Inhibition of phospholipase C-independent exocytotic responses in rat peritoneal mast cells by U73122.

St. Josef Hospital, Ruhr-University of Bochum, Gudrunstr. 56, D-44791 Bochum, Germany.
Regulatory Peptides (Impact Factor: 2.01). 03/2005; 125(1-3):179-84. DOI: 10.1016/j.regpep.2004.08.023
Source: PubMed

ABSTRACT The aminosteroid U73122 has been established as potent, selective, and cell-permeable inhibitor C-type phosphatidylinositol-specific phospholipases (PI-PLCs), and has been used to define a contribution of PI-PLCs as part of exocytotic signalling pathways in rat peritoneal mast cells (RPMCs). However, doubts have been raised regarding its PI-PLC selectivity of action. Therefore, in the present study, U73122 was tested in RPMCs under experimental conditions allowing to elicit exocytosis PI-PLC independently (streptolysin O [SLO]-permeabilised cells; stimulated by GTPgammaS; in the presence of low concentrations of free Ca2+). The release of [3H]5-hydroxytryptamine ([3H]5-HT) from [3H]5-HT-loaded RPMCs served as measure of secretion. U73122 potently inhibited the exocytotic response induced by 10 microM GTPgammaS (Ca2+: 10(-6) M) in permeabilised cells (IC50: 0.6 microM, n=5) in an insurmountable manner. In intact RPMCs, with a nearly equal potency (IC50: 4 microM, n=4), U73122 also inhibited the PI-PLC-dependent exocytotic response induced by concomitant application of nerve growth factor and lyso-phosphatidylserine (NGF/lyso-PS). CONCLUSION: U73122 exerts potent PI-PLC-independent secretostatic effects, limiting its use to define PI-PLC function within exocytotic processes.

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