Metabolic substrates alter attachment and differentiated functions of proximal tubule cell culture

Proximal tubules cultured in vitro gradually lose their differentiated functions. Because standard culture media lacks several substrates important for renal proximal tubule oxidative metabolism, whether a mixture of substrates including butyrate, alanine, and lactate (BAL) would modify growth and/or differentiated function of proximal tubular cells in culture was examined. Tubules cultured in media supplemented with 2 mM butyrate, alanine, and lactate exhibited enhanced attachment but did not exhibit an altered growth rate. Higher levels of phosphoenolpyruvate carboxykinase and leucine-amino peptidase were sustained, although these activities were still diminished in comparison with that in fresh tubules. Sodium-dependent glucose uptake and dome formation--other reflections of epithelial cell differentiated function--also were enhanced. These studies demonstrate that the substrates used to culture proximal tubules can modify both their attachment and their manifestation of differentiated function in culture.