Experimental peritoneal dialysis in Sprague-Dawley rats using conventional or low sodium dialysis fluids

During peritoneal dialysis, sodium is transferred in a paracellular fashion via inter-endothelial nanochannels from the blood plasma water to the dialysate and, initially, dialysate sodium concentrations are also diluted by free water transport across endothelial aquaporin-1 channels. These experiments were performed to evaluate the relative contributions of free water transport, convective- and diffusive transfer on dialysate sodium. Based on our findings, we devised a simple method to quantify ultrafiltration by analyzing the initial decline in dialysate sodium concentration, commonly referred to as the "sodium dip."

Methods
Experimental peritoneal dialysis was performed in healthy anesthetized 9 weeks old Sprague-Dawley rats using either 20 mL conventional (134 mmol/L) or low-sodium (125 mmol/L) peritoneal dialysis fluids utilizing a dwell time of 120 minutes. Blood plasma was analysed before and after dialysis to measure Na+, K+, Cl-. Ca++, glucose, urea, creatinine, and total CO2. 125I-albumin and 51Cr-EDTA were added to the dialysate to estimate intra-peritoneal volume and to assess small solute diffusion capacity, respectively. Samples (20 μL) of dialysate and blood were collected at multiple time-points during the dialysis session and analyzed on a gamma counter. All data in this dataset are unprocessed.