title: Muscarinic release of inositol trisphosphate without mobilization of calcium in bovine adrenal chromaffin cells.
abstract: Chromaffin cells of bovine adrenal medulla release catecholamines in response to activation of nicotinic ACh receptors which open voltage-sensitive calcium channels. Catecholamine secretion by exocytosis requires an increase in cytosolic free calcium. The cells also possess muscarinic ACh receptors but muscarinic agents do not provoke catecholamine release. Quin-2 studies show that they do not increase cytosolic free Ca2+ concentration, but unlike the nicotinic agents, they cause phosphoinositide hydrolysis. Muscarinic stimulation leads to rapid loss of labelled phosphatidylinositol 4-phosphate and of phosphatidylinositol 4,5-bisphosphate. At the same time there is release of inositol trisphosphate, inositol bisphosphate and inositol phosphate. In a number of other cells inositol trisphosphate may act as a second messenger releasing Ca2+ from storage sites in the endoplasmic reticulum but this is not its function in bovine chromaffin cells.
mesh_terms: D000313:Adrenal Medulla / Q000187:drug effects / Q000378:metabolism*; D000634:Aminoquinolines; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002417:Cattle; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D010277:Parasympathomimetics / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000502:physiology; D013403:Sugar Phosphates / Q000378:metabolism*
chemical_list: D000634:Aminoquinolines; D007295:Inositol Phosphates; D010277:Parasympathomimetics; D010716:Phosphatidylinositols; D010743:Phospholipids; D011976:Receptors, Muscarinic; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; C035739:Quin2; D002118:Calcium