Expression of Na(+)-H+ exchange and ATP-dependent proton extrusion in growing rat IMCD cells
| Autor: | D. C. Boxer, Robert Stanton, Joseph Seifter |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
DNA Replication
Male Sodium-Hydrogen Exchangers Physiology ATPase Sodium chemistry.chemical_element Acid–base homeostasis Ammonium Chloride Amiloride Adenosine Triphosphate Renal medulla medicine Animals Secretion Cells Cultured Kidney Kidney Medulla biology Chemistry Rats Inbred Strains Cell Biology Hydrogen-Ion Concentration Rats Kinetics Proton-Translocating ATPases medicine.anatomical_structure Biochemistry Cell culture Ethylmaleimide biology.protein Biophysics Protons Carrier Proteins Intracellular Thymidine |
| Zdroj: | The American journal of physiology. 258(3 Pt 1) |
| ISSN: | 0002-9513 |
| Popis: | As the last step of urinary acidification, the inner medullary collecting duct (IMCD) is thought to secrete protons into the tubular lumens by means of a H(+)-translocating adenosinetriphosphatase (H(+)-ATPase). However, recent studies have also shown the existence of Na(+)-H+ exchange activity in IMCD cells. Although the physiological function of the antiporter in IMCD cells is unknown, activation of Na(+)-H+ exchange in other cell-culture systems has been suggested to be closely associated with the process of cell growth. Thus presence of Na(+)-H+ exchange may relate to the growth phase of these cells. To examine intracellular pH (pHi) regulation in growing IMCD cells, we studied proton transport by Na(+)-dependent and Na(+)-independent mechanisms by microfluorimetry using the pHi-sensitive dye 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein acetoxymethyl ester (BCECF/AM). Actively growing cells, defined by [3H]thymidine incorporations, demonstrated an amiloride-sensitive Na(+)-dependent pHi recovery after an acid load. No pHi recovery was evident in the absence of Na+, indicating the importance of Na(+)-H+ exchange for pHi recovery. However, when evaluated in quiescent cells, Na(+)-dependent pHi recovery appeared to be diminished. Instead, a Na(+)-independent pHi recovery which was inhibitable by ATP depletion and by 1 mM N-ethylmaleimide was present, suggesting function of a H(+)-ATPase. These findings indicate that Na(+)-dependent proton extrusion activity (Na(+)-H+ exchange) but not Na(+)-independent proton extrusion activity is expressed during the rapid growth phase of IMCD cells, whereas the more quiescent cells express Na(+)-independent ATP-dependent proton extrusion activity and a possibly less active Na(+)-H+ exchanger. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|