AJP - Renal Physiology, Vol 250, Issue 2 261-F266, Copyright © 1986 by American Physiological Society
pH sensitivity of the basolateral membrane of the rabbit proximal tubule
B. A. Biagi and M. Sohtell
Conventional microelectrodes were used to study the effects of bath pH and
bicarbonate concentrations on the basolateral membrane potential (Vbl) of
cells from the superficial proximal convoluted (PCT) and proximal straight
(PST) tubules of the rabbit kidney perfused in vitro. Bathing solution pH
was varied over the range of 5.9-7.4 using either control (22-25 mM) or low
bicarbonate (5.0-6.6 mM) Ringer solutions and the appropriate CO2 tensions.
The results show a strong pH dependence of the steady-state values of Vbl
in both the convoluted and straight tubule segments. The pH-dependent
depolarization was approximately 35 mV/pH unit change of the bathing
solution in the acid direction and could be demonstrated in CO2-free
HEPES-buffered solutions. A depolarizing response to increased bath
potassium concentration (HK) was observed that was linearly related to the
absolute value of the Vbl under control conditions. Under acidotic
conditions, reduced HK depolarizations indicate that a decrease in the
relative potassium permeability of the basolateral membrane is the
principle mechanism underlying the effects of bath pH on Vbl.
