PERITONEAL SURFACE-AREA AND ITS PERMEABILITY IN RATS

Objective: Evaluation of peritoneal surface area and its permeability during dialysis in rats of various ages. Design: Study I: planimetry o f peritoneum and its topographic areas was performed in 47 rats of var ious ages (8 - 30 weeks). Study II: net ultrafiltration (UF), dialysat e-to-serum ratios for urea, creatinine, albumin, and total protein as well as their peritoneal permeability coefficients, were measured duri ng a 1-hour peritoneal exchange with Dianeal 2.5%, in 21 rats of diffe rent ages (9 - 30 weeks) and with various peritoneal surface areas. An imals: Male Wistar rats. Results: The peritoneal surface area in rats increases during aging, but young animals with lower body weight have a relatively larger peritoneal surface area than older, larger animals . The area of the topographic fragments of peritoneum expressed as a p ercentage of the total peritoneal surface is steady during aging. Effi ciency of transperitoneal water removal expressed as net UF per amount of absorbed glucose declines in older animals, with larger peritoneal surface areas. Dialysate/serum ratio of solutes transported from bloo d to dialysate is proportional to peritoneal surface area. Permeabilit y coefficient (K) of peritoneum to urea and creatinine is unchanged du ring the aging of animals. However peritoneal permeability (K) to albu min increases during aging, with the opposite tendency for total prote ins. Conclusions: Kinetics of peritoneal dialysis in rats of different ages is determined by peritoneal surface area and permeability of per itoneum to individual solutes.