EVALUATION OF AN EXPERIMENTAL RAT MODEL FOR PERITONEAL-DIALYSIS - FLUID AND SOLUTE TRANSPORT CHARACTERISTICS

The aim of this study was to develop a reference model of fluid and so lute transport during experimental peritoneal dialysis in rats, which would simulate the conditions of clinical dialysis in CAPD patients as much as possible. For this purpose a 4-h dialysis study was performed in 13 normal Sprague-Dawley rats with conventional glucose solutions (Dianeal 1.36% solution, n = 6 and Dianeal 3.86% solution, n = 7) and a protocol and methods like those used in clinical dwell studies. The dilution of a marker, radioactive human serum albumin (RISA), was used to determine the intraperitoneal dialysate volume with corrections fo r the elimination of RISA from the peritoneal cavity and sample volume s. The isovolumetric method was employed to calculate the diffusive ma ss transport coefficients. To compare our data with reference values i n CAPD patients, the data were scaled by a factor calculated as a rati o of the dialysate volume in CAPD to the dialysate volume in the rats. In a separate series of experiments the intraperitoneal hydrostatic p ressure was monitored with increasing infusion volumes. The fluid tran sport characteristics, described as the percentage changes of the init ial intraperitoneal volume, were essentially comparable to those in CA PD patients. However, the intraperitoneal volume curves were shifted m ore to the left than were the reported values in CAPD patients. The sc aled diffusive mass transport coefficient for urea was similar to that in CAPD patients. However, the transport of other solutes, in particu lar glucose, was faster in the rats than in CAPD patients. The intrape ritoneal hydrostatic pressure increased exponentially with increasing infusion volume relative to body weight and was 0.3-0.9 mmHg with the standard infusion volume of 30 ml in the present study. The intraperit oneal hydrostatic pressure in the rats receiving 30 ml of fluid intrap eritoneally was lower than the reported intraperitoneal pressure in CA PD patients using 21 of dialysis fluid. We conclude that the present e xperimental model of peritoneal dialysis in the rat with a protocol an d methods similar to those used in clinical studies, after appropriate scaling, seems to have fluid and solute transport characteristics tha t resembled those in clinical peritoneal dialysis, but considerable di fferences were also found.