arachidonyltrifluoromethane and mastoparan

A GTP-binding protein (G-protein), termed G-exocytosis (Ge), mediates the effects of calcium ions in the late stages of the adrenocorticotrophin (ACTH) secretory pathway. An activator of Ge, mastoparan, also stimulates phospholipase A(2) and so a comparison of other phospholipase A(2)-activating peptides, melittin and phospholipase A(2)-activating peptide was made with mastoparan to assess whether phospholipase A(2)activation was an important component of Ge-evoked secretion. All three peptides stimulated ACTH secretion in the effective absence of calcium ions from permeabilised cells, actions potentiated by a phospholipase A(2)inhibitor. Ca(2+)-evoked secretion from permeabilised cells was similarly potentiated by a phospholipase A(2) inhibitor. Furthermore, arachidonic acid inhibited Ca(2+)- and Ge-evoked ACTH secretion, an action blocked by the cyclo-oxygenase inhibitor ibuprofen. This study suggests that the products of phospholipase A(2)-generated arachidonic metabolism may exert an inhibitory action on the late post-Ca(2+) stages of the ACTH secretory pathway and that prostaglandins may be the active agents in this capacity.

Topics: Adrenocorticotropic Hormone; Animals; Arachidonic Acid; Arachidonic Acids; Calcium; Cell Membrane Permeability; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Enzyme Activation; Enzyme Inhibitors; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Ibuprofen; Intercellular Signaling Peptides and Proteins; Melitten; Peptides; Phospholipases A; Proteins; Tumor Cells, Cultured; Wasp Venoms