ABSTRACT: Previous studies have shown that adenophostin A is a potent initiator of the activation of SOCs (store-operated Ca2+ channels) in rat hepatocytes, and have suggested that, of the two subtypes of Ins(1,4,5)P3 receptor predominantly present in rat hepatocytes [Ins(1,4,5)P3R1 (type I receptor) and Ins(1,4,5)P3R2 (type II receptor)], Ins(1,4,5)P3R1s are required for SOC activation. We compared the abilities of Ins(1,4,6)P3 [with higher apparent affinity for Ins(1,4,5)P3R1] and Ins(1,3,6)P3 and Ins(1,2,4,5)P4 [with higher apparent affinities for Ins(1,4,5)P3R2] to activate SOCs. The Ins(1,4,5)P3 analogues were microinjected into single cells together with fura 2, and dose-response curves for the activation of Ca2+ inflow and Ca2+ release from intracellular stores obtained for each analogue. The
