Transport Functions in a Bioartificial Kidney under Uremic Conditions

Abstract

A bioartifical kidney, a confluent monolayer of renal tubular cells attached to a permselective synthetic membrane, may some day substitute for the failing renal function. In such a device, the cells would have to exhibit transport properties when exposed to uremic plasma. To test the feasibility of a bioartificial kidney, LLC-PK₁ cells derived from the proximal tubule were grown to confluence on microporous, cellulose nitrate membranes and transepithelial transport of inulin, glucose and tetraethylammonium (TEA) was investigated with standard tissue culture medium and with the hemofiltrate obtained from a uremic patient. Inulin, which is neither reabsorbed nor secreted by renal epithelial cells, did not diffuse through the LLC-PK₁ monolayer in either tissue culture fluid or hemofiltrate. Glucose was preferentially reabsorbed and TEA was preferentially secreted in both media. In hemofiltrate, LLC-PK₁ cells reabsorbed glucose at the same rate as in tissue culture fluid but secreted TEA at a significantly higher rate. This difference was related to the pH of the fluids since it was abolished by correction to the same pH value. For both solutes, the passive transepithelial leakage was significantly lower in hemofiltrate. We conclude that LLC-PK₁ cells retain their reabsorbtive and secretory transport characteristics under uremic conditions.