CHANGES IN INOSITOL 1,4,5-TRISPHOSPHATE MASS IN AGONIST-STIMULATED HUMAN NEUTROPHILS

Changes in the endogenous synthesis of inositol 1,4,5-trisphosphate (IP3) mass have been quantitated in human peripheral neutrophils stimulated with FMLP, LTB4 and PAF using a recently described, highly specific radioreceptor assay. Each agonist induced a concentration-dependent synthesis of IP3 which was detectable within 10 seconds after stimulation. IP3 production was short-lived, returning to basal levels within 90 seconds. The maximal stimulated level of IP3 in response to FMLP and LTB4 was 30-50 pmoles/10(7) neutrophils. PAF was more effective (almost-equal-to 100 pmoles IP3/10(7) neutrophils). The response to FMLP was inhibited by pertussis toxin, but was unaffected by cholera toxin. Pretreatment with cytochalasin B did not enhance IP3 synthesis. These findings are generally consistent with previous studies employing [H-3]myo-inositol-prelabeled cells, and provide one of the first measurements of IP3 synthesis by mass in agonist-stimulated human neutrophils.