Studies of the permeability of isolated porcine peritoneum to nutrients: saccharides

Isolated peritoneal membrane, freshly harvested from pigs, was studied in vitro to determine the permeability of the membrane to saccharide nutrients. Studies were performed with glucose and sucrose at various transmembrane gradients ranging from 150 to 600 mosm/liter (mmol/liter) and with polysaccharide at a 300 mosm/liter gradient. Findings indicate that flux of these nutrients across the isolated peritoneum is related to molecular weight and that sufficient kilocalories will traverse the membrane to provide for adequate carbohydrate nutrition (calculated to deliver more than 3000 kcal/day at gradients of 150 mosm/liter). Polysaccharide flux studies suggest that carbohydrate calories may be provided in the form of complex molecules and not only in the form of glucose. Studies of 1:1 serum and polysaccharide mixtures showed the conversion of polysaccharide to glucose by serum in vitro. When rats were given intraperitoneal polysaccharide their blood glucose levels rose promptly although they remained fasting, suggesting an in vivo conversion also occurs. These findings provide support for use of polysaccharides intraperitoneally as means to reduce the osmolarity of fluid administered for nutritional support; this would increase tolerance while still providing ample calories. The in vitro apparatus used in these studies provides a mechanism to study individual nutrients and yields highly reproducible results. These studies add further evidence that intraperitoneal nutrition is feasible.