The turtle bladder epithelial cell layer possesses the acetazolamide sensitive functions of electrogenic acidification and cAMP-dependent electrogenic alkalinization. Both of these occur independently from a third process of electrogenic Na-reabsorption. The epithelial cell layer is composed of two basic cell types: granular (G) cells, which contain large intracytoplasmic granules and comprise nearly 80% of the total epithelial cell population; and carbonic anhydrase rich (CA) cells, which are less numerous, and contain abundant carbonic anhydrase activity. The facts that the acid-base transport processes are sensitive to acetazolamide, and that the CA cells contain acetazolamide-sensitive carbonic anhydrase activity, leads to the conclusion that the CA cells are the source of those processes. The independence of those processes from Na-reabsorption leads to the additional conclusion that Na-reabsorption may be produced only by the G cells. By directing the impalement of apical membranes of either G or CA cells with potential sensing microelectrodes, it is planned to determine the cell type responsible for each of these three processes. In a second approach, it will be determined if in the living tissue, changes in acid-base transport result in concomitant morphological changes in epithelial cell morphology. The localization of the cell type responsible for the acid-base and Na-reabsorptive functions, and the determination of transmembrane electrical characteristics of acid-base transport, will provide new insights into how these processes arise and are regulated in both this tissue and perhaps in the mammalian nephron.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Unknown (R23)
Project #
5R23DK035754-03
Application #
3447379
Study Section
Physiology Study Section (PHY)
Project Start
1985-07-01
Project End
1988-12-31
Budget Start
1987-07-01
Budget End
1988-12-31
Support Year
3
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Mount Sinai School of Medicine
Department
Type
Schools of Medicine
DUNS #
City
New York
State
NY
Country
United States
Zip Code
10029
Scheffey, C; Shipley, A M; Durham, J H (1991) Localization and regulation of acid-base secretory currents from individual epithelial cells. Am J Physiol 261:F963-74