Fluorescence imaging study of organic anion transport from renal
proximal tubule cell to lumen.
Miller, David S., Susan Letcher, and David M. Barnes.
Intracellular Regulation Section, Laboratory of Cellular and
Molecular Pharmacology, National Institute of Environmental Health
Sciences, National Institutes of Health, Research Triangle Park,
North Carolina 27709, Mount Desert Island Biological Laboratory.
Salsbury Cove, ME 04672
APStracts 3:0087F, 1996.
The mechanisms driving organic anion transport from cell to lumen were
studied in intact killifish proximal tubules using fluorescence
microscopy. Three fluorescent substrates were used: 1) fluorescein,
2) carboxyfluorescein (CF), generated intracellularly from
carboxyfluorescein diacetate (CFDA), and 3) bimane-S conjugates,
generated intracellularly by conjugation of monochlorobimane (MCB)
with glutathione and subsequent metabolism. The latter two substrates
by-passed the basolateral uptake mechanism, allowing direct study of
lumenal transport mechanisms. At steady state, for all three
substrates, lumenal fluorescence was 2-3 times higher than cellular
fluorescence. With FL as substrate, addition of p- aminohippurate
(PAH) or probenecid to the incubation medium reduced cellular and
lumenal fluorescence to roughly the same extent. With CFDA or MCB as
substrate, PAH and probenecid only slightly reduced cellular
fluorescence, but greatly reduced lumenal fluorescence. MCB blocked
transport of FL from cell to lumen; CFDA blocked transport of bimane
-S conjugates from cell to lumen. Finally, depolarizing tubule cells
with high potassium medium did not affect the steady state lumen to
cell distribution of FL, CF or bimane-S conjugates. These results
show that organic anion transport from cell to lumen is mediated and
uphill, but not sensitive to the electrical potential difference
across the lumenal membrane.
Received 19 September 1995; accepted in final form 25 March 1996.
APS Manuscript Number F316-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 May 96