Arachidonic acid (AA) is generated in the pancreatic islets during glucose stimulation. We investigated whether AA activated extracellular Ca 2+ entry in rat pancreatic β cells via a pathway that was independent of the activation of voltage-gated Ca 2+ channels. The AA triggered [Ca 2+ ] i rise did not involve activation of GPR40 receptors or AA metabolism. When cells were voltage clamped at −70mV, the AA-mediated intracellular Ca 2+ release was accompanied by extracellular Ca 2+ entry. AA accelerated the rate of Mn 2+ quench of indo-1 fluorescence (near the Ca 2+ -independent wavelength of indo-1), reflecting the activation of a Ca 2+ -permeable pathway. The AA-mediated acceleration of Mn 2+ quench was inhibited by La 3+ but not by 2-APB (a blocker of capacitative Ca 2+ entry), suggesting the involvement of arachidonate-regulated Ca 2+ (ARC) channels. Consistent with this, intracellular application of the charged membrane-impermeant analog of AA, arachidonyl-coenzyme A (ACoA) triggered extracellular Ca 2+ entry, as well as the activation of a La 3+ -sensitive small inward current (1.7pA/pF) at −70mV. Our results indicate that the activation of ARC channels by intracellular AA triggers extracellular Ca 2+ entry. This action may contribute to the effects of AA on Ca 2+ signals and insulin secretion in rat β cells.