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 mu M) 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.