Regulation and expression of endothelin-1 (ET-1) and ET-receptors in rat epithelial cells of renal and intestinal origin

The hormone endothelin-1 (ET-1) is involved in many functions of the kidney and intestine. In addition to its vasoactive and proliferative effects, ET-1 is involved in the maintenance of water and salt balance, and in drug excretion by influencing the activity of different transporters in the epithelial cells of these two organs. To study ET-1 function and its role in pathophysiological processes in epithelial cells in vitro, we investigated ET-1 and ET-receptor expression and inducibility of ET-1 excretion by cytokines in three rat cell lines of intestinal (IEC-6) and renal (NRK-52E and GERP) origin. Immunocytochemistry showed that all three cell lines express ET-1 and the ET-A and ET-B receptor. ET-1 was expressed intracellularly, and also the ET-A receptor showed a punctate intracellular staining pattern. The ET-B receptor was localized in the membrane, which was confirmed by Western blot analysis. Real-time RT-PCR and ELISA showed that exposure of IEC-6 cells to the cytokines, interleukin-1β (IL-1β) and tumor necrosis factor-α (TNFα), induced ET-1 mRNA expression and excretion, while IL-2 was ineffective. In NRK-52E cells, IL-1β and TNFα induced ET-1 excretion as well. In GERP cells, adequate measurement of cytokine effects on ET-1 excretion was not possible, since ET-1 excretion under non-stimulated conditions was around the lowest level of detection. In conclusion, we showed ET-1 and ET-receptor expression, and inducibility of ET-1 by cytokines in IEC-6, NRK-52E, and GERP cells. These rat intestinal and renal cell lines appear to be suitable for further characterisation of ET-1 function and its role in pathophysiological processes in epithelial cells.