Prostaglandin e2 inhibits nak2cl cotransport in medullary thick
ascending limb cells .
Kaji, Deepak M., Herbert S. Chase, Jr., John P. Eng, and J. Diaz.
Department of Medicine, V.A. Medical Center, Bronx, New York, 10468
and Mount Sinai School of Medicine, New York, NY 10029; and College
of Physicians and Surgeons, Columbia University, New York, NY
10032
APStracts 3:0033C, 1996.
PGE2 is known to inhibit transepithelial Cl transport in mTAL, but the
mechanism of inhibition or the transport pathway affected has not
been identified. We undertook this study to examine the effect of
prostaglandin E2 on NaK2Cl cotransport in the mouse medullary thick
ascending limb cells in culture. In nanomolar concentrations, PGE2
inhibited the Na and Cl dependent, bumetanide-sensitive K influx by
45%, and this inhibition was also observed in the presence of 3 mM
ouabain. While PGE2 also inhibited ouabain sensitive K flux, that
inhibition was abolished in the presence of apical nystatin,
suggesting that the pump inhibition was secondary to diminished Na
entry into the cells. The effect of PGE2 was concentration dependent.
Inhibition was observed at a concentration of <1 nM and half
maximal effect was observed at 2.5 nM. The effect of PGE2 was not
mediated by an action on cytosolic calcium, because cytosolic calcium
was unchanged after the addition of PGE2. PGE2 reduced the Vmax for
the cotransporter, but had no effect on the affinity of the
cotransporter for external Na, K or Cl. Specific [3H] bumetanide
binding was reduced in the presence of PGE2, suggesting that PGE2
affected bumetanide-sensitive K influx by downregulating the number
of functioning NaK2Cl cotransporters. These results suggest that the
NaK2Cl cotransport in the mTAL cells may be under tonic inhibitory
control of PGE2.
Received 11 October 1995; accepted in final form 2 January 1996.
APS Manuscript Number C615-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 January 96