Regulation Of Intracellular Chloride Concentration In Rat Lactotrope Cells And Its Relation To The Membrane Resting Potential

Rat lactotrope cells in primary culture exhibit physiological properties closely associated with chloride ions (Cl-) homeostasis. In this work, we studied the regulation of intracellular Cl- concentrations ([Cl-](i)) and its relation to the membrane resting potential, using a combination of electrophysiology and spectrofluorimetry. Variations in [Cl-](i) resulting from the patch clamp technique, pH(i), antagonists of Cl--Ca2+-dependent channels, an anion exchanger antagonist, and an antagonist of K+-Cl- cotransport were considered with respect to their involvement in membrane potential. We show that: (i) The patch-pipette does not always impose its Cl- concentration. (ii) In rat lactotrope cells, membrane resting potential is partially determined by [Cl-](i). (iii) Besides ion channel activity, electroneutral ion transports (cotransports such as K+-Cl- and Na+-K+-2Cl(-)) participate actively in maintaining a high [Cl-](i). (iv) Finally, Cl- homeostasis is probably linked to cell energetics.