Proximal tubule characteristics of cultured human renal cortex epithelium

Cultured human renal cortical epithelial cells (NHK-C) were examined for functional and morphologic characteristics of the proximal tubule. Cultures were established by using cells isolated by progressive enzymatic dissociation from the extreme outer cortex of the normal human kidney. Cells were subcultured and used at passages 3 through 8. Cell uptake of alpha-methyl-D-glucoside (AMG), inorganic phosphate (Pi) and L-alanine was found to be dependent on the presence of Na+ in the incubation medium, and uptake increased with incubation time up to 30 minutes. Na+-dependent AMG uptake was inhibited 67% by phlorizin (1 mmol/L), and Pi uptake was inhibited 89% by parathyroid hormone (PTH) (10(-6) mol/L). Intracellular cyclic adenosine monophosphate was increased 28-fold after exposure to 10(-6) mol/L PTH but was increased only 2-fold by the same concentration of vasopressin. The cells exhibited endocytotic activity and possessed maltase, leucine aminopeptidase, and gamma-glutamyltranspeptidase, enzymes located exclusively in the brush border membranes of proximal tubule cells. NHK-C cultures were structurally heterogeneous, made up of a mixed-cell population with predominant epithelial-like morphology. Epithelial cells had cuboidal form, solitary cilia, and short, irregularly distributed apical microvilli. These cultures also formed multicellular hemicysts, but only through passage 3. NHK-C cultures showed a dramatic attenuation of proliferative activity at passages 8 through 10. These data show that subcultured cells derived from the outer cortex of the normal human kidney retain a number of functional characteristics typical of the proximal tubule.