Effect of Chronic Ethanol Feeding on Digestive Enzyme Synthesis and mRNA Content in Rat Pancreas

Abstract

Chronic ethanol ingestion is a primary factor in the development of pancreatitis in humans. Alterations in both enzyme secretion and protein synthesis have been implicated as causative factors. We determined the effect of chronic ethanol feeding on the content and synthesis rates of digestive enzymes in dispersed acini from rats that were pair-fed isocaloric diets with or without ethanol for 3-6 months. Total protein content and synthesis were unchanged. The relative synthetic rates of individual digestive enzymes were analyzed using scanning laser densitometry of 1-D sodium dodecylsulfate (SDS) gels. The content of all measurable digestive enzymes except amylase increased in acini from ethanol-fed rats. Relative synthetic rates were examined in pancreatic acini labeled in vitro with [35S]methionine. Liquid scintillation counting of radiolabeled digestive enzymes extracted from gel slices revealed that amylase synthesis in ethanol-fed rats decreased 2.8-fold compared with controls whereas the synthetic rates of proelastase 1 and 2, chymotrypsinogen, and trypsinogen increased by 1.5-, 1.4-, 1.8-, and 1.6-fold, respectively. Total cellular RNA was extracted from control and ethanol-fed rats and subjected to Northern and dot blot analysis. Amylase mRNA decreased in ethanol-fed rats whereas chymotrypsinogen and trypsinogen mRNA content increased, indicating that the effect of ethanol on expression of these genes was regulated at a step prior to translation. Elastase mRNA content was not altered, suggesting that the increased synthesis of proelastase may be regulated posttranscriptionally.