INTRACELLULAR PH, CYTOSOLIC CALCIUM-CONCENTRATION AND ELECTRICAL-ACTIVITY IN RINM5F INSULINOMA CELLS

The addition of L-lactate or acetate to RINm5F cells caused a transient intracellular acidification, an increase in [Ca2+](i) and induced electrical activity. The subsequent withdrawal of lactate or acetate resulted in an intracellular alkalinization with no apparent changes in [Ca2+](i) nor electrical activity. Intracellular alkalinization and acidification by application and withdrawal of NH4Cl were both accompanied by transient increases in [Ca2+](i) in the absence of electrical activity. The induction of electrical activity by lactate was associated with the appearence of inward whole cell currents. Changes in intracellular pH may affect [Ca2+](i) though not necessarily by altering plasma membrane potential. The inward currents associated with lactate application may represent an organic anion conductance contributing towards the stimulation of electrical activity by organic acids.