Molecular charge influences transperitoneal macromolecule transport.

The influence of molecular charge on macromolecule transport during peritoneal dialysis was assessed by determining transperitoneal transport rates for fluorescent-labeled macromolecules (molecular radii from 15 to 40 A) that differed only in molecular charge: neutral dextran, anionic dextran sulfate and cationic diethylaminoethyl (DEAE) dextran. The test macromolecules were infused into the bloodstream of unanesthetized New Zealand White rabbits at a constant rate, and isotonic dialysis solution (40 ml/kg) was instilled into the peritoneal cavity. Blood and dialysate samples were taken hourly over a four hour dwell. Transperitoneal transport rates were assessed by calculating both the dialysate to plasma concentration ratio at four hours and the permeability-area product for the peritoneum, the latter parameter determined from the increase in the dialysate concentration with time. Transport rates for DEAE dextran were less (P < 0.05) than those for both neutral dextran and dextran sulfate; transport rates for neutral dextran and dextran sulfate were not different. Moreover, transperitoneal transport rates for fluorescent-labeled DEAE dextran were not affected by adding unlabeled DEAE dextran to the intravenous infusion solution, an observation suggesting that low transport rates for DEAE dextran were not due to its binding to plasma protein. We conclude that molecular charge is a determinant of transperitoneal macromolecule transport.