DIFFERENTIATION OF MADIN-DARBY CANINE KIDNEY-CELLS DEPENDS ON CELL-CULTURE CONDITIONS

We used Madin-Darby canine kidney (MDCK) cells as a model to study changes in renal epithelial cell structure and function induced by different environments. We identified two cell types, MDCK-1 and MDCK-2, that differ in structure, function and lectin binding. MDCK cells differentiate into MDCK-1 cells in acid and hypertonic culture media, whereas MDCK-2 cells develop in alkaline and hypotonic culture media in subconfluent and young confluent monolayers. Fully differentiated MDCK-1 and MDCK-2 cells cannot reverse their differentiation state in aged confluent monolayers. Relative sodium conductance is increased 48-fold in MDCK-1 cells. MDCK-1 cells acidify their incubation medium, whereas MDCK-2 cells acidify dome fluid. Hypotonic stress further decreases HCO3- concentration in dome fluid. Dome formation increases in higher cell passages; concomitantly the ratio of MDCK-2:MDCK-1 cells increases. Cloned MDCK cell populations become increasingly heterogenous with increasing passage number. We conclude that differentiation in MDCK cells is determined by cell culture conditions.