PMID- 18840665
OWN - NLM
STAT- MEDLINE
DCOM- 20081211
LR  - 20131121
IS  - 0022-0949 (Print)
IS  - 0022-0949 (Linking)
VI  - 211
IP  - Pt 20
DP  - 2008 Oct
TI  - Ionic determinants of pH of acidic compartments under hypertonic conditions in 
      trout hepatocytes.
PG  - 3306-14
LID - 10.1242/jeb.020776 [doi]
AB  - Exposure of trout hepatocytes to hypertonicity induced a decrease in acridine 
      orange (AO) fluorescence, indicating a corresponding decrease in pH inside the 
      lumen of acidic compartments (pH(L)). Pre-exposure of cells to the specific 
      V-ATPase inhibitor bafilomycin A1 (0.3 micromol l(-1)) increased AO fluorescence 
      - unmasking H(+) leaks under steady-state conditions - and partially removed the 
      hypertonicity-induced pH(L) decrease. The sustainability of the luminal 
      acidification, but not the acidification itself, appeared to depend on a low K(+) 
      and a high Cl(-) conductance under hypertonic conditions. Increasing K(+) 
      conductance using the specific ionophore valinomycin (10 micromol l(-1)) or 
      removal of extracellular Cl(-) after an instant drop in AO fluorescence resulted 
      in a reversal of luminal acidity. The alkalinization measured under hypertonic 
      conditions in the absence of Cl(-) was largely attenuated when cells were bathed 
      in HCO(3)(-)-free medium, signifying the possible presence of Cl(-)/HCO(3)(-) 
      exchange. Under steady-state conditions, while a slight and brief pH(L) increase 
      was measured upon exposure of cells to valinomycin, Cl(-) removal, unexpectedly, 
      induced a decrease in pH(L), indicating a role for extracellular Cl(-) in 
      limiting luminal acidification. This was confirmed by the substantial pH(L) 
      decrease measured upon exposure of cells to the anion exchanger inhibitor SITS 
      (0.5 mmol l(-1)). Furthermore, hypertonicity-induced acidification was still 
      noticeable in the presence of SITS. On the other hand, the hypertonicity-induced 
      acidification was significantly reduced in the absence of extracellular Na(+) or 
      Ca(2+). However, BAPTA-AM induced an increase in steady-state pH(L) that was 
      independent of V-ATPase inhibition. Moreover, the BAPTA-induced alkalinization 
      was still apparent after depletion of intracellular Ca(2+) using the Ca(2+) 
      ionophore A23187 in Ca(2+)-free medium. We conclude that pH(L) of trout 
      hepatocytes is sensitive to hypertonicity and ionic determinants of 
      hypertonicity. Thus, changes in pH(L) should be considered when studying pH 
      adaptations to hypertonic stress.
FAU - Ahmed, Khaled H
AU  - Ahmed KH
AD  - Institut fur Zoologie and Center of Molecular Biosciences, Leopold Franzens 
      Universitat Innsbruck, Innsbruck, Austria.
FAU - Pelster, Bernd
AU  - Pelster B
LA  - eng
PT  - Journal Article
PL  - England
TA  - J Exp Biol
JT  - The Journal of experimental biology
JID - 0243705
RN  - 0 (Acids)
RN  - 0 (Bicarbonates)
RN  - 0 (Chlorides)
RN  - 0 (Hypertonic Solutions)
RN  - 0 (Ions)
RN  - 9NEZ333N27 (Sodium)
RN  - EC 3.6.3.14 (Proton-Translocating ATPases)
RN  - F30N4O6XVV (Acridine Orange)
RN  - RWP5GA015D (Potassium)
RN  - SY7Q814VUP (Calcium)
SB  - IM
MH  - Acids/metabolism
MH  - Acridine Orange/metabolism
MH  - Animals
MH  - Bicarbonates/metabolism
MH  - Calcium/metabolism
MH  - Cell Compartmentation
MH  - Cells, Cultured
MH  - Chlorides/metabolism
MH  - Hepatocytes/*metabolism
MH  - Hydrogen-Ion Concentration
MH  - Hypertonic Solutions/chemistry/metabolism
MH  - Ions/chemistry/metabolism
MH  - Potassium/metabolism
MH  - Proton-Translocating ATPases/metabolism
MH  - Sodium/metabolism
MH  - Trout/*metabolism
EDAT- 2008/10/09 09:00
MHDA- 2008/12/17 09:00
CRDT- 2008/10/09 09:00
PHST- 2008/10/09 09:00 [pubmed]
PHST- 2008/12/17 09:00 [medline]
PHST- 2008/10/09 09:00 [entrez]
AID - 211/20/3306 [pii]
AID - 10.1242/jeb.020776 [doi]
PST - ppublish
SO  - J Exp Biol. 2008 Oct;211(Pt 20):3306-14. doi: 10.1242/jeb.020776.