Specificity of inositol trisphosphate-induced calcium release from permeabilized Swiss-mouse 3T3 cells

Abstract

Swiss-mouse 3T3 cells permeabilized with saponin were used to study the specificity of the inositol trisphosphate-induced release of 45Ca2+ from their intracellular stores. Inositol 1,4,5-trisphosphate was the most potent compound studied (dose giving half-maximal effect 0.3 .mu.M). 45Ca2+ was also released by inositol 2,4,5-trisphosphate, glycerophosphoinositol 4,5-bisphosphate and inositol 4,5-bisphosphate, with doses giving half-mximal effect of, respectively, 1.6 .mu.M, 1.6 .mu.M and 20 .mu.M, but it was not released by inositol 1,4-bisphosphate (50 .mu.M). The trans-vicinal phosphates on the 4- and 5-positions are probably essential for the Ca2+-mobilizing effect of inositol trisphosphate, and, in addition, there is a requirement for a phosphate group on the opposite side of the molecule, with a preference for the 1-position.