Synthesis and secretion of endothelin in a cortical collecting duct
cell line.
Todd-Turla, Karyn M., Xiulian L. Zhu, Xiaoquan Shu, Min Chen, Tingxi
Yu, Ann Smart, Paul D. Killen, Geza Fejes-Toth, Josie P. Briggs, and
Jurgen B. Schnermann.
Departments of Physiology, Pathology, and Internal Medicine of the
University of Michigan, Ann Arbor, Michigan, and Department of
Physiology, Dartmouth Medical School, Lebanon, New Hampshire
APStracts 3:0068F, 1996.
Previous experiments have shown that epithelial cells in the renal
medulla produce endothelin1 (ET1) and possess ETB receptors. It has
been suggested that medullary ET1 may affect water and sodium
absorption along the collecting ducts in an autocrine fashion. To
study possible mechanisms responsible for the regulation of medullary
ET1 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
ET1 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 (t1/2 30 min) and ET secretion (t1/2 about 90 min). The
addition of AVP (10-8 M; 2 or 4 hour exposure) or incubation of M-1
cells in hypertonic media (+ 50 mM NaCl, 4 or 6 hour exposure) did
not significantly alter ET secretion or ET1 mRNA expression. In
contrast, simultaneously increasing AVP (10-8 M in the basolateral
medium) and tonicity (+ 50 mM NaCl) for 4 hours increased ET
secretion (from 28.9 +/- 3.9 pg/h.mg protein to 41.8 +/- 3.8 pg/h.mg
protein; p = 0.029; n=10) and ET1 mRNA (control: 2138 cpm/[mu]l, log:
3.33 +/- 0.048, n=4; AVP + NaCl: 3548.1 cpm/[mu]l, log: 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 hours 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 %).
ET1 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.
Received 3 August 1995; accepted in final form 7 March 1996.
APS Manuscript Number F255-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 16 April 96