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Cholera toxin modulation of angiotensin II-stimulated inositol phosphate production in cultured vascular smooth muscle cells.
- Source :
-
The Biochemical journal [Biochem J] 1990 Feb 01; Vol. 265 (3), pp. 799-807. - Publication Year :
- 1990
-
Abstract
- Activation of phospholipase C by angiotensin II in vascular smooth muscle has been postulated to be mediated by an unidentified GTP-binding protein (G-protein). Using a permeabilized preparation of myo-[3H]inositol-labelled cultured vascular smooth muscle cells, we examined the ability of a non-hydrolysable analogue of GTP, guanosine 5'-[gamma-thio]triphosphate (GTP[S]), to stimulate inositol phosphate formation. GTP[S] (5 min exposure) stimulated inositol polyphosphate release by up to 3.8-fold in a dose-dependent manner, with an EC50 (concn. producing half-maximal stimulation) of approx. 50 microM. Inositol bisphosphate (IP2) and inositol trisphosphate (IP3) accumulations were also stimulated by NaF (5-20 mM). Furthermore, angiotensin II-induced inositol phosphate formation could be potentiated by a submaximal concentration of GTP[S] (10 microM), and this treatment appeared to interfere with the normal termination mechanism of the initial hormonal signal. The G-protein mediating angiotensin II-stimulated phospholipase C activation was insensitive to pertussis toxin at an exposure time and concentration which were sufficient to completely ADP-ribosylate all available substrate (100 ng/ml, 16 h). In contrast, a similar incubation with cholera toxin markedly inhibited angiotensin II-stimulated IP2 and IP3 release by 67 +/- 6% and 62 +/- 6% respectively. Cholera toxin appeared to inhibit angiotensin II stimulation of phospholipase C by a dual mechanism: it caused a 45% decrease in angiotensin II receptor number, and also inhibited G-protein transduction as assessed by GTP[S]-stimulated IP2 formation. This latter inhibition may be secondary to an increase in cyclic AMP, since it could be simulated by addition of dibutyryl cyclic AMP. Thus angiotensin II-stimulated inositol phosphate formation is cholera-toxin-sensitive, and is mediated by a pertussis-toxin-insensitive G-protein, which may be involved directly in termination of early signal generation.
- Subjects :
- Adenosine Diphosphate Ribose analysis
Animals
Bucladesine pharmacology
Calcium analysis
Cells, Cultured
Depression, Chemical
Electrophoresis, Polyacrylamide Gel
Endothelium, Vascular cytology
Guanosine 5'-O-(3-Thiotriphosphate)
Guanosine Triphosphate analogs & derivatives
Guanosine Triphosphate metabolism
Inositol 1,4,5-Trisphosphate isolation & purification
Rats
Receptors, Angiotensin metabolism
Sodium Fluoride pharmacology
Thionucleotides metabolism
Angiotensin II pharmacology
Cholera Toxin pharmacology
Endothelium, Vascular metabolism
Inositol 1,4,5-Trisphosphate metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0264-6021
- Volume :
- 265
- Issue :
- 3
- Database :
- MEDLINE
- Journal :
- The Biochemical journal
- Publication Type :
- Academic Journal
- Accession number :
- 2154969
- Full Text :
- https://doi.org/10.1042/bj2650799