Synthesis and secretion of endothelin in a cortical collecting duct cell line

• Published in: American journal of physiology. Renal physiology Vol. 271; no. 2 Pt 2; pp. F330 - F339
• Main Authors: Todd-Turla, K M, Zhu, X L, Shu, X, Chen, M, Yu, T, Smart, A, Killen, P D, Fejes-Toth, G, Briggs, J P, Schnermann, J B
• Format: Journal Article
• Language: English
• Published: United States 01.08.1996
• Subjects: Animals; Arginine Vasopressin - pharmacology; Base Sequence; Cells, Cultured; Dactinomycin - pharmacology; Endothelins - genetics; Endothelins - metabolism; Hypertonic Solutions - pharmacology; Kidney Cortex; Kidney Tubules, Collecting - cytology; Kidney Tubules, Collecting - drug effects; Kidney Tubules, Collecting - metabolism; Mice; Molecular Sequence Data; Oligonucleotide Probes - genetics; Protein Synthesis Inhibitors - pharmacology; Renal Agents - pharmacology; RNA, Messenger - metabolism
• DOI: 10.1152/ajprenal.1996.271.2.F330
• ISSN: 0002-9513; 1931-857X

Previous experiments have shown that epithelial cells in the renal medulla produce endothelin-1 (ET-1) and possess ETB receptors. It has been suggested that medullary ET-1 may affect water and sodium absorption along the collecting ducts in an autocrine fashion. To study possible mechanisms responsible for the regulation of medullary ET-1 production, experiments were performed in M-1 cells and mIMCD-K2 cells, cell lines derived from cortical and inner medullary collecting ducts of SV40 transgenic mice, grown to confluence on collagen-coated filter inserts. Both cell lines were found to express ET-1 mRNA and to secrete ET almost exclusively into the basolateral medium as long as the transepithelial resistance was high. Inhibition of transcription with actinomycin D was followed by a decline in both ET mRNA [halftime (t1/2) = 30 min] and ET secretion (t1/2 = approximately 90 min). The addition of arginine vasopressin (AVP, 10(-8) M; 2- or 4-h exposure) or incubation of M-1 cells in hypertonic media (+50 mM NaCl, 4- or 6-h exposure) did not significantly alter ET secretion or ET-1 mRNA expression. In contrast, simultaneously increasing AVP(10(-8) M in the basolateral medium) and tonicity (+50 mM NaCl) for 4 h increased ET secretion (from 28.9 +/- 3.9 to 41.8 +/- 3.8 pg.h-1.mg protein-1; P = 0.029, n = 10) and ET-1 mRNA (control = 2,138 cpm/microliter, log of 3.33 +/- 0.048, n = 4; AVP + NaCl = 3,548.1 cpm/microliter, log of 3.55 +/- 0.09; P = 0.045, n = 5). Exposure of M-1 cells to hypertonic media (+50 mM NaCl or 100 mM mannitol) for 24 h was associated with a marked reduction of ET secretion (-83.9% with NaCl and -78.4% with mannitol; P < 0.0001). This reduction was attenuated, but not prevented, by the presence of AVP in the basolateral medium (-40%). ET-1 mRNA, in contrast, did not change with 24-h exposure to hypertonic media and increased when AVP was present. Results are compatible with the concept that generation of ET by collecting duct cells may contribute in a complex and time-dependent fashion to the paracrine control of collecting duct cell function.