AJP - Renal Physiology, Vol 261, Issue 6 963-F974, Copyright © 1991 by American Physiological Society

ARTICLES

Localization and regulation of acid-base secretory currents from individual epithelial cells

C. Scheffey, A. M. Shipley and J. H. Durham
Department of Biological Sciences, Columbia University, New York, New York 10027.

The turtle urinary bladder is composed of different epithelial cell types that are suspected to separately produce electrogenic acid and alkali excretion. We measured the electrical currents produced by individual cells, scanning a two-dimensional vibrating probe over the luminal surface of the bladder. Acidification (outward current) was produced by the type of epithelial cell rich in carbonic anhydrase (CA cells). The measured currents of these cells quantitatively accounted for the total epithelial acidification current. When alkali secretion was induced by adenosine 3',5'-cyclic monophosphate and acidification was inhibited (by luminal pH 4), we measured inward currents localized to a small number of epithelial cells in four bladders but found no localization in the other seven treated bladders. When alkali secretion was localized and induced without inhibiting acidification, we found both cells producing inward current and cells producing outward current, which demonstrated that the two transport functions can occur simultaneously. We conclude that net acid-base secretion can be determined by regulating the transport rates of separate cells.

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