2.2.5. Determination of lipoprotein oxidation
LDL oxidation is a lipid peroxidation chain reaction driven by free radical intermediates, which is accompanied by characteristic changes of chemical, physiochemical, and biological properties. Therefore, a variety of methods may be used for determining the rate and extent of oxidation in vitro (Puhl et al. 1994) and in vivo (Jialal and Devaraj 1996).
For in vivo LDL oxidation determination, the immunological method for autoantibody to Ox-LDL has been widely used (Jialal and Devaraj 1996), while a recent developed baseline diene conjugation measurement is a promising method for estimating LDL oxidation in vivo (Ahotupa et al. 1998).
The in vitro estimation of LDL oxidation includes measurement of the increase of thiobarbituric acid-reactive substances (TBARS), total lipid hydroperoxides, defined lipid hydroperoxides, hydroxy- and hydroperoxy fatty acids, conjugated dienes (CD), oxysterols, lysophospholipids, aldehydes, fluorescent chromophores, measurement of disappearance of endogenous antioxidants and PUFA, oxygen uptake, and total peroxyl radical trapping potential (TRAP) (Puhl et al. 1994, Valkonen and Kuusi 1997).
A convenient and very frequently used method for continuously monitoring the process of copper-induced LDL oxidation is to measure the conjugated diene formation at 234 nm as a time course in a UV spectrophotometer (Esterbauer et al. 1989).
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