Mass measurement of inositol 1,4,5-trisphosphate and sn-1,2-diacylglycerol in bombesin-stimulated Swiss 3T3 mouse fibroblasts.

Two specific and selective assays were used to measure changes in the mass of Ins(1,4,5)P3 and sn-1,2-diacylglycerol in bombesin-stimulated Swiss 3T3 cells. The results demonstrate that the increase in Ins(1,4,5)P3 was extremely rapid, but transient, returning to basal levels by 30 s. In contrast, the increase in sn-1,2-diacylglycerol was biphasic: the first phase mirrored the transient Ins(1,4,5)P3 response, whereas the second phase was sustained and occurred in the absence of elevated Ins(1,4,5)P3. The possible source of the second phase of diacylglycerol is discussed.