Regulation of intracellular chloride concentration in rat lactotrophs: possible role of mitochondria

Increasing evidence is accumulating for the involvement of chloride ions in the stimulus-secretion coupling of pituitary cells. We show that the mean intracellular chloride concentration [Cl −]i of rat lactotroph cells maintained in culture is high, close to 60 mM (59.4 mM), using the Cl − sensitive fluorescent probe 6-methoxy- N-(3-sulfopropyl) quinolinium (SPQ), coupled with whole-cell patch-clamp recordings. We demonstrate that this high level is correlated with the presence of mitochondrial stores of Cl − as shown by the release of Cl − in response to various metabolic inhibitors. We determine that CCP (50 μM) induces a mean [Cl −]i increase of 15.8±5.8 mM, using combined electrophysiology and microspectrofluorimetry methods. These data strongly suggest that cell metabolism, including the mitochondrial function, modulate [Cl −]i.