Epithelial organization and hormone sensitivity of toad urinary bladder cells in culture

Two continuous cell lines (TB-M and TB-6c) derived from epithelial cells of the toad urinary bladder form epithelia in culture that manifest hormone-sensitive transepithelial transport. Development of transepithelial electrical resistance (R) and transport rate (ISC) are dependent on time and density of cells seeded, but steady-state ISC and R are characteristic for each cell line and independent of seeding density. Some responses of intact toad bladder are preserved in culture, whereas others are altered or absent. Neither cell line responds to vasopressin. Analogues of cAMP increase sodium transport and urea permeability in both cell lines but do not affect water permeability. The intramembrane particle aggregates associated with the vasopressin- and cAMP-induced increase in water permeability of the intact bladder could not be detected in the cell lines. Aldosterone increases sodium transport in both cell lines, and the time course and concentration dependence of the response to aldosterone are similar to those of the intact bladder. The relative effect of a series of steroids on ISC reveals corticosterone to be a more potent mineralocorticoid in cultured cells than in the intact bladder.