Metabolism of phosphatidylinositol in plasma membranes and synaptosomes of rat cerebral cortex: A comparison between endogenous vs exogenous substrate pools
- Univ. of Missouri, Columbia (USA)
The metabolism of phosphatidylinositols (PI) labeled with (14C)arachidonic acid within plasma membranes or synaptosomes was compared to the metabolism of PI prelabeled with (14C)arachidonic acid and added exogenously to the same membranes. Incubation of membranes containing the endogenously-labeled PI pool in the presence of Ca2+ resulted in the release of labeled arachidonic acid, as well as a small amount of labeled diacylglycerol. Labeled arachidonic acid was effectively reutilized and returned to the membrane phospholipids in the presence of adenosine triphosphate (ATP), CoA, and lysoPI. Although Ca2+ promoted the release of labeled diacylglycerol from prelabeled plasma membranes, this amount was only 17% of the maximal release, i.e., release in the presence of deoxycholate and Ca2+. This latter condition is known to fully activate the PI-phospholipase C, and incubation of prelabeled plasma membranes resulted in a six-fold increase in labeled diacylglycerols. On the other hand, when exogenously labeled PI were incubated with plasma membranes in the presence of Ca2+, the labeled diacylglycerols released were 59% of that compared to the fully activated condition. The phospholipase C action was calcium-dependent, regardless of whether exogenous or endogenous substrates were used in the incubation. In contrast to plasma membranes, intact synaptosomes had limited ability to metabolize exogenous PI even in the presence of Ca2+, although the activity of phospholipase C was similar to that in the plasma membranes when assayed in the presence of deoxycholate and Ca2+. These results suggest that discrete pools of PI are present in plasma membranes, and that the pool associated with the acyltransferase is apparently not readily accessible to hydrolysis by phospholipase C.
- OSTI ID:
- 7063696
- Journal Information:
- Lipids; (USA), Journal Name: Lipids; (USA) Vol. 25:5; ISSN LPDSA; ISSN 0024-4201
- Country of Publication:
- United States
- Language:
- English
Similar Records
Ca/sup 2 +/-dependent and Ca/sup 2 +/-independent pathways for release of arachidonic acid from phosphatidylinositol in endothelial cells
Phosphoinositide phosphorylation and hydrolysis in pancreatic islet cell membrane
Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ALCOHOLS
ALKALINE EARTH METAL COMPOUNDS
ANIMAL CELLS
ANIMALS
ARACHIDONIC ACID
ATP
BODY
BRAIN
CALCIUM COMPOUNDS
CARBON 14 COMPOUNDS
CARBOXYLESTERASES
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CELL MEMBRANES
CENTRAL NERVOUS SYSTEM
CEREBRAL CORTEX
CEREBRUM
CHELATING AGENTS
CHROMATOGRAPHY
COENZYMES
COMPARATIVE EVALUATIONS
EGTA
ENZYMES
ESTERASES
ESTERS
GAS CHROMATOGRAPHY
GLYCOLS
HYDROLASES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LIPASES
LIPIDS
LIPOPROTEINS
MAMMALS
MEMBRANES
METABOLISM
MONOCARBOXYLIC ACIDS
NERVE CELLS
NERVOUS SYSTEM
NUCLEOTIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANS
PHOSPHOLIPIDS
PROTEINS
RATS
RODENTS
SEPARATION PROCESSES
SOMATIC CELLS
SUBSTRATES
TRACER TECHNIQUES
VERTEBRATES