Disproportionally low clearance of macromolecules from the plasma to the peritoneal cavity in a mouse model of peritoneal dialysis.

Background: This study was performed to establish a model for quantitative measurements of a number of basic peritoneal transport parameters, particularly transperitoneal clearances (Cl) of macromolecules, during mouse peritoneal dialysis.

Methods: Mice were anaesthetized using 3% isofluorane inhalation anaesthesia. The right jugular vein and the left femoral artery were cannulated for infusion and sampling purposes and for registration of (mean) arterial blood pressure. Access to the peritoneal cavity occurred via a thin abdominal catheter (Ø 0.7 mm). About 2.5 ml of either 4% (n = 9) or 1.5% (n = 5) glucose containing PD-fluid were instilled intraperitoneally (i.p.). Dialysate volume was followed vs time using i.p. RISA ((125)I human serum albumin) as a volume marker, after correcting for RISA mass disappearance from the peritoneum, assessed separately (n = 11). Microsampling (10 microl) of plasma and dialysate was performed for determinations of glucose, haematocrit, radioactivity (RISA and (51)Cr-EDTA) and Ficoll.

Results: The i.p. volume vs time curves [V(D)(t)] were, after scaling, similar to those observed in humans (and in rats). Clearance of RISA out of the peritoneal cavity (Cl(out)) was 9.33 +/- 0.83 microl/min and the clearance of RISA to plasma (Cl-->P) and the RISA clearance to the peritoneal cavity (Cl-->D) were 1.49 +/- 0.13 and 0.084 +/- 0.008 microl/min, respectively. The peritoneal transport coefficients for (51)Cr-EDTA and glucose, as well as Cl(out) and Cl-->P, were 13-17% of those previously assessed in 300 g rats, whereas Cl-->D was only approximately 2% of that in rat.

Conclusions: All peritoneal transport parameters measured, except Cl-->D, scaled very well to the corresponding human data. The mechanisms of the disproportionally low clearance of macromolecules from the plasma to the peritoneal cavity in mice remain elusive and warrant further study.