AJP - Renal Physiology, Vol 243, Issue 1 81-F95, Copyright © 1982 by American Physiological Society
Ionic conductive properties and electrophysiology of the rabbit cortical collecting tubule
R. G. O'Neil and E. L. Boulpaep
The Na, K, and Cl conductive properties and the electrophysiological
variability of the rabbit isolated cortical collecting tubule were assessed
by evaluating the effect of single-ion substitutions on the transepithelial
potential difference, Vte, and the transepithelial conductance, Gte. The Na
permeability (and conductance) of the tight junction and basolateral cell
membrane appeared to be low. However, a significant but variable
amiloride-sensitive Na conductance was identified at the apical cell
membrane. Although this Na conductance accounts for less than 10% of the
Gte, variations in this conductance caused major alterations in the active
transepithelial Na current and the Vte. A highly variable K permeability
(and conductance) was also identified at the apical cell border and may
account for some of the variability in Vte and Gte. This probably provides
a pathway for K secretion from cell to lumen. The K permeability of the
tight junction and basolateral cell membrane appeared to be relatively low.
In contrast, the Cl permeability (and conductance) of the tight junction,
and perhaps of the basolateral cell membrane, appeared to be high but
variable and to account for the major fraction of the Gte and its
variability. It is concluded that variations in the Na and K conductance of
the apical cell membrane and the Cl conductance of the tight junction and
basolateral cell membrane predominantly account for the variations in the
electrophysiological properties of the cortical collecting tubule.
