Na+/H+ exchange is responsible for intracellular pH regulation in insulin-secreting HIT-T15 cells.
The addition of glucose to suspensions of HIT-T15 insulinoma cells caused a small, transient acidification followed by a gradual, progressive alkalinisation, as assessed by the fluorescent pH-sensitive dye 2',7'-biscarboxyethyl-5'-(6')-carboxyfluorescein (BCECF). Treatment of cells with acetate or lactate produced an immediate, marked acidification followed by recovery and a subsequent alkalinisation. In contrast, addition of NH4Cl caused a rapid rise in intracellular pH (pHi) and recovery to resting values. In cells where Na+/H+ exchange was inhibited, either with amiloride or by omission of Na+ from the medium, glucose caused a progressive acidification, whilst recovery from acetate- or lactate-induced acidification was prevented. Under sodium-free conditions, recovery from acidification could be initiated by addition of Na+. Inhibition of HCO3-/Cl- exchange by pretreatment with 4,4'-diisothiocyanatostilbene 2,2'-disulphonic acid (DIDS), or by omission of HCO3- or Cl- from the medium did not affect any of the changes in pHi elicited by the above agents. It is concluded that the principal mechanism responsible for pHi regulation in HIT-T15 cells is the Na+/H+ antiporter and that the HCO3-/Cl- exchange systems make little, if any, contribution.
Trebilcock
R
R
Department of Medicine, University of Manchester, U.K.
Lynch
A
A
Tomlinson
S
S
Best
L
L
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000085:Acetates / Q000494:pharmacology; D007516:Adenoma, Islet Cell / Q000378:metabolism*; D000643:Ammonium Chloride / Q000494:pharmacology; D001639:Bicarbonates / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma / Q000378:metabolism*; D007773:Lactates / Q000494:pharmacology; D019344:Lactic Acid; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers; D014407:Tumor Cells, Cultured
D000085:Acetates; D001639:Bicarbonates; D002352:Carrier Proteins; D002712:Chlorides; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007328:Insulin; D007773:Lactates; D017923:Sodium-Hydrogen Exchangers; D000643:Ammonium Chloride; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D019344:Lactic Acid; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid