title: Modulation of phosphatidylinositol-4,5-bisphosphate hydrolysis in rat aorta by guanine nucleotides, calcium and magnesium.
abstract: Rat aortic smooth muscle homogenates and membrane preparations contain a phospholipase C which hydrolyzes phosphatidylinositol 4,5-biphosphate (PIP2). We discovered that guanyl-5'yl-imidodiphosphate (Gpp(NH)p) activated the hydrolysis of exogenous PIP2 but not of phosphatidylinositol (PI) in rat aortic membranes. Further, maximal Gpp(NH)p-dependent hydrolysis was dependent on physiological levels of calcium. Also, magnesium inhibited PIP2 hydrolysis and catalyzed the dephosphorylation of PIP2 to phosphatidylinositol-4-phosphate (PIP). The results imply that PIP2 is the primary substrate of the nucleotide-regulated phospholipase C in rat aorta and that calcium and magnesium are physiological regulators of this activity.
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D006165:Guanylyl Imidodiphosphate; D004533:Egtazic Acid; D006160:Guanosine Triphosphate; D010738:Type C Phospholipases; D008274:Magnesium; D002118:Calcium