Factors affecting icodextrin peritoneal transport in vitro.

We undertook in vitro experiments to examine the importance of mesothelium and interstitium in icodextrin (7.5 g/dL) transport and the change in that transport caused by gentamicin and methylglyoxal. Rabbit peritoneum, a modified Ussing chamber and a mathematical model of mass transport were used. Transfer from the interstitial to mesothelial side of the membrane (I-->M) and in the opposite direction (M-->I), expressed as a diffusive permeability coefficient P, was determined in control series, after chemical modification of the peritoneum by sodium deoxycholate, and after introduction of gentamicin and methylglyoxal. We also investigated the thickness of native tissue 75 minutes into the study and after use of sodium deoxycholate. In the control series, icodextrin I-->M transport increased by 50%, but M-->I transport remained stable [15-60 min vs. 75-120 min. I-->M P, 0.32 +/- 0.04 x 10(-4) cm x s(-1) (standard error of the mean); M-->I P, 0.19 +/- 0.03 x 10(-4) cm x s(-1)]. After application of sodium deoxycholate, I-->M transport was observed to increase by 21% and M-->I by 192% as compared with the 2nd hour of the control series. Gentamicin caused a rise of M-->I transport by 21% without a change of I-->M. We observed no difference in p values (I-->M and M-->I) after application of methylglyoxal. Mean thickness before and 75 minutes into the study was 4.96 +/- 0.28 microm for mesothelium and 62.09 +/- 2.40 microm for the whole peritoneum. Sodium deoxycholate reduced the mesothelium thickness by 20% and increased the peritoneum thickness by 37%. The present study confirms that, in vitro, icodextrin I-->M peritoneal transport changes with time, but M-->I is constant. Asymmetry of glucose polymer diffusion is observed. I-->M predominates over M-->I. Chemical modification of the peritoneum by sodium deoxycholate (I-->M and M-->I directions) and by gentamicin (M-->I direction only), but not by methylglyoxal, intensifies icodextrin transport. Sodium deoxycholate causes exfoliation of the mesothelium and looseness of the interstitium.