Enzymes involved in cholesterol homeostasis in outer vs inner cortices of the guinea pig adrenal
Adrenocortical cells require cholesterol for steroid hormone synthesis. Intracellular free cholesterol levels are maintained by the actions of three key enzymes: HMG CoA reductase, a rate limiting enzyme of cholesterol biosynthesis, acyl CoA:cholesterol acyltransferase (ACAT), which esterifies cholesterol to fatty acids, and cholesterol ester hydrolase (CEH), which releases stored cholesterol by clearing the ester bond. The guinea pig adrenal cortex, which can be separated into a lipid-rich outer zone and a lipid-poor inner zone, provides a good model in which to determine whether the morphological differences in these regions correlate with functional distinctions in enzymes of cholesterol homeostasis. These studies have shown that there are great differences in these enzymes in the outer and inner zones of the guinea pig adrenal cortex. The cholesterol-rich outer zone possesses greater activities of ACAT and CEH than the inner zone, and, in untreated animals, these enzymes are nearly maximally stimulated. Both zones had substantial levels of HMG CoA reductase, as measured by enzyme assay and ELISA, and these levels increased following ACTH stimulation. However, only the outer zone incorporated /sup 14/C-acetate into steroids and cholesterol to any great degree in vitro, and only in this zone was incorporation increased following incubation of cultures with ACTH. The discrepancies between HMG CoA reductase levels and /sup 14/C-acetate incorporation in the inner zone indicate that cholesterol synthesis must be regulated differently in this zone.
- Research Organization:
- New York Univ., NY (USA)
- OSTI ID:
- 6075292
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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CHOLESTEROL
BIOSYNTHESIS
HYDROLASES
ENZYME ACTIVITY
OXIDOREDUCTASES
TRANSFERASES
ACETATES
ADRENAL GLANDS
BIOLOGICAL MODELS
CARBON 14 COMPOUNDS
ENZYME IMMUNOASSAY
GUINEA PIGS
HOMEOSTASIS
TRACER TECHNIQUES
ANIMALS
BODY
CARBOXYLIC ACID SALTS
ENDOCRINE GLANDS
ENZYMES
GLANDS
HYDROXY COMPOUNDS
IMMUNOASSAY
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
ORGANIC COMPOUNDS
ORGANS
RODENTS
STEROIDS
STEROLS
SYNTHESIS
VERTEBRATES
550201* - Biochemistry- Tracer Techniques