The Influence of Dietary Cholesterol on 26-Hydroxycholesterol and the Effect of 26-Hydroxycholesterol on the Intracellular Free Calcium Level
Kou, I-Ling
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https://hdl.handle.net/2142/70097
Description
Title
The Influence of Dietary Cholesterol on 26-Hydroxycholesterol and the Effect of 26-Hydroxycholesterol on the Intracellular Free Calcium Level
Author(s)
Kou, I-Ling
Issue Date
1987
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Health Sciences, Nutrition
Abstract
Oxidized derivatives of cholesterol, such as 26-hydroxycholesterol are an enzymatic oxidation product of cholesterol, which have been studied in vivo and in vitro systems. These studies indicated that they affect membrane permeability, cause membrane perturbance, inhibit enzyme activity and cause cellular injury. However, the role of 26-hydroxycholesterol in calcium permeability is still unknown.
The purpose of this study was to investigate the factors influencing serum level of 26-hydroxycholesterol after long-term consumption of cholesterol by animals. It is also to examine the effect of this sterol on intracellular free calcium level. Purified 26-hydroxycholesterol was synthesized from kryptogenin by the Clemmemsen and Wolff-Kishner reduction method. 26-Hydroxycholesterol was also used for fatty acid esters syntheses, and to study its influence on membranes. Tritiated 26-hydroxycholesterol which was synthesized by an enzymatic method, was used to monitor the 26-hydroxycholesterol loss during the procedure. The ester form of 26-hydroxycholesterol was also synthesized, and used to investigate its effects on membranes.
The HPLC method that was developed for the analysis of 26-hydroxycholesterol levels in animal tissues was accurate, efficient, and reproducible for the determination of 26-hydroxycholesterol in plasma. However, it was not suitable for the analysis of other tissues, due to the overlappng of peaks making quantitation difficult.
26-Hydroxycholesterol increased in rabbit plasma but not in rat plasma after cholesterol feeding. The 26-hydroxycholesterol was primarily carried in the VLDL, IDL and LDL fractions in rabbit plasma.
The intracellular free calcium of platelets was monitored by the fluorescent probe, quin 2. 26-Hydroxycholesterol was found to increase the intracellular free calcium level of platelets, after one hour incubation in a 37$\sp\circ$C water bath. There was no influence of cholesterol and the esterified 26-hydroxycholesterol on platelets intracellular free calcium levels. The result suggests that the additional polar group of 26-hydroxycholesterol might be inserted into the membranes and thus caused the membrane to be more leaky to the calcium ions.
This study indicates that the 26-hydroxycholesterol level in the circulation is increased in the rabbits after the consumption of cholesterol. The 26-hydroxycholesterol thus may affect cellular membrane permeability, and may cause the membrane to be more leaky to Ca$\sp{2+}$.
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