AJP - Renal Physiology, Vol 251, Issue 1 141-F149, Copyright © 1986 by American Physiological Society
Active tetraethylammonium uptake across the basolateral membrane of rabbit proximal tubule
J. B. Tarloff and P. H. Brand
Tetraethylammonium (TEA) uptake was measured in isolated, nonperfused
rabbit S2 proximal tubule segments. The TEA cell-to-bath concentration
ratio in bicarbonate-Ringer bathing medium was 10-fold higher than that
predicted by passive equilibration according to the basolateral
electrochemical potential, indicating that TEA uptake is an active process
as reported by previous investigators. Removing bicarbonate and CO2 reduced
TEA uptake to 22% of control. When bicarbonate-CO2 was replaced by HEPES-O2
or butyrate-O2, TEA uptake was unaltered, but uptake was inhibited when the
major buffer anion was omitted. In the presence of 10(-4) M ouabain and
bicarbonate-CO2, the TEA cell-to-bath concentration ratio was reduced to
20% of control. TEA uptake in the absence of bicarbonate and CO2 was
unaltered by the addition of 10(-4) M ouabain. TEA uptake was inhibited
when the bathing medium contained 0 mM K+ or 2 mM Ba2+. These data 1)
demonstrate that active basolateral TEA uptake is dependent on medium
buffer capacity and 2) support the concept that a portion of TEA uptake
occurs via a passive equilibration pathway.
