BACKGROUND: Congenital absence of alpha-galactosidase in Fabry disease leads eventually to renal failure. Fabry disease is an attractive candidate for gene therapy, but uptake mechanisms of the enzyme must be understood for it to be used in treating patients with Fabry disease. METHODS: Immortalized human renal epithelial cells from three regions of the tubule were grown in culture on collagen-coated Transwell filters and were incubated with recombinant alpha-galactosidase protein placed at either the luminal or basolateral side of the cells. Uptake into cells was measured, and kinetic studies were performed. Blocking experiments were done with mannose 6-phosphate. RESULTS: Uptake from the basolateral side of the filters predominated in all three cell types. Only in distal tubule cells was mannose 6-phosphate able to block uptake to any degree. The kinetic data reveal a high Km for both luminal and basolateral cell surfaces. CONCLUSIONS: These data suggest that to correct the renal phenotype in Fabry disease, high levels of the enzyme will be need to be delivered to kidney cells. This will likely best be achieved with local administration of a vector containing the transgene directly to the kidney.