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GTP gamma S loading of endothelial cells stimulates phospholipase C and uncouples ATP receptors.
- Source :
-
The American journal of physiology [Am J Physiol] 1988 Nov; Vol. 255 (5 Pt 1), pp. C667-73. - Publication Year :
- 1988
-
Abstract
- The effects of GTP gamma S, a stable GTP analogue that can activate guanine nucleotide-binding proteins, on phospholipase C activation/calcium mobilization were studied in intact cultured bovine aortic endothelial cells (BAEC). Phosphoinositide metabolism and cytosolic free Ca2+ concentration [( Ca2+]i; fura-2 fluorescence) were studied after the cells were transiently permeabilized, loaded with different guanine nucleotides, and then allowed to reseal and recover. Intracellular GTP gamma S stimulated a dose-dependent [median effective concentration (EC50) 2.5 microM] decrease in basal [3H]phosphoinositide content. Phosphatidylinositol 4,5-bisphosphate, phosphatidylinositol 4-bisphosphate, and phosphatidylinositol levels decreased to 57 +/- 9, 63 +/- 8, and 74 +/- 8% control levels, respectively, in BAEC loaded with approximately 85 microM GTP gamma S. Basal inositol trisphosphate (IP3) and [Ca2+]i were increased in GTP gamma S-loaded BAEC when compared with sham-loaded BAEC. In control BAEC, the purinergic receptor agonist ATP (100 microM) induced rapid increases in [Ca2+]i and IP3. However, BAEC that had been intracellularly loaded with GTP gamma S [median inhibitory constant (IC50) 1 microM] or 5'-guanylyl-imidodiphosphate exhibited decreased calcium mobilization in response to ATP. Ionomycin (calcium ionophore)-releasable pools of calcium were similar in sham- and GTP gamma S-loaded cells, suggesting that total intracellular calcium had not been depleted by the permeabilization protocol. The diminished calcium mobilization in response to ATP was associated with decreases in ATP-stimulated PIP2 hydrolysis and IP3 formation. In addition, GTP gamma S loading did not increase basal levels of cyclic AMP. Intracellular GDP beta S, GDP, or GTP did not inhibit ATP-stimulated increases in [Ca2+]i or IP3.(ABSTRACT TRUNCATED AT 250 WORDS)
- Subjects :
- Animals
Aorta, Thoracic
Cattle
Endothelium, Vascular metabolism
Guanosine 5'-O-(3-Thiotriphosphate)
Guanosine Triphosphate pharmacology
In Vitro Techniques
Stimulation, Chemical
Endothelium, Vascular drug effects
Guanosine Triphosphate analogs & derivatives
Receptors, Purinergic drug effects
Thionucleotides pharmacology
Type C Phospholipases metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0002-9513
- Volume :
- 255
- Issue :
- 5 Pt 1
- Database :
- MEDLINE
- Journal :
- The American journal of physiology
- Publication Type :
- Academic Journal
- Accession number :
- 3056027
- Full Text :
- https://doi.org/10.1152/ajpcell.1988.255.5.C667