| Abstrakt: |
The quantitative extraction, separation, and estimation of brain lipids should include a number of precautions to avoid or limit potential artifacts. It is particularly important to avoid these pitfalls when the objective is to assess the pool size and composition of minor, but metabolically very active, components such as free fatty acids (FFAs) and diacylglycerols (DGs) (Bazan, 1970, 1982, 1983; Bazan et al., 1983, 1985a). The quantitative estimation of these brain lipids poses several problems not found with other lipid classes. For example, if proper care is not taken during brain sampling, FFAs and DGs accumulate (Bazan, 1970; Aveldano and Bazan, 1975a). At the same time, polyphosphoinositides undergo rapid postmortem degradation (Eichberg and Hauser, 1967; Hauser et al., 1971). In addition, the unsaturated components of FFAs and DGs deserve special attention. Although their levels are lowest under resting conditions (Bazan, 1970; Cenedella et al., 1975; Bazan et al., 1983), they show by far the largest increase during brain ischemia or hypoxia (Bazan, 1970; Bazan etal., 1971; Aveldano and Bazan, 1975b; Cenedella et al., 1975) and are subsequently used as precursors for eicosanoids if sufficient oxygen is available. Thus, special care must be taken to avoid artifactual peroxidative changes of highly unsaturated fatty acids. Various methods for the isolation and estimation of these lipids have been described previously (Bazan and Joel, 1970; Bazan and Cellik, 1972; Bazan and Bazan, 1975; Rodriguez de Turco and Bazan, 1977). The main aim of this article is to describe in detail different procedures that are used in our laboratory for the quantitative extraction, separation, and estimation of brain lipid classes. Emphasis is placed on the quantitative extraction and estimation of minor lipids, such as FFAs, DGs, phosphatidic acid, and polyphosphoinositides. These procedures include modifications and improvements of methods described previously, such as the use of quantitative capillary gas-liquid chromatography (GC), solvent systems, and ready-made thinlayer chromatography (TLC) plates from commercial sources to isolate and estimate various lipids from brain and retina [ABSTRACT FROM AUTHOR] |
