Enzymes involved in cholesterol homeostasis in outer vs inner cortices of the guinea pig adrenal

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6075292

Brody, R I

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
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ACETATES
ADRENAL GLANDS
ANIMALS
BIOLOGICAL MODELS
BIOSYNTHESIS
BODY
CARBON 14 COMPOUNDS
CARBOXYLIC ACID SALTS
CHOLESTEROL
ENDOCRINE GLANDS
ENZYME ACTIVITY
ENZYME IMMUNOASSAY
ENZYMES
GLANDS
GUINEA PIGS
HOMEOSTASIS
HYDROLASES
HYDROXY COMPOUNDS
IMMUNOASSAY
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
MAMMALS
ORGANIC COMPOUNDS
ORGANS
OXIDOREDUCTASES
RODENTS
STEROIDS
STEROLS
SYNTHESIS
TRACER TECHNIQUES
TRANSFERASES
VERTEBRATES