The potential advantages of the peritoneum as an insulin delivery site for an implanted mechanical pancreas are reviewed. During embryogenesis in humans, the development of the pancreas and liver are closely related such that, in the adult, all endogenous insulin secreted by the pancreas passes directly to the liver before entering the peripheral circulation. This anatomic relationship permits the direct modulation of absorbed nutrients from the gut by both the liver and pancreatic hormones. Preliminary studies in the dog indicate that at least a portion of insulin infused into the peritoneal space enters the hepatic portal vein before entering the peripheral circulation, thereby simulating normal pancreatic insulin secretion.
Infusion of insulin directly into the peritoneum in humans has demonstrated that (1) insulin absorption is rapid (within minutes), (2) it results in appropriate meal-related peaks in peripheral insulin concentration, and (3) the insulin has biologic activity in suppressing meal-induced hyperglycemia. Furthermore, analysis of the absorbed insulin pattern indicates that approximately 50% of the delivered insulin is removed before entering the peripheral circulation, compatible with hepatic insulin removal. In addition, insulin delivered into the peritoneum in diabetic individuals may result in a reduction in meal-related glycemic excursions, compared with a similar quantity of NPH insulin delivered subcutaneously. Thus, the peritoneum may be a rational alternative to both the intravenous and subcutaneous delivery sites for an implanted insulin delivery system,
