AJP - Cell Physiology, Vol 259, Issue 1 C103-C109, Copyright © 1990 by American Physiological Society
Transepithelial acidification by cultures of rabbit proximal tubules grown on filters
S. M. Ford, P. D. Williams, S. Grassl and P. D. Holohan
Department of Pharmaceutical Sciences, St. John's University, Jamaica.
Transepithelial acidification in the proximal tubule occurs by the
simultaneous actions of the Na(+)-H+ exchanger in the brush border and the
basolateral Na(+)-HCO3- cotransporter. The presence of these systems has
been demonstrated for cultured cells; however, their contributions to the
transepithelial movement of acid equivalents has not been confirmed in
monolayers. To examine transepithelial acidification by intact cells,
tubules were grown on membrane filters. Confluent cultures developed a
transepithelial pH gradient within 6 h by decreasing the pH of medium in
the apical chamber (6.66 +/- 0.03) while raising the basolateral pH to 7.40
+/- 0.02. Cells maintained on plastic did not acidify the medium during
this time. Amiloride (10-100 microM) inhibited development of the gradient
only when placed in the top chamber.
4-Acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS; 10-100
microM), which inhibits basolateral Na(+)-HCO3- cotransport, decreased the
gradient only when added to the bottom. These results demonstrate that
cultured proximal tubule cells can develop a transepithelial pH gradient
and that the polarized distribution of the transport systems is maintained
in vitro.
