Role of the microcirculation in ethanol-induced mucosal injury in the dog.

The aim of the present study was to assess the role of the intestinal microcirculation in the mucosal injury induced by intraenteric ethanol. Mucosal injury was assessed histologically in the ileum and jejunum and quantitated in the ileum by measuring clearance of albumin (37 A, radius) and beta-lactoglobulin A (27 A, radius). A steady-state analysis of the forces and flows governing transcapillary fluid movement was performed in autoperfused segments of jejunum and ileum. In the jejunum and ileum ethanol induced the formation of subepithelial blisters in 10%-40% of the villi. In the ileum, ethanol (5%, vol/vol) increased the clearance of both proteins but the ratio of lactoglobulin to albumin clearance decreased, indicating that the selectivity of the mucosal membrane was diminished. In both the jejunum and ileum ethanol produced similar alterations in the forces governing transcapillary fluid exchange. Ethanol increased the filtration coefficient (35%-40%), but did not alter the osmotic reflection coefficient of intestinal capillaries, indicating that surface area increased whereas vascular permeability was not affected. Capillary pressure increased (2-3 mmHg) whereas interstitial (lymph) protein concentration decreased resulting in an increase in the transcapillary oncotic pressure gradient (1-2 mmHg). The net result of the alterations in the forces governing transcapillary movement was only a doubling of the transcapillary filtration rate (lymph flow). It is concluded that the ethanol-induced increase in mucosal permeability to macromolecules cannot be explained solely on the basis of alterations in the forces and flows governing transcapillary fluid exchange in the small intestine.