AJP - Renal Physiology, Vol 250, Issue 2 267-F272, Copyright © 1986 by American Physiological Society
Electrophysiology of basolateral bicarbonate transport in the rabbit proximal tubule
B. A. Biagi and M. Sohtell
Conventional microelectrodes were used to examine the electrogenic pathways
for bicarbonate transport across the basolateral membranes of proximal
convoluted (PCT) and straight (PST) tubule segments of the rabbit kidney
perfused in vitro. When bath bicarbonate concentration was reduced from 22
to 6.6 mM at a constant pH, transient depolarizations lasting several
seconds with a peak value of approximately 15 mV were seen in both tubule
segments. Acetazolamide (0.1 mM) in the lumen and bath solutions reduced
the magnitude and increased the duration fo this response. The final pH of
the bathing solution influenced both the peak height and steady-state
values of the intracellular potential when bicarbonate concentration was
reduced either with constant CO2 or with an increase in CO2. Reducing bath
sodium concentration by replacement with either tetramethylammonium or
N-methyl-D-glucamine resulted in a sustained depolarization of both PCT and
PST cells. This response was inhibited by the addition of 10(-4) M
4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate (SITS) in the bathing
solution. By analogy with bicarbonate transport in rat and amphibian
proximal tubules, these data suggest that bicarbonate exit across the
basolateral membrane of the rabbit proximal tubule is electrogenic and
coupled to sodium and that basolateral bicarbonate exit can be inhibited by
both acetazolamide and SITS in the bathing solution.
