4-acetamido-4--isothiocyanatostilbene-2-2--disulfonic-acid and Insulinoma

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.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Acetates; Adenoma, Islet Cell; Ammonium Chloride; Bicarbonates; Carrier Proteins; Chlorides; Fluoresceins; Fluorescent Dyes; Hydrogen-Ion Concentration; Insulin; Insulin Secretion; Insulinoma; Lactates; Lactic Acid; Pancreatic Neoplasms; Sodium-Hydrogen Exchangers; Tumor Cells, Cultured