Synthesis and secretion of endothelin in a cortical collecting duct cell line.
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.
Todd-Turla
K M
KM
Department of Physiology, University of Michigan, Ann Arbor 48109, USA.
Zhu
X L
XL
Shu
X
X
Chen
M
M
Yu
T
T
Smart
A
A
Killen
P D
PD
Fejes-Toth
G
G
Briggs
J P
JP
Schnermann
J B
JB
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001483:Base Sequence; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D016232:Endothelins / Q000235:genetics / Q000378:metabolism*; D006982:Hypertonic Solutions / Q000494:pharmacology; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes / Q000235:genetics; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D012076:Renal Agents / Q000494:pharmacology
D016232:Endothelins; D006982:Hypertonic Solutions; D015345:Oligonucleotide Probes; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D012076:Renal Agents; D001127:Arginine Vasopressin; D003609:Dactinomycin