Evidence for location of the cystic fibrosis transmembrane
conductance regulator in human placental apical membrane
vesicles..
Fallern, Don P., Denise A. Egan, and Michael P. Ryan.
Department of Pharmacology, University College Dublin, Foster
Avenue, Blackrock, Co. Dublin, Ireland.
APStracts 2:0087C, 1995.
Ion transport (36Cl uptake) and immunochemical studies were undertaken
to detect the cystic fibrosis transmembrane conductance regulator
(CFTR) in apical membrane vesicles prepared from human placenta. 36Cl
uptake into membrane vesicles was studied in the absence and presence
of inwardly directed potassium gradients and valinomycin (Ko = Ki and
Ko > Ki). The sensitivities of 36Cl uptake to the inhibitors 4,4
-diisothiocyanostilbene-2,2 -disulfonic acid (DIDS), bumetanide and
diphenylamine-2-carboxylate (DPC) were investigated. Each compound
significantly inhibited uptake under both sets of conditions.
Additional inhibition of 36Cl uptake was found when the compounds
were added together indicating that they were acting at least partly
on different components of the 36Cl uptake. The DIDS and bumetanide
-insensitive component of transport was more selective for chloride
than iodide. These findings suggested that this component may, at
least in part, represent Cl transport via CFTR. Addition of ATP-g-S
(0.8 mM) lead to a decrease in total 36Cl uptake but masked in the
overall decrease was an increase in the DIDS and bumetanide
insensitive component of 36Cl uptake. Western blot analysis of the
apical membrane proteins with an antibody specific for a region of
human CFTR detected a protein band of approx. 190 kDa. These ion
transport and immunochemical studies provide evidence that CFTR is
located in human placental apical membrane vesicles.
Received 13 September 1994; accepted in final form 13 January
1995.
APS Manuscript Number C550-4.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 28 February 1995.