AJP - Renal Physiology, Vol 250, Issue 6 1063-F1072, Copyright © 1986 by American Physiological Society
Effect of ADH on rubidium transport in isolated perfused rat cortical collecting tubules
J. A. Schafer and S. L. Troutman
Unidirectional fluxes of 86Rb+ were measured as an indicator of potassium
transport in isolated rat cortical collecting tubules perfused and bathed
at 38 degrees C with isotonic solutions in which Rb+ replaced K+. Under
control conditions the lumen-to-bath flux (Jl----b) was significantly less
than the bath-to-lumen flux (Jb----l), indicating net Rb+ secretion. Net
secretion increased approximately 180% after addition of 100 microU/ml of
arginine vasopressin (ADH) to the bathing solution, due to a rapid and
reversible increase in Jb----l from 4.6 +/- 0.8 to 9.0 +/- 1.9 pmol X min-1
X mm-1 with no significant change in Jl----b. The ADH effect was completely
inhibited by 2 mM luminal Ba2+. The average transepithelial voltage (Ve)
was not significantly different from zero in the control period but became
lumen negative (-5 to -10 mV) after ADH. With 10(-5) M amiloride in the
lumen Ve was lumen positive (+2 to +4 mV) and was unaltered by ADH or Ba2+,
yet ADH produced a significant but attentuated increase in Jb----l with no
change in Jl----b. The results indicate that ADH augments net K+ secretion
either by an increase in the Ba2+-sensitive conductance of the apical
membrane or by an increase in the electrochemical potential driving force
for net Rb+ secretion through this pathway.
