AJP - Renal Physiology, Vol 248, Issue 2 266-F271, Copyright © 1985 by American Physiological Society
Electrochemical profile of K+ and Na+ in the amphibian early distal tubule
J. Teulon, P. Froissart and T. Anagnostopoulos
Double-barreled microelectrodes selective to either potassium or sodium
were used to determine the transepithelial potential difference (VTE) and
the intraluminal activity of potassium (alpha LuK) or sodium (alpha LuNa)
in the early distal tubule (EDT) of Triturus waltlii in vivo; luminal
activities were compared with the corresponding plasma ion activities,
alpha PtK and alpha PtNa. The transepithelial equilibrium potentials for
potassium (EK(TE] and sodium (ENa(TE] were computed from the respective
transmural chemical distributions: they were used to assess the
transepithelial electrochemical potential differences [(V-EK)TE and
(V-ENa)TE]. By dividing the raw data into three groups of 30% total tubular
length (0-30, 31-60, 61-90%), the following results were obtained. 1) VTE
increases from +15 to +20 mV (lumen positive) between the first and second
portion of the EDT but remains constant thereafter. 2) The alpha LuK/alpha
PtK ratio decreases steadily along the EDT from 1.92 to 1.66 and then to
1.32. 3) The values of alpha LuNa/alpha PtNa in the same three subdivisions
are 0.79, 0.44, and 0.45. 4) The (V-EK)TE difference is largely positive
along the whole EDT: +32, +33, and +27 mV. 5) The (V-ENa)TE difference
declines from +9 mV (first portion) to values statistically not different
from zero in the last two thirds of the EDT.(ABSTRACT TRUNCATED AT 250
WORDS)
