title: Phosphorylation of phosphoinositides in human platelets.
abstract: 32P-labelling of phosphatidylinositol (PI), PI-4-monophosphate (PIP), PI-4,5-bisphosphate (PIP2) and phosphatidic acid (PA) in 32P-labelled intact human platelets was investigated in the presence of various agents which alter intracellular level of cAMP or Ca2+. Addition of dibutyryl cAMP to intact platelets pre- or pulse labelled with 32P resulted in increased 32P-labelling of PIP and in concomitant decreased 32P-labelling of PI without affecting that of PIP2 or PA. Similar changes were observed in intact platelets treated by prostaglandin I2 (PGI2) or a new low Km phosphodiesterase inhibitor (DN-9693). When intracellular Ca2+ was chelated by loading quin 2-AM to intact platelets, 32P-labelling of PIP was significantly increased in a dose related manner. From these observations it was concluded that PI kinase is activated by elevation of cAMP or chelation of Ca2+ in intact platelets.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000634:Aminoquinolines / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D000242:Cyclic AMP / Q000502:physiology; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D011464:Epoprostenol / Q000494:pharmacology; D006801:Humans; D010712:Phosphatidic Acids / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols / Q000097:blood* / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010766:Phosphorylation; D011799:Quinazolines / Q000494:pharmacology
chemical_list: D000634:Aminoquinolines; D010712:Phosphatidic Acids; D018129:Phosphatidylinositol Phosphates; D010716:Phosphatidylinositols; D010761:Phosphorus Radioisotopes; D011799:Quinazolines; C037178:phosphatidylinositol 4-phosphate; C016276:8-bromocyclic GMP; D003994:Bucladesine; C035738:Quin2-acetoxymethyl ester; C049662:1,5-dihydro-7-(1-piperidinyl)-imidazo(2,1-b)quinazolin-2(3H)-one; D011464:Epoprostenol; D000242:Cyclic AMP; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D006152:Cyclic GMP; D002118:Calcium