Toad urinary bladder epithelial cells in culture: maintenance of epithelial structure, sodium transport, and response to hormones.

Epithelial cells from the toad urinary bladder have been grown in continuous culture. Many of the cells resemble the granular cell type of the urinary bladder. They form an epithelium with typical tight junctions and gap junctions. The transport properties of two cell lines have been examined. When cells of the line designated TB-M or of line TB-6c are grown on collagen-coated nucleopore filters, epithelia are formed that have transepithelial potential differences of 40 and 20 mV, resistances of 5000 and 10,000 omega-cm2, and short-circuit currents (ISC) of 8.5 and 2.5 muA/cm2, respectively. Net mucosa to serosa sodium transport accounts for all of ISC in line TB-M and for 70% of ISC in line TB-6c. Vasopressin, which stimulates adenylate cylase and ISC in the intact bladder, has no effect on the cells in culture. Cyclic AMP stimulates ISC and lowers resistance in both lines. Aldosterone stimulates ISC in both lines. This is accompanied by a fall in resistance in line TB-M and no change in resistance in line TB-6c. Amiloride inhibits ISC in TB-M cells under basal conditions and after stimulation by aldosterone. In line TB-6c amiloride has no effect under basal conditions but lowers ISC of aldosterone-treated cells to the basal level. Thus, the cells have retained the ability to form oriented, high-resistance epithelial membranes that manifest hormone-sensitive transepithelial sodium transport.