title: Vasopressin stimulation of vanadate-sensitive Na+ transport by liver plasma membrane vesicles. Evidence for regulation via phospholipase C and protein kinase C activities.
abstract: The rate of vanadate-sensitive 22Na+ uptake by isolated liver membrane vesicles, reflecting transport by Na+/K(+)-ATPase, was measured to study the role played by phospholipase C and protein kinase C in the regulation of this process by vasopressin. Na+ uptake was enhanced 2-3-fold by 100 nM [Arg8]vasopressin and the hormone effect was mimicked by 0.1 microM inositol 1,4,5-trisphosphate as well as by 1.0 microM myo-inositol. The stimulation by vasopressin was potentiated by phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis (5-10 mU/ml). No effect of the bacterial enzyme was observed in the absence of the hormone. Phorbol myristate acetate (0.5-1 microM) suppressed the stimulation by vasopressin but had no effect in the absence of the hormone. High concentrations of bacterial phosphatidylinositol-specific phospholipase C (50-100 mU/ml) also antagonized the hormone stimulation. Staurosporine (50-100 nM) prevented the antagonistic effect of bacterial phospholipase C (50 mU/ml) and EGTA (1 mM) partially protected the hormonal stimulation in the presence of phorbol myristate acetate. Our results suggest that the stimulatory effect of vasopressin on Na+ transport is mediated by phospholipase C and products derived from the inositol moiety of membrane phospholipids. Membrane-associated protein kinase C appears to be at least partially responsible for the desensitization to stimulation by vasopressin.
authors.affiliation: Department of Biochemistry, University of Basel, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Piec
authors.forename: A
authors.initials: A
authors.lastname: Jakob
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D008099:Liver / Q000378:metabolism*; D008297:Male; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism*; D010738:Type C Phospholipases / Q000502:physiology*; D014638:Vanadates / Q000494:pharmacology*; D014667:Vasopressins / Q000494:pharmacology*
chemical_list: D014667:Vasopressins; D014638:Vanadates; D004533:Egtazic Acid; D012964:Sodium; D011493:Protein Kinase C; D010738:Type C Phospholipases