Regulation of sodium transport in m-1 cells.
Nakhoul, Nazih L., Kathleen S. Hering-Smith, Cecilia T. Gambala, and
L. Lee Hamm.
Department of Medicine, Section of Nephrology, Tulane University
School of Medicine, New Orleans, LA 70112.
APStracts 5:0152F, 1998.
The M-1 cell line, derived from the mouse cortical collecting duct
(CCD), is being used as a mammalian model of the CCD to study sodium
(Na) transport. The present studies aimed to further define the role
of various hormones in affecting Na transport in M-1 cells grown in
defined media. M-1 cells on permeable support, in serum-free media,
developed amiloride-sensitive current 4-5 days after seeding. As
expected for the involvement of epithelial Na channels,, & subunits
of the epithelial sodium channel were identified by RT-PCR. Either
dexamethasone (Dex, 10-100 nM) or aldosterone (Aldo 10-6 -10-7M) for
24 hours stimulated transport. Cells grown in the presence of Aldo
and Dex had higher transport than with Dex alone. Spironolactone
added to Dex media decreased transport. The acute effects of hormones
reported to inhibit Na transport in CCD were also examined. Epidermal
Growth Factor, phorbol esters and increased intracellular Ca+2 with
Thapsigargin did not alter transport. Arginine Vasopressin caused a
transient increase in transport (probably Cl- secretion), which was
not amiloride sensitive. Also, the protease inhibitor aprotinin
decreased Na transport; in aprotinin treated cells, trypsin
stimulated transport.
This study demonstrates that adrenal steroids (Dex > Aldo) stimulate
Na transport in M-1 cells. At least part of this response may
represent activation of mineralocorticoid receptors based on an
additive effect of Dex and Aldo, and inhibition by spironolactone.
Responses to immediate-acting hormones is limited. However, an
endogenous protease activity, which activates sodium transport, is
present in these cells.
Received 17 October 1997; accepted in final form 27 August 1998.
APS Manuscript Number F334-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 21 September 1998