Ins(1,2,3,4)-P4 is one of the many InsP isomers that could act as small, soluble second messengers in the transmission of cellular signals.{8672,8344,13727} Ins(1,2,3,4)-P4 exhibits agonist activity at the Ins(1,4,5)-P3 receptor expressed in CHO cells where it induces Ca2+ mobilization with an ED50 value of 18.1 μM, making it nearly 180-fold less effective than Ins(1,4,5)-P3 in the same assay.{5630}