The Effect of Acute Ethanol Treatment on Lipid-Reesterifying Enzymes of the Rat Small Bowel J.B. Rodgers, MD, and R.J. O'Brien, BA
The acute effects of intraduodenal administration of ethanol, 5 g/kg body weight, on intestinal activities of lipid-reesterifying and disaccharidase enzymes of the small bowel were studied. Results were compared to those produced in controls receiving isocaloric amounts of glucose by the same route. AcyI-CoA:monoglyceride acyltransferase, acyI-CoA synthetase (acid:CoA ligase (AMP) EC 6.2.1.3), sucrase, and lactase assays were performed on jejunal samples; acyI-CoA synthetase assay was performed on ileal samples. Ethanol produced greater activities of the lipid-reesterifying enzymes in the jejunum than did glucose. Ileal specific activity of acyI-CoA synthetase was also increased in the experimental group. No effect of ethanol on jejunal disaccharidase enzyme activities was noted. It is concluded that ethanol given acutely has a specific stimulating effect on intestinal enzymes involved in lipid absorption.
Considerable attention has been focused in recent years on the effects of ethanol on smallbowel structure and function. In humans chronic exposure to alcohol has been shown to inhibit uptake of folio acid by the jejunum (1) and vitamin B12 by the terminal ileum (2). Chronic exposure to this agent in both man and rats has been shown to cause ultrastructural changes in the small bowel (3). Acute studies in man (4) and in rats (5) have demonstrated impaired transport of amino acids by the intestine. More recently, it has been reported that acute ethanol treatment was associated with scattered hemorrhagic lesions in the rat small bowel in association with reduction of lactase activity (6) and that chronic administration produced blunting of jejunal villi plus reduced activities of lactase and alkaline phosphatase (6). In our laboratory, we have been interested in factors that influence the activities of the smallFrom the Department of Medicine, AlbanyMedical College, Albany, New York. Address for reprint requests: Dr. J.B. Rodgers, Department of Medicine, Albany Medical College, Albany, New York 12208. 354
intestinal, lipid-reesterifying enzymes. These are required for normal absorption of fat by the small bowel. Previous studies have indicated that these enzymatic activities are affected by the amount of lipid presented for absorption (79). Certain toxic agents, such as methotrexate, have been shown to decrease these enzyme activities in association with malabsorption of lipid in vivo (10). The current study of acute exposure to ethanol was done to determine whether this agent has any adverse or stimulating effect on these microsomal lipid reesterifying enzyme activities of the rat intestinal mucosa. To determine whether any alteration caused by ethanol was fairly specific for the enzymes involved in lipid absorption or was part of a more general response of the intestine to this agent, sucrase and lactase assays were also done on jejunal samples. These enzymes are digestive in function and are required for absorption of simple carbohydrate molecules. Their location in the mucosal cell, being basically on the brush border, also differs from that of the lipidreesterifying enzymes. It was felt that if similar Digestive Diseases, Vol. 20, No. 4 (April 1975)
EFFECT OF ETHANOL ON RAT LIPID ENZYMES Table 1. Jejunal Lipid Reesterifying Enzyme Activities in Ethanol-Treated and Glucose-Treated Rats MG-Acyltrans Microsomal protein (rag)*
Specific activity*l-
15.9i2.2
119i18
Ethanol-treated rats (N=7) Glucose-treated rats (N=7) P
16.0• NS
79•
The acute effects of intraduodenal administration of ethanol, 5 g/kg body weight, on intestinal activities of lipid-reesterifying and disaccharidase enzymes of the small bowel were studied. Results were compared to those produced in controls receiving isocaloric amounts of glucose by the same route. AcyI-CoA:monoglyceride acyltransferase, acyI-CoA synthetase (acid:CoA ligase (AMP) EC 6.2.1.3), sucrase, and lactase assays were performed on jejunal samples; acyI-CoA synthetase assay was performed on ileal samples. Ethanol produced greater activities of the lipid-reesterifying enzymes in the jejunum than did glucose. Ileal specific activity of acyI-CoA synthetase was also increased in the experimental group. No effect of ethanol on jejunal disaccharidase enzyme activities was noted. It is concluded that ethanol given acutely has a specific stimulating effect on intestinal enzymes involved in lipid absorption.
Considerable attention has been focused in recent years on the effects of ethanol on smallbowel structure and function. In humans chronic exposure to alcohol has been shown to inhibit uptake of folio acid by the jejunum (1) and vitamin B12 by the terminal ileum (2). Chronic exposure to this agent in both man and rats has been shown to cause ultrastructural changes in the small bowel (3). Acute studies in man (4) and in rats (5) have demonstrated impaired transport of amino acids by the intestine. More recently, it has been reported that acute ethanol treatment was associated with scattered hemorrhagic lesions in the rat small bowel in association with reduction of lactase activity (6) and that chronic administration produced blunting of jejunal villi plus reduced activities of lactase and alkaline phosphatase (6). In our laboratory, we have been interested in factors that influence the activities of the smallFrom the Department of Medicine, AlbanyMedical College, Albany, New York. Address for reprint requests: Dr. J.B. Rodgers, Department of Medicine, Albany Medical College, Albany, New York 12208. 354
intestinal, lipid-reesterifying enzymes. These are required for normal absorption of fat by the small bowel. Previous studies have indicated that these enzymatic activities are affected by the amount of lipid presented for absorption (79). Certain toxic agents, such as methotrexate, have been shown to decrease these enzyme activities in association with malabsorption of lipid in vivo (10). The current study of acute exposure to ethanol was done to determine whether this agent has any adverse or stimulating effect on these microsomal lipid reesterifying enzyme activities of the rat intestinal mucosa. To determine whether any alteration caused by ethanol was fairly specific for the enzymes involved in lipid absorption or was part of a more general response of the intestine to this agent, sucrase and lactase assays were also done on jejunal samples. These enzymes are digestive in function and are required for absorption of simple carbohydrate molecules. Their location in the mucosal cell, being basically on the brush border, also differs from that of the lipidreesterifying enzymes. It was felt that if similar Digestive Diseases, Vol. 20, No. 4 (April 1975)
EFFECT OF ETHANOL ON RAT LIPID ENZYMES Table 1. Jejunal Lipid Reesterifying Enzyme Activities in Ethanol-Treated and Glucose-Treated Rats MG-Acyltrans Microsomal protein (rag)*
Specific activity*l-
15.9i2.2
119i18
Ethanol-treated rats (N=7) Glucose-treated rats (N=7) P
16.0• NS
79•
