Guanine nucleotides stimulate phosphoinositide breakdown in permeabilized platelets

Conference · Thu May 01 00:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:7108687

Culty, M; Haslam, R J

Human platelets were preincubated with myo-(/sup 3/H)inositol in the presence of Mn/sup 2 +/, permeabilized by high voltage electric discharges and isolated by gel filtration. After equilibration with ATP, Ca/sup 2 +/ buffers and 0-100 ..mu..M GTP..gamma..S at 0/sup 0/C, the platelets were incubated for 0 to 5 min at 25/sup 0/C. Incubation alone led to a Ca/sup 2 +/-independent conversion of (/sup 3/H)phosphatidylinositol to (/sup 3/H)phosphatidylinositol 4-phosphate (PIP). In addition, GTP..gamma..S (100 ..mu..M) caused a 30-40% loss of (/sup 3/H)phosphatidylinositol 4,5-bisphosphate (PIP/sub 2/) in the presence of 0.1-1.0 ..mu..M Ca/sup 2 +//sub free/. This was fully accounted for by the progressive accumulation of inositol monophosphate (IP) and inositol bisphosphate (IP/sub 2/) in a ratio of 3:1. After 5 min, GTP..gamma..S had increased IP by >8-fold and IP/sub 2/ by >4-fold. Only traces of inositol trisphosphate (IP/sub 3/) were detected. Li/sup +/ (10 mM) increased IP/sub 2/ accumulation at the expense of IP, indicating conversion of the former to the latter, but did not increase IP/sub 3/. Unlabelled IP/sub 3/ (400 ..mu..M) reduced the intracellular degradation of 14 ..mu..M (/sup 32/P)IP/sub 3/ added to permeabilized platelets by 55% but did not decrease (/sup 3/H)IP/sub 2/ formation or increase (/sup 3/H)IP/sub 3/ in GTP..gamma..S-stimulated platelets. Thrombin (2 units/ml), in the presence of 10 ..mu..M GTP, stimulated the formation of inositol phosphates in a manner qualitatively similar to GTP..gamma..S. These results suggest that, in platelets, a guanine nucleotide-binding protein can activate breakdown of PIP/sub 2/ to IP/sub 2/ and diacylglycerol by a pathway that does not involve IP/sub 3/ formation.

• Research Organization: McMaster Univ., Hamilton, Ontario
• OSTI ID: 7108687
• Report Number(s): CONF-8606151-
• Journal Information: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINES
ANIMALS
AROMATICS
ATP
AZAARENES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BIOLOGICAL PATHWAYS
BLOOD
BLOOD CELLS
BLOOD PLATELETS
BODY FLUIDS
CARBOHYDRATES
CATIONS
CHARGED PARTICLES
DAYS LIVING RADIOISOTOPES
ESTERS
GUANINE
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INOSITOL
INOSITOLS
IONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LIGHT NUCLEI
LIPIDS
MAMMALS
MAN
MANGANESE COMPOUNDS
MATERIALS
METABOLISM
MONOSACCHARIDES
NUCLEI
NUCLEOTIDES
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PERMEABILITY
PHOSPHOLIPIDS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PRIMATES
PURINES
RADIOISOTOPES
REACTION KINETICS
SACCHARIDES
TRACER TECHNIQUES
TRANSITION ELEMENT COMPOUNDS
TRITIUM COMPOUNDS
VERTEBRATES