In patients with end-stage renal disease on peritoneal dialysis, the peritoneum is effectively utilized as an endogenous semipermeable membrane. Chemical agents may alter the structure of the peritoneum and induce changes in its transfer properties. The purpose of our in vitro study was to compare the influence of sodium hyaluronan (a cytoprotective glycosaminoglycan, 2000 kDa, 40 mg/dL) and sodium deoxycholate (an intense oxidative stress factor, 414 Da, 104 mg/dL) on the transfer of insulin (5.8 kDa, 100 mg/dL) and albumin (68 kDa, 1000 mg/dL) through isolated rabbit parietal peritoneum. We used a mathematical model to calculate the transport rate of solutes from the interstitial to the mesothelial side of peritoneal membrane (I-->M) and in the opposite direction (M-->I) in three separate series of experiments: Control conditions without chemical agents Before (15-60 minutes) and after (75-120 minutes) introduction of sodium hyaluronan into the experimental system Before (15 -75 minutes) and after (90-150 minutes) introduction of sodium deoxycholate into the experimental system The results are expressed as a diffusive permeability coefficient P in centimeters per second. During the 120 minutes of the control stage, the rate of insulin and albumin bidirectional passage remained constant. Values of P +/- standard error of the mean did not correlate with the molecular weight of the compounds and measured 0.145 +/- 0.033 x 0.0001 cm/s and 0.146 +/- 0.022 x 0.0001 cm/s for insulin, and 0.271 +/- 0.056 x 0.0001 cm/s and 0.315 +/- 0.057 x 0.0001 cm/s for albumin in the I-->M and M-->I transport directions respectively. Application of sodium hyaluronan did not change the bidirectional transport of either solute. However sodium deoxycholate caused the values of P to increase by 142% (p < 0.05) for insulin I-->M transfer and by 102% (p < 0.02) for insulin M-->I transport. Albumin passage increased by 193% (p < 0.01) for both transfer directions. We conclude that, in vitro, sodium deoxycholate but not sodium hyaluronan increases the bidirectional peritoneal transport of insulin and albumin. In the case of larger molecular weight solutes, the modification is greater.