Cholesterol dynamics involving esterification and hydrolysis in rat adrenal tissue divided into the zona fasciculata and reticularis (the decapsulated gland) and the zona glomerulosa (the capsular gland) have been studied. Estimation of esterifying activity was based on the radioactivity of the cholesterol ester formed during incubation with palmitate-l-14 C. The activity of esterase was measured by the radioactivity of fatty acid hydrolyzed from cholesteryl-palmitate-l-14 C during incubation.Both activities of esterification and hydrolysis were significantly higher in the decapsulated gland than in the capsular. ACTH treatment in vivo stimulated cholesterol hydrolysis and inhibited cholesterol esterification in the decapsulated gland, while no apparent changes were observed in the capsular gland. The decapsulated gland may be more active than the capsular gland in cholesterol mobilization which involves intracellular transfer and availability of cholesterol ester. These are mediated by stimulation of cholesterol esterase/ inhibiting cholesterol esterifying systems during ACTH-stimulated steroidogenesis and contribute to differences in the steroidogenic response to ACTH between the two zones. {Endocrinology 90: 808, 1972)

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Abstract-Studieson the zonal function of CAMP-binding protein (regulatory pro tein) and CAMP-dependent protein kinases in bovine adrenal glands have been made. Partially purified CAMP-binding protein from bovine adrenal gland divided into three zones, the capsular (zona glomerulosa), the decapsulated (zona fasciculata and reticularis) and the medulla gland was found in microsomal and cytosol fractions.

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