文章基本信息

标题：Hepatic 7alpha-hydroxylation of cholesterol in ascorbate-deficient and ascorbate-supplemented guinea pigs.
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作者：I Björkhem ; A Kallner
期刊名称：JLR Papers In Press
印刷版ISSN：0022-2275
电子版ISSN：1539-7262
出版年度：1976
卷号：17
期号：4
页码：360-365
语种：English
出版社：American Society for Biochemistry and Molecular Biology
摘要：Cholesterol 7alpha-hydroxylase activity was assayed in liver microsomes from guinea pigs supplemented with ascorbate and from guinea pigs in a state of ascorbate deficiency. A mass fragmentographic method was used by which the 7alpha-hydroxylation of endogenous cholesterol could be measured. The 7alpha-hydroxylation was markedly reduced in the ascorbate-deficient animals as compared to animals treated with ascorbate. Addition of ascorbate to the incubations did not increase this activity. 11- and 12-Hydroxylation of laurate as well as 25- and 26-hydroxylation of 5beta-cholestane-3alpha, 7alpha-diol were not significantly affected by the ascorbate status of animals. In the presence of excess NADPH-cytochrome P-450 reductase and a phospholipid, partially purified cytochrome P-450 from the microsomal fraction of liver of an ascorbate-deficient guinea pig had a much lower capacity to 7alpha-hydroxylate [4-14C]cholesterol than a corresponding system containing cytochrome P-450 from liver of an ascorbate-supplemented guinea pig. It is suggested that ascorbate affects the synthesis or breakdown of the 7alpha-hydroxylating system, in particular the cytochrome P-450 component.