Thrombin induces the rapid formation of inositol bisphosphate and inositol trisphosphate in human platelets.

Human platelets prelabeled with [3H]inositol were exposed to thrombin. The aqueous soluble inositol phosphates were separated by anion exchange column chromatography, paper chromatography or high-performance liquid chromatography, and identified by cochromatography with authentic standard substances. Thrombin immediately induces the rapid formation of inositol 1,4-bisphosphate and inositol 1,4,5-trisphosphate. Accumulation of inositol-1-monophosphate and inositol-2-monophosphate occurs later after a time lag of 10 sec. The results indicate that the phospholipase C induced polyphosphoinositide hydrolysis rather than the phosphatidylinositol hydrolysis is the triggering event for platelet activation, and support the concept of inositol 1,4,5-trisphosphate as putative second messenger.