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

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.

Decreased content of arachidonoyl species of phosphatidylinositol phosphates in pancreas of rats fed on an ethanol-containing diet

Phosphatidylinositol (PtdIns), phosphatidylinositol 4-phosphate (PtdIns4P) and phosphatidylinositol 4,5-diphosphate [PtdIns(4,5)P2] were isolated from the pancreas of rats fed an ethanol-containing liquid diet for 24 days and from the corresponding pair-fed controls. The isolation involved chromatography on a lipophilic anion exchanger in the phosphate form. The species composition was determined by fast-atom bombardment mass spectrometry. The compositions of PtdIns4P and PtdIns(4,5)P2 were similar to that of PtdIns, with the stearoyl/arachidonoyl species constituting about 32% of the total, compared with 38% in PtdIns. PtdIns(4,5)P2 contained a larger fraction of fully saturated species than PtdIns. The PtdIns species having an arachidonoyl group were about half as abundant in the ethanol-treated as in the control rats. The differences between ethanol-fed and control rats were qualitatively similar for PtdIns, PtdIns4P and PtdIns(4,5)P2, but were less marked for PtdIns4P and PtdIns(4,5)P2. The results indicate that the species compositions of PtdIns4P and PtdIns(4,5)P2 reflect that of PtdIns, and that the changes of PtdIns4P and PtdIns(4,5)P2 in ethanol-treated rats are secondary to changes in PtdIns.

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.

Influence of dietary fats on pancreatic phospholipids of chronically ethanol-treated rats

Male rats were given liquid diets by pair-feeding for 24-30 days, and phosphatidylinositols in pancreas were analyzed as derivatives of diacylglycerols and fatty acids. Addition of arachidonic acid or changing the fat component (35 energy %) in the liquid diet from olive oil/corn oil to oil from Borago officinalis, which contains 22% gamma-linolenic acid, increased the fraction of arachidonoyl-containing species. This fraction was decreased by more than 50% by substituting ethanol for 36 of the 47 energy% provided by carbohydrate. A smaller difference between ethanol-fed and control rats was seen in the composition of phosphatidylcholines and phosphatidylethanolamines. There was no difference in the composition of phosphatidylinositols when fat, instead of ethanol, was used to substitute the 36 energy % in the diet containing olive oil/corn oil. Substituting ethanol for 28 of 35 energy% provided by fat as corn oil in a liquid diet had no effect on the fraction of arachidonoyl-containing species. The results indicate that the effect of ethanol on phosphatidylinositols in pancreas is not due to a deficiency of arachidonic acid, and that the effect of the ethanol-containing diet is not due to the lowered carbohydrate content. However, high contents of fat or of ethanol appear to be necessary for the effect.

Composition of platelet phosphatidylinositol and phosphatidylcholine after ethanol withdrawal

Platelet phosphatidylinositol and phosphatidylcholine composition, ADP-induced platelet aggregation and associated thromboxane B2 formation were studied in alcoholics after a period of heavy drinking and in healthy non-alcoholic volunteers. The composition of these phospholipids in alcoholics was different from that seen in the control subjects. The most prominent change was a decrease in the relative amount of stearoyl-arachidonoyl species in the phosphatidylinositol fraction. Particularly this species of PI might be involved in the transmission of transmembrane signals. During detoxification changes were also observed in the extent of ADP-induced platelet aggregation and the amount of thromboxane B2 produced. Changes in platelet phospholipid composition might influence platelet reactivity in alcoholics.

Phosphatidylinositol composition in pancreas and submaxillary gland of ethanol-fed rats

The possibility that changes in the stimulus-secretion coupling are involved in the etiology of pancreatitis was investigated by analysis of the molecular composition of the phosphatidylinositols in pancreas of rats fed a liquid ethanol-containing diet and pair-fed controls. The arachidonoyl-containing phosphatidylinositols were about half as abundant in the ethanol-fed rats. Opposite differences were seen for the major species containing linoleoyl, oleoyl or stearoyl groups at C-2. Ethanol-induced lipid peroxidation did not seem to be involved, since carbon tetrachloride administration had no effect on the composition. In the submaxillary gland, that has a similar stimulus-secretion coupling, the arachidonoyl-containing phosphatidylinositols constituted about a 25% smaller fraction in the ethanol-fed rats. Dexamethasone administration did not change the effect. Possibly, decreased secretory response in these glands in ethanol-fed rats is caused by the change in phosphatidylinositol composition.