REGULATION OF INTRACELLULAR CHLORIDE CONCENTRATION IN RAT LACTOTROPHS- POSSIBLE ROLE OF MITOCHONDRIA

Increasing evidence is accumulating for the involvement of chloride io ns in the stimulus-secretion coupling of pituitary cells. We show that the mean intracellular chloride concentration [Cl-]i of rat lactotrop h cells maintained in culture is high, close to 60 mM (59.4 mM), using the Cl- sensitive fluorescent probe 6-methoxy-N-(3-sulfopropyl) quino linium (SPQ), coupled with whole-cell patch-clamp recordings. We demon strate that this high level is correlated with the presence of mitocho ndrial stores of Cl- as shown by the release of Cl- in response to var ious metabolic inhibitors, We determine that CCP (50 mu M) induces a m ean [Cl-]i increase of 15.8 +/- 5.8 mM, using combined electrophysiolo gy and microspectrofluorimetry methods, These data strongly suggest th at cell metabolism, including the mitochondrial function, modulate [Cl -]i.