The oxidation behavior of cholesterol and the relationship between cholesterol and non-cholesterol lipids in oxidation processes were studied in a bovine red blood cell membrane system (RBC Mb). RBC Mb was prepared with a process of hemolysis and hypotonic washing. After preparation, the RBC Mb suspensions were subjected to oxidation treatments of $\rm H\sb2O\sb2$-Fe, UV (254 nm, 312 nm, and 365 nm), and $\gamma$-irradiation. After the treatments, lipids were extracted, and cholesterol, cholesterol oxides and fatty acids were analyzed with GC and GC-MS. Of all the oxidation products, 7-keto-cholesterol was found to be the major oxidation product of cholesterol. Other oxidation products, to a less extent, were 7-hydroxylcholesterol, $\alpha$- and $\beta$-epoxycholesterol, etc. Oxidative destruction of cholesterol was detected together with the destruction of unsaturated and saturated fatty acids, although the destruction rates were different. Model studies indicated that cholesterol and fatty acids in the suspension of RBC Mb lipid extracts were much more susceptible to oxidative destruction than the cholesterol and fatty acids in the native RBC membranes. UV studies showed the complexity of cholesterol behavior in response to UV lights. Although the destruction of solid crystalline cholesterol at 312 nm UV went much faster than that at 254 nm and 365 nm, the fastest cholesterol destruction in RBC Mb aqueous suspensions occurred at 365 nm UV, which was the least powerful of the 3 wavelengths for solid crystalline cholesterol destruction. For 7-keto-cholesterol, the most destructive wavelength was 254 nm. In $\gamma$-irradiation study, there was no distinctive radiolytic product detected in this study. Contrasted with UV and $\rm H\sb2O\sb2$-Fe treatments, the destruction of cholesterol with $\gamma$-irradiation gave rise to far less production of cholesterol oxides which were detectable with the GC-MS procedures.
| Identifer | oai:union.ndltd.org:UMASS/oai:scholarworks.umass.edu:dissertations-8923 |
| Date | 01 January 1994 |
| Creators | Zhu, Zhengrong |
| Publisher | ScholarWorks@UMass Amherst |
| Source Sets | University of Massachusetts, Amherst |
| Language | English |
| Detected Language | English |
| Type | text |
| Source | Doctoral Dissertations Available from Proquest |
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