Four-week ethanol drinking increases both thyrotropin-releasing hormone (TRH) release and content in rat pancreatic islets

Ethanol exerts profound effects on the endocrine and exocrine pancreas. Som e effects of chronic alcohol consumption on insulin secretion in response t o glucose load are similar to those of TRH gene disruption. TRH is present in insulin-producing B-cells of the islets of Langerhans; its role in this location is still not fully explored. To examine the possible effect of lon g-tern in vivo ethanol treatment on pancreatic TRH we compared three groups of rats: a 10% (wt:vol) ethanol-drinking group (E), absolute controls (AC) and pair-fed (PF) group with solid food intake corresponding to that of E. The fluidity of pancreatic membranes was not affected by chronic in vivo e xposure of rats to ethanol, but was significantly decreased in PF group. Fo ur-week treatment resulted in significantly higher TRH content in isolated islets of the E group and increased basal and 80 mM isotonic ethanol-induce d secretion compared to AC and PF. Plasma levels of insulin, C-peptide, IGF -I, and glycemia were,,however, not affected by ethanol treatment. Cell swe lling, which can be induced by the presence of permeants (e.g. ethanol) in an isotonic extracellular medium, is a strong stimulus for secretion in var ious types of cells. In the present study, isosmotic ethanol (40, 80, and 1 60 mM) induced dose-dependent release of TRH and insulin from adult rat pan creatic islets in vitro. The same concentrations were not effective when ap plied in a hyperosmotic medium (addition of ethanol directly to the medium) , thus indicating the:participation of cell swelling in the ethanol-induced secretion. In conclusion, chronic ethanol treatment significantly affected pancreatic TRH and this effect might be mediated by cell swelling. The rol e of these changes in the profound effect of:ethanol on the endocrine and e xocrine pancreas remains to be established.