title: Vasopressin stimulates phosphoinositide hydrolysis in LLC-PK1 cells.
abstract: LLC-PK1 cells have been shown to possess vasopressin (VP) receptors (V2 type) that are coupled to adenyl cyclase to generate adenosine 3,5'-cyclic monophosphate (cAMP). To determine whether VP also stimulates phosphoinositide (PI) hydrolysis to generate inositol phosphate (IP) and diacylglycerol (DAG) messenger system in LLC-PK1 cells, we measured the release of IP in LLC-PK1 cells in the absence and presence of various concentrations of VP. In addition, we also determined the effect of an increase in osmolality of the incubation medium on VP-stimulated PI hydrolysis in LLC-PK1 cells. The methods involved the incubation of LLC-PK1 cells with [3H]inositol for its incorporation into membrane PI and the measurement of the release of [3H]IP in the presence of LiCl which prevents dephosphorylation. The osmolality of the incubation media was increased from 300 to 600, 900, and 1,200 mosmol/kgH2O by the addition of NaCl and urea. In an isosmotic incubation medium, VP (10(-8) M) produced a 100% increase in PI hydrolysis in LLC-PK1 cells. The effect was much greater at higher concentrations of the hormone. There was no effect of osmolality in VP-stimulated PI hydrolysis in LLC-PK1 cells up to 600 mosmol/kgH2O, but PI hydrolysis decreased significantly when the osmolality of the incubation medium was increased to 900 or 1,200 mosmol/kgH2O. Our results suggest that in LLC-PK1 cells, VP stimulates PI hydrolysis probably through VP receptors that are coupled to phospholipase C. Furthermore, VP-stimulated PI messenger system in LLC-PK1 cells is influenced by osmolality of the extracellular fluid.
authors.affiliation: Department of Pharmacology, University of Florida, College of Medicine, Gainesville 32610.
authors.forename: L C
authors.initials: LC
authors.lastname: Garg
authors.forename: E
authors.initials: E
authors.lastname: Kapturczak
authors.forename: M
authors.initials: M
authors.lastname: Steiner
authors.forename: M I
authors.initials: MI
authors.lastname: Phillips
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006868:Hydrolysis; D007294:Inositol / Q000378:metabolism; D007700:Kinetics; D008236:Lypressin / Q000494:pharmacology*; D008563:Membrane Lipids / Q000378:metabolism; D009994:Osmolar Concentration; D010716:Phosphatidylinositols / Q000378:metabolism*; D014667:Vasopressins / Q000037:antagonists & inhibitors
chemical_list: D008563:Membrane Lipids; D010716:Phosphatidylinositols; D014667:Vasopressins; D001127:Arginine Vasopressin; D007294:Inositol; D008236:Lypressin