaluated with and without inhibitors of oxidative ethanol metabolism. For toxicity studies, trypsinogen activation peptide synthesis as a measure of pancreatic cell injury was quantitated in unstimulated and cerulein-stimulated isolated pancreatic acinar cells incubated with ethanol or FAEE.

RESULTS

Inhibition of oxidative ethanol metabolism results in a 2- to 3-fold increase in nonoxidative ethanol metabolism to FAEE in pancreas and in liver. Both ethanol and FAEE induce increased intracellular trypsinogen activation by more than 50% in the presence of physiologic concentrations of cerulein in vitro.

CONCLUSIONS

These findings demonstrate that the inhibition of oxidative ethanol metabolism results in an increase in flux through the nonoxidative pathway and support the proposition that alcohol-induced pancreatic injury is mediated at least in part by FAEE, which are important products of pancreatic ethanol metabolism.

A review: acute and chronic effects of ethanol and alcoholic beverages on the pancreatic exocrine secretion in vivo and in vitro

Whereas oral or intraduodenal ethanol causes a moderate stimulation of pancreatic bicarbonate and enzyme output, intravenous ethanol inhibits basal and hormonally stimulated pancreatic exocrine secretion in humans, dogs, cats, pigs, rabbits, and rats. This inhibition could be mediated by inhibitory cholinergic mechanisms or be the result of a direct cellular effect of ethanol. In vitro investigations have specified several signaling molecules that may be involved in the action of ethanol on stimulus-secretion coupling in the exocrine pancreas, including cyclic adenosine monophosphate, intracellular calcium, and cholecystokinin and somatostatin receptors. In difference to pure ethanol solutions and distilled spirits, beer strongly stimulates pancreatic enzyme output, probably by nonalcoholic fermentation products. During chronic alcoholism, the ethanol-induced inhibition is replaced by an enhanced enzyme output that causes intraductal protein precipitation. In vitro investigations suggest that this increase is reversible after alcohol withdrawal. The occurrence of protein precipitates is considered to be a crucial step in the development of chronic alcoholic pancreatitis in humans. Other ethanol-induced secretory alterations that may contribute to the development of alcoholic pancreatitis are a decreased secretion of trypsin inhibitor, an increased cholinergic tone, and changes in the concentration of lithostathine.

Metabolism of ethanol by rat pancreatic acinar cells

It has been postulated that ethanol-induced pancreatic injury may be mediated by the oxidation of ethanol within the pancreas with secondary toxic metabolic changes, but there is little evidence of pancreatic ethanol oxidation. The aims of this study were to determine whether pancreatic acinar cells metabolize significant amounts of ethanol and, if so, to compare their rate of ethanol oxidation to that of hepatocytes. Cultured rat pancreatic acinar cells and hepatocytes were incubated with 5 to 50 mmol/L carbon 14-labeled ethanol (25 dpm/nmol). Ethanol oxidation was calculated from the production of 14C-labeled acetate that was isolated by Dowex ion-exchange chromatography. Ethanol oxidation by pancreatic acinar cells was demonstrable at all ethanol concentrations tested. At an intoxicating ethanol concentration (50 mmol/L), 14C-labeled acetate production (227+/-20 nmol/10(6) cells/h) approached that of hepatocytes (337+/-61 nmol/10(6) cells/h). Phenanthroline (an inhibitor of classes I through III isoenzymes of alcohol dehydrogenase (ADH)) inhibited pancreatic ethanol oxidation by 90%, but 4-methylpyrazole (a class I and II ADH inhibitor), carbon monoxide (a cytochrome P450 inhibitor), and sodium azide (a catalase inhibitor) had no effect. This study has shown that pancreatic acinar cells oxidize significant amounts of ethanol. At intoxicating concentrations of ethanol, pancreatic acinar cell ethanol oxidation may have the potential to contribute to pancreatic cellular injury. The mechanism appears to involve the class III isoenzyme of ADH.

Alcohol and the pancreas

Alcoholic pancreatitis is a major, often lethal complication of alcohol abuse. Until recently it was generally accepted that alcoholic pancreatitis was a chronic disease from the outset. However, there is now emerging evidence in favour of the necrosis-fibrosis hypothesis that alcoholic pancreatitis begins as an acute process and that repeated acute attacks lead to chronic pancreatitis, resulting in exocrine and endocrine failure. Over the past 10-15 years, the focus of research into the pathogenesis of alcoholic pancreatitis has shifted from possible sphincteric and ductular abnormalities to the acinar cell itself which has increasingly been implicated as the initial site of injury. Recent studies have shown that the acinar cell can metabolize alcohol at rates comparable to those observed in hepatocytes. In addition, it has been demonstrated that alcohol and its metabolites exert direct effects on the pancreatic acinar cell which may promote premature digestive enzyme activation and oxidant stress. The challenge remains to identify predisposing and triggering factors in this disease.

Inhibition of bacteriocolonic pathway for ethanol oxidation by ciprofloxacin in rats

Many colonic bacteria possess marked alcohol dehydrogenase (ADH) activity and are capable of oxidizing ethanol to acetaldehyde both in vitro and in vivo. We have recently shown that part of ingested ethanol is metabolized to acetaldehyde in the colon during normal alcohol metabolism. To assess the contribution of this bacteriocolonic pathway for ethanol oxidation to total ethanol metabolism, the elimination rate of ethanol, faecal aerobic flora and faecal ADH activity were determined in rats before and after the treatment with ciprofloxacin (200 mg/kg/day) for four days. Ciprofloxacin treatment decreased ethanol elimination rate from 310+/-9 to 282+/-13 mg/kg/h (mean+/-SE; p<0.02), markedly reduced faecal aerobic flora, and also lowered faecal ADH activity from 63+/-17 to 17+/-7 nmol/min/mg faeces (p<0.05). Neither hepatic ADH nor microsomal ethanol oxidizing system activities were affected by the ciprofloxacin treatment. On the contrary, an acute intraperitoneal dose of ciprofloxacin had no effect on the rate of ethanol elimination. These results support the significant role of the bacteriocolonic pathway in total ethanol elimination, and open a new, microbiological, perspective for studies on ethanol metabolism and pathogenesis of alcohol related organ damages.

The influence of acute ethanol ingestion on phospholipase D activity in rat pancreas. An in vitro and in vivo study

CONCLUSION

Since phosphatidic acid (PA), a product of phospholipase D(PLD), is known as a second messenger probably involved in cell proliferation and differentiation, our results potentially suggest a new mechanism for pancreatic tissue injury after ethanol ingestion.

BACKGROUND

The mechanisms by which ethanol causes pancreatic injury are still not clear. In vitro studies have suggested a relationship of PLD to ethanol metabolism. This study was undertaken to establish the involvement of PLD in ethanol metabolism in isolated pancreatic acini and to determine the influence of acute ethanol ingestion on PLD activity in pancreas and pancreatic growth after cerulein (Ce) infusion.

METHODS

Dispersed pancreatic acini prelabeled with 3H myristic acid were incubated with 500 pM Ce in the presence of different concentrations of ethanol; then labeled PA and phosphatidylethanol (PEt) production were measured under the same experimental conditions. For in vivo study, male rats were infused with Ce (0.25 microgram/kg/h) or saline; 1 h before infusion, animals were treated with 40% ethanol (5 g/kg p.o.) or saline, respectively. After 1, 2, and 48 h of Ce infusion, rats were killed; dispersed pancreatic acini were then prepared and PLD activity was measured. Pancreatic weight, protein, RNA, and DNA content were also established.

RESULTS

The production of PEt in vitro after Ce stimulation was significantly elevated with 1% ethanol in the medium. In the presence of different concentrations of ethanol (0.5-2%), a significant inhibition of PA accumulation in in vitro experiments was observed. The decrease of PA accumulation with ethanol was parallel to the increase of PEt production under the same experimental conditions. PLD activity was significantly elevated after 1 and 2 h of Ce infusion (116 and 105%, respectively), reaching control value after 48 h. Acute ethanol ingestion significantly diminished PLD activity after 1 and 2 h. After 48 h of Ce infusion, a significant increase in pancreatic weight, protein, RNA, and DNA content in pancreatic tissue was found. Ethanol was not able to influence pancreatic weight, proteins and RNA content. However, it had the potency to diminish DNA content after 48 h of Ce infusion.

Acute ethanol administration induces oxidative changes in rat pancreatic tissue

BACKGROUND

There is mounting clinical evidence that ethanol toxicity to the pancreas is linked with glutathione depletion from oxidative stress but there is not experimental proof that this occurs.

AIMS AND METHODS

The effect of acute ethanol ingestion (4 g/kg) on the pancreatic content of reduced (GSH) and oxidised (GSSG) glutathione, malondialdehyde (MDA), and carbonyl proteins were therefore studied in the rat.

RESULTS

Ethanol caused a significant reduction in GSH (p < 0.02) and an increase in GSSG (p < 0.005), MDA (p < 0.05), and carbonyl proteins (p < 0.05) in the rat pancreas. The GSH/GSSG ratios were significantly decreased after ethanol, especially in rats pretreated with diethylmaleate (DEM), a GSH blocker. Administration of ethanol after DEM further increased the rate of lipid and protein oxidation. Pretreatment with cyanamide (an inhibitor of aldehyde dehydrogenase) but not with 4-methylpyrazole (an alcohol dehydrogenase inhibitor) caused higher production of GSSG and MDA.

CONCLUSIONS

These findings indicate that acute ethanol reduces the pancreatic content of GSH, which seems to be protective against ethanol toxicity, since its depletion is accompanied by increased oxidative damage to cell structures. The further increase of lipid peroxidation and GSSG production in the presence of cyanamide suggests that acetaldehyde might be responsible for the oxidative changes that occur in pancreatic cells after ethanol administration.

Ethanol-induced modification of somatostatin-responsive adenylyl cyclase in rat exocrine pancreas

Male rats were given 10% (w/v) ethanol in drinking fluid during the first week, 15% (w/v) during the second week, 20% (w/v) during the third, and 25% (w/v) during the fourth week, at the end of which they were kept on 25% (w/v) ethanol drinking water for 3 weeks. Some animals were then allowed the withdrawal of ethanol for a period of 2 weeks or 7 weeks. No significant differences were seen for the basal and forskolin (FK)-stimulated adenylate cyclase (AC) enzyme activities in the pancreatic acinar membranes of ethanol-treated and ethanol withdrawal rats as compared to the control group. Chronic ethanol ingestion resulted in an attenuation of somatostatin(SS)-inhibited FK-stimulated AC in rat pancreatic acinar membranes. The ability of the stable GTP analogue 5'-guanylylimidodiphosphate (Gpp[NH]p) to inhibit FK-stimulated AC activity was also decreased in pancreatic acinar membranes from ethanol-treated rats. Gpp[NH]p was a much less potent inhibitor of SS binding in the pancreatic acinar membranes from chronic ethanol-treated animals than in those from controls, suggesting a change of Gi. A significant reduction in the number of 125I-Tyr11-SS receptors was observed after ethanol ingestion, when compared with control values. Two weeks after the replacement of the ethanol solution by water, the ethanol effect on the parameters cited above persisted. At week 7 of withdrawal, these parameters reached the level of water controls. Ethanol administration did not affect either the number or the affinity of secretin receptors as compared to control values which suggests that the change in SS binding is not a non-specific effect. Neither chronic ethanol consumption nor withdrawal affected somatostatin-like immunoreactivity (SSLI). These results suggest that the attenuated inhibition of AC by SS in pancreatic acinar membranes from ethanol-treated rats and ethanol withdrawal (2 weeks) rats may be caused by decreases in both Gi activity and in the number of SS receptors. Alternatively, an uncoupling of SS receptors from Gi and/or a decrease in the level of functional Gi may result in both a decrease in apparent Bmax for SS binding and in SS-mediated inhibition of AC. Since SS has been suggested to be an inhibitor of basal and cholecystokinin (CCK)- and/or secretin-stimulated exocrine pancreatic secretion, it is tempting to speculate that the impairment of the SS receptor/effector system seen in the present study can participate in the increase of basal pancreatic exocrine secretion described after chronic ethanol consumption.

Acute effects of ethanol and ethanol plus furosemide on pancreatic capillary blood flow in rats

The effects of intravenous ethanol and ethanol plus furosemide on pancreatic capillary blood flow (PCBF) were investigated using a laser-Doppler flowmeter. Forty Sprague-Dawley male rats were divided into 4 groups: (1) control, (2) 80% ethanol, (3) 80% ethanol plus furosemide, and (4) furosemide. Mean arterial blood pressure and heart rate were monitored. Levels of serum amylase, calcium, electrolytes, ethanol, and furosemide (groups 3 and 4) were measured, and samples of pancreatic tissue were obtained. The ethanol and furosemide levels were statistically different (p < 0.05). PCBF significantly decreased (p < 0.05) in group 2, increased (p < 0.05) in group 3, and did not differ (p > 0.05) between groups 1 and 4. Histopathologic analysis revealed swollen acini in group 2 and sparse focal necrosis without acinar swelling in group 3. The depressant effect of ethanol on PCBF may be the result of its direct action on pancreatic cells causing edema and capillary compression rather than on primary vascular control mechanisms that adjust blood flow. Furosemide counters this effect.

Nonoxidative metabolism of ethanol in the pancreas; implication in alcoholic pancreatic damage

Alcohol dehydrogenase activity and fatty acid ethyl ester synthase activity were measured in various organs of male Wistar strain rats. The mean (+/- SE) values of alcohol dehydrogenase activity in liver, testis, pancreas and brain were 223 +/- 34, 35 +/- 13, 27 +/- 17 and 24 +/- 15 nmol/hr/mg protein, respectively, but not detectable in heart and skeletal muscle. Fatty acid ethyl ester synthase activity in pancreas, liver, testis and heart were 1348 +/- 263, 23 +/- 14, 17 +/- 3 and 2 +/- 1 nmol/hr/mg protein, respectively, but not detectable in brain and skeletal muscle. Alcohol dehydrogenase activity, fatty acid ethyl ester synthase activity, fatty acid ethyl ester content and amylase activity were measured in pancreas of rat after 7 weeks of ethanol feeding. Compared with control rats, ethanol-fed rats had normal fatty acid ethyl ester synthase activity and alcohol dehydrogenase activity. However, fatty acid ethyl ester content increased five-fold and amylase activity decreased up to 20% of the control group. Fatty acid ethyl ester content was inversely correlated with amylase activity. These results suggest that fatty acid ethyl ester may be responsible for the development of pancreatic damage by ethanol.

Effect of alcohol and alcoholic beverages on meal-stimulated pancreatic secretion in humans

Alcohol and alcoholic beverages may have different effects on pancreatic secretion and hormone release in humans. To test this hypothesis we studied the effects of an alcohol solution and a glucose solution and compared them with those of alcoholic beverages on postprandial pancreatic secretion and release of gastrin, trypsin, and cholecystokinin in 6 healthy nonalcoholic male volunteers. Pancreatic enzyme secretion was measured in duodenal aspirate, plasma trypsin, and gastrin by radioimmunoassay and cholecystokinin by bioassay. The meal plus glucose significantly stimulated pancreatic enzyme secretion, release of gastrin and cholecystokinin, and caused no changes in plasma trypsin. The alcohol solution and all beverages added to the meal caused similar increases in alcohol blood levels and significantly less pancreatic enzyme secretion compared with the meal plus glucose. Plasma trypsin levels remained unchanged. Compared with the meal plus glucose, wine and beer caused a significantly higher release of gastrin, and beer also released significantly more cholecystokinin. Inhibition of pancreatic enzyme secretion stimulated by a meal in nonalcoholics is a common effect of alcohol and alcoholic beverages despite some differences on release of gastrointestinal peptides. This effect may have some implications in the pathogenesis of alcoholic pancreatitis.

Alcohol-induced pancreatic injury (Part 2). Evolution of pathogenetic theories

In Part I of this paper, features of alcoholic pancreatitis that are still poorly understood were reviewed and factors that might favor biliary-pancreatic reflux were summarized. Part II deals with additional pathogenetic schemes that might shed light on this perplexing disorder.

Effect of chronic ethanol ingestion on pancreatic protein synthesis

The effect of chronic ethanol feeding on pancreatic protein synthesis was assessed by studying the rate of incorporation of [3H]leucine into proteins in isolated rat pancreatic acini in vitro. Chronic ethanol feeding increased the rate of protein synthesis (2-3-fold) compared to controls fed an isocaloric diet. The onset of the increase in protein synthesis was detectable 2 days after the beginning of ethanol feeding, reached a maximum after 7 days and remained constant for up to 4 months. The increased incorporation of [3H]leucine was not due to an increased turnover of proteins as measured in pulse-chase experiments. After separation of individual digestive enzymes by SDS-polyacrylamide gel electrophoresis and determination of the distribution of radioactivity in different proteins, a general increase in the rate of incorporation of the label into all of the proteins was observed. In contrast to the observations made with isolated acini, there was no significant difference between the control and ethanol-fed groups when the rate of pancreatic protein synthesis was measured in vivo. However, overnight withdrawal of ethanol led to an increase of approx. 70% in protein synthesis in the ethanol-fed group. These results suggest that chronic ethanol ingestion modifies the control of pancreatic protein synthesis; the enhanced protein synthesis is expressed in isolated acini, i.e., in the absence of physiological factors present during chronic ethanol ingestion and in vivo after ethanol withdrawal.

Ethanol-induced alterations in exocrine pancreatic amino acid transport and secretion

The effects of ethanol on exocrine pancreatic amino acid transport and secretion were investigated during perfusion of the isolated rat pancreas with ethanol concentrations ranging from 0.06% to 4.1%. Amino acid transport was quantitated using a rapid dual isotope dilution technique in which unidirectional substrate uptake (15-20 sec) is assessed relative to an extracellular tracer. Pancreatic secretion evoked by 0.3 microM carbachol was abolished during perfusion with 0.32% ethanol. Influx of L-lysine, L-serine and methylaminoisobutyric acid (MeAIB) was marginally increased by 0.32% ethanol but significantly inhibited during subsequent perfusion with 1.28-4.1% ethanol. Pancreatic oxygen consumption and effluent PCO2 levels decreased with increasing ethanol concentration, and the control venous pH (7.21 +/- 0.01, n = 8) gradually approached arterial pH values (7.46 +/- 0.02, n = 9). These results indicate that low concentrations of ethanol readily inhibit secretagogue-induced pancreatic secretion. Amino acid transport at the basolateral membrane of the exocrine pancreatic epithelium appears only to be inhibited after acute exposure to high ethanol concentrations.

Control of alcohol addiction by SKV therapy--its action on water, food intake, brain function and cell membrane composition

Alcohol being easily permeable through cell membrane causes toxic damage to many tissues. Rats drinking aqueous ethanol (25% v/v) for 120 days and 240 days showed an initial rise in body weight. The reduced rate in weight gain in chronic alcoholism is associated with a fall in food intake. Ethanol ingesting animals showed slow response to stimuli and increase in blood ethanol and serum GGTP levels. Liver plasma membrane, kidney brush-border membrane and pancreatic plasma membrane from alcoholic rats showed significant alterations in cholesterol/phospholipid molar ratio and membrane ATPases. Water retention with the enlargement of liver and kidney associated with increased fluid consumption are also seen during alcoholism. SKV by breaking alcohol dependence reduces drinking, lowers blood ethanol level and fluid intake without developing withdrawal symptoms. Restriction of ethanol intake by SKV therapy resulted in the reversal of organ enlargement and membrane composition in alcoholics.

The effect of ethanol on enzyme synthesis and secretion in isolated rat pancreatic lobules

This study investigates the effect of ethanol on enzyme synthesis and secretion in rat pancreatic lobules. Ethanol caused a dose-dependent inhibition of 3H-leucine incorporation into total protein. Examination of the time dependence showed that ethanol inhibited protein synthesis at each time point. Removal of ethanol partially reversed this inhibition. An autoradiograph of the newly synthesized proteins separated on SDS-PAGE showed that ethanol inhibited synthesis of all proteins. 14C-cycloleucine uptake was not altered by ethanol, excluding inhibition of amino acid uptake as the mechanism for the decreased protein synthesis induced by ethanol. Electron microscopy revealed no ultrastructural damage. Ethanol had no effect on the stimulated release of (i) amylase from zymogen granules nor (ii) newly synthesized pulse labelled enzymes. Acetaldehyde had no inhibitory effect on enzyme synthesis or secretion indicating that ethanol per se and not its metabolite is inhibitory. The decreased synthesis after acute exposure to ethanol with preservation of exocytosis would limit the autodigestive potential of pancreatic tissue. This may explain why isolated toxic doses of ethanol are rarely if ever associated with pancreatitis.

The effect of chronic ethanol consumption on salivary gland morphology and function in the rat

Chronic ethanol consumption in rats resulted in a striking fat accumulation in the acinar cells of the parotid gland demonstrated by light microscopy. In addition, a significant decrease in parotid wet weight (p greater than 0.02) and in protein content of the gland (p greater than 0.02) was observed following alcohol feeding. Wet weight, protein content, and morphology of the submaxillar gland were not affected by ethanol feeding. Alcohol metabolism, similar to that found in the pancreas, via a cytosolic alcohol dehydrogenase could be demonstrated in both the parotid and the submaxillar gland. However, the activity of this enzyme was not affected by chronic ethanol ingestion. Subsequently, chronic ethanol consumption significantly decreased salivary flow rate stimulated by pilocarpine hydrochloride (p greater than 0.02), salivary alpha-amylase activity (p greater than 0.02), and salivary sodium concentration (p greater than 0.01), whereas potassium concentration of the saliva was increased (p greater than 0.05). In contrast salivary total protein concentration was not affected by alcohol ingestion. The changes of salivary electrolyte composition observed after chronic ethanol feeding could be due to an altered aldosterone metabolism or to a change in aldosterone receptors of the parotid gland caused by ethanol administration. The reduced salivary flow could play a role in the pathogenesis of oropharyngeal cancer in the alcoholic.

Endogenous ethanol--its metabolic, behavioral and biomedical significance

Ethanol is constantly formed endogenously from acetaldehyde, and level of the former can be measured in both human beings and animals. Acetaldehyde can be generated in situ from the metabolism of pyruvate, threonine, deoxyribose-5-phosphate, phosphoethanolamine, alanine and presumably from other substrates. The levels of blood and tissue endogenous ethanol change as a function of various physiologic and experimental conditions such as starvation, aging, stress, cooling, adrenalectomy, etc. and are regulated by many exogenous compounds such as antimetabolites, derivatives of amino acids, lithium salts, disulfiram, cyanamide, etc. Under free choice alcohol selection situations, the levels of endogenous ethanol in rat blood and alcohol preference by the animals are negatively correlated. Similar negative correlations have been found between the levels of blood endogenous ethanol and the frequency of delirium in alcoholic patients undergoing alcohol withdrawal. Endogenous ethanol and acetaldehyde can therefore be regarded as compounds which fulfil substrate, regulatory and modulator functions.

Acetaldehyde inhibition of protein synthesis in isolated rat pancreatic acini

Exposure of isolated dispersed pancreatic acini to increasing concentrations of ethanol (5 to 500 mM) or acetaldehyde (0.5 to 100 mM) produced a progressive inhibition of [3H]leucine incorporation into both "cellular" (those remaining in the cell) and "secretory" (those released into the medium) proteins. Whereas 500 mM ethanol caused 90-95% inhibition in the synthesis of "cellular" and "secretory" proteins, the concentration of acetaldehyde needed to produce a similar inhibition was found to be 50 mM. All subsequent experiments were performed with 12.5 mM acetaldehyde, a concentration that consistently inhibited acinar protein synthesis by about 50%. The acetaldehyde-mediated inhibition of acinar protein synthesis was partially normalized when this metabolite was removed after 30 min during a 90-min incubation period. In the presence of acetaldehyde, the secretion of 3H-pulse-labeled proteins, but not amylase, trypsinogen, or chymotrypsinogen, was greatly depressed. Acetaldehyde also caused a marked reduction in [3H]uridine incorporation into acinar RNA. The entry of [3H]uridine, [3H]leucine, and [3H]aminoisobutyric acid into isolated acini was found to be slightly (15-25%) decreased by acetaldehyde. It is concluded that acetaldehyde exerts a direct toxic effect on isolated dispersed pancreatic acini as evidenced by diminution of both protein and RNA synthesis and decreased secretion of the newly synthesized proteins. This inhibitory effect of acetaldehyde could be partially reversed.

Irreversible inhibition by acetaldehyde of cholecystokinin-induced amylase secretion from isolated rat pancreatic acini

Acetaldehyde inhibited both amylase secretion induced by maximal concentrations (300 pM) of cholecystokinin octapeptide and the binding of radioiodinated cholecystokinin to receptors on isolated rat pancreatic acini. This inhibition was concentration dependent (10 mM to 1 M for amylase secretion and 100 mM to 1 M for binding). However, a correlation between the two inhibitory effects could not be obtained. Furthermore, the inhibitory effects were not reversible. Acetaldehyde did not alter the basal amylase secretion between 6 and 45 mM concentrations. However, 60, 100 and 300 mM acetaldehyde significantly decreased basal amylase secretion; no significant change in amylase secretion was observed at 600 mM and 1 M. Higher concentrations of acetaldehyde produced a 2- to 10-fold increase in basal amylase secretion. 51Cr release from prelabeled acini revealed no significant cell membrane damage between 10 and 600 mM acetaldehyde. These data suggest that acetaldehyde inhibition of cholecystokinin-induced amylase secretion is intracellularly mediated.

Effect of ethanol on cholecystokinin-induced enzyme secretion from isolated rat pancreatic acini

Cholecystokinin octapeptide (CCK8)-stimulated amylase release in isolated rat pancreatic acini was inhibited over 30% by 600 mM ethanol. The configuration of the dose-response curve for CCK8, however, in the presence of ethanol was similar to that of the control. Amylase release elicited by maximal concentrations of CCK8 (300 pM) was inhibited by increasing concentrations of ethanol (0.3 to 1.3 M), and this inhibition was concentration dependent. In addition, the binding of [125I]CCK33 to specific membrane receptors on acini was inhibited by ethanol in a dose-dependent manner. A positive correlation between the inhibitory effects of ethanol on CCK binding and CCK-induced amylase release was observed. Furthermore, these inhibitory effects of ethanol were reversible. Basal amylase release, however, was increased 20-50% by ethanol between the concentrations of 0.3 and 1.3 M; higher concentrations caused a leakage of amylase from the acini both in the absence and presence of 300 pM CCK8. This is confirmed by 51Cr release from prelabeled acini which revealed no significant damage to acinar cell membrane between 0.3 and 1.6 M ethanol, but significant damage to acini at higher concentrations. These data suggest that the 600 mM ethanol-induced inhibition of CCK action in acini is due to reversible perturbation of the acinar cell membrane.

Decrease in arachidonoyl-containing phosphatidylinositols in pancreas of rats fed an ethanol-containing diet

The composition of the glycerophosphatides in pancreas and liver was studied in rats fed an ethanol-containing diet and in pair-fed controls. The fraction of arachidonoyl-containing phosphatidylinositols in pancreas was much lower in the former rats, also when the rats were starved for a final 24 hr period. This fraction was also lower in fed than in starved control rats. The effect was not observed after acute administration of ethanol. It is suggested that the decrease in arachidonoyl-containing phosphatidylinositols was due to chronic pancreatic hyperfunction in the ethanol-fed rats.

Ethanol and the pancreas

The acute and chronic effects of ethanol on pancreatic structure and function are discussed. Acute necrotizing, acute edematous, acute relapsing, chronic relapsing, and painless pancreatitis have an established association with ethanol abuse. The management of these disorders is outlined.

Pathogenesis of alcoholic pancreatitis

The pathogenesis of alcoholic pancreatitis continues to be a puzzle. Of the many theories as to how alcohol might cause pancreatic damage, none satisfactorily explains why only a minority of alcoholics develop clinical pancreatitis. Hypertriglyceridemia and inherited factors could be important antecedents in some individuals, and high fat and protein diets may favour the development of the disease. Disturbances of the sphincter of Oddi have been postulated, but there are experimental and theoretical objections to the view that alcoholic pancreatitis generally results from sphincter dysfunction (obstruction-hypersecretion, biliary-pancreatic reflux and duodeno-pancreatic reflux). Biochemical studies of the effect of alcohol on pancreatic tissue have so far been relatively unrewarding. The most widely held view is that alcohol causes the deposition of protein in peripheral ducts leading to obstruction, inflammation and degeneration. However, it remains to be shown that these deposits are the cause rather than a result of pancreatic inflammation. Research might be facilitated by the development of a suitable animal model of the disease.