Language
English
Publication Date
12-25-1975
Journal
Journal of Alzheimer's Disease
DOI
10.1177/13872877251378478
PMID
41066226
PMCID
PMC12614396
PubMedCentral® Posted Date
10-9-2025
PubMedCentral® Full Text Version
Post-print
Abstract
We describe a method for measuring the release of fatty acids from endogenous substrates of human platelet homogenates and membranes. The method depends on the availability of lipids whose fatty acids are odd-chained and therefore suitable as internal reference compounds that, at the time of lipid extraction, can be added to an incubation to permit subsequent quantification of the content of free fatty acids or fatty acids esterified to specific lipids. We found four types of lipolytic activities in human platelets. In homogenates at pH 4.0 a triglyceride lipase operated as shown by the synchrony of triglyceride degradation and release of glycerol and those fatty acids that are the predominant constituents of triglycerides. However, enough arachidonic acid was released at this pH level to suggest some phospholipid breakdown, since triglycerides hold relatively small amounts of this acid. With membranous preparations, in the alkaline pH range there were two peaks of fatty acid release with accompanying degradation of phospholipids. At pH 8.5, where release of the saturated acids, palmitic and stearic, predominated, their sum was 3.5 times that of arachidonic acid. At pH 9.5 the release of palmitic and stearic acids was only slightly below their peak values; however, the release of arachidonic acid nearly equaled the sum of the saturated acids. Linoleic acid was not released in representative amounts by those reactions that released arachidonic acid, despite the overwhelming propensity of both to be esterified at the 2-position of phospholipids. Pertinently, the choline phospholipids are linoleic-rich and the non-choline phospholipids linoleic-poor, while both have a generous endowment of arachidonic acid. With this in mind, we raise the possibility that the phospholipase A2 of human platelets is an endoenzyme because of its tendency to act on those phospholipids that are thought to comprise the inner layer of the cell membrane.
Keywords
Blood Platelets, Calcium, Cell Membrane, Cholesterol Esters, Edetic Acid, Fatty Acids, Nonesterified, Humans, Hydrogen-Ion Concentration, Kinetics, Phospholipids, Triglycerides
Published Open-Access
yes
Recommended Citation
A Derksen and P Cohen, "Patterns of Fatty Acid Release From Endogenous Substrates by Human Platelet Homogenates and Membranes" (1975). Faculty and Staff Publications. 4497.
https://digitalcommons.library.tmc.edu/baylor_docs/4497