Equilibration of Plasma and Adrenal Cholesterol in Man

Borkowski, Abraham; Levin, Sam; Delcroix, Claude; Klastersky, Jean

doi:10.1530/acta.0.061s053

Cited by 5 publications

(7 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From a qualitative point of view and with the exception of the most unsaturated cholesteryl esters (A4) the pattern of the in vitro esterification is comparable to that previously found in vivo (4). Indeed, the specific activities of cholesterol in the various esters are fairly similar to each other, indicating that the distribution of the newly formed cholesteryl esters is similar to that already present before incubation; this is particularly striking for the A1 and A2 cholesteryl esters (essentially oleate and linoleate) which are the most abundant and are found in reversed proportions in plasma (26) and in the adrenal cortex (19).…”

Section: Discussionsupporting

confidence: 82%

“…In vitro synthesis of adrenal cholesterol from acetate-2-'4C. The adrenal glands obtained in the operating room were immediately placed in a solution of Krebs-Ringer-bicarbonate and processed in the cold room as previously described (3,4). The slices of adrenal tissue were then incubated, during 3 hr, at 370C, in a metabolic incubator, under constant agitation and in an atmosphere of 95% oxygen and 5%o carbon dioxide.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Metabolism of adrenal cholesterol in man

Borkowski¹,

Delcroix²,

Levin³

1972

J. Clin. Invest.

View full text Add to dashboard Cite

A B S T R A C T The synthesis of adrenal cholesterol, its esterification and the synthesis of the glucocorticosteroid hormones were studied in vitro on human adrenal tissue.It was found that the synthesis of adrenal cholesterol may normally be small in the zona "fasciculata," particularly when compared with the synthesis of the glucocorticosteroid hormones, that it is several times higher in the zona "reticularis" where esterified cholesterol is less abundant, and that under ACTH stimulation it increases strikingly and proportionally to the degree of esterified adrenal cholesterol depletion.On the other hand, the relative rate of esterification as well as the concentration of free adrenal cholesterol are remarkably stable: they do not differ according to the adrenal zonation and are unaffected by ACTH. Furthermore, from a qualitative point of view, the relative proportions of A1 and A2 cholesteryl esters formed in situ are similar to those anticipated from their relative concentrations, suggesting that the characteristic fatty acid distribution of the adrenal cholesteryl esters results from an in situ esterification rather than from a selective uptake of the plasma cholesteryl esters. Besides, the in vitro esterification reveals a propensity to the formation of the most unsaturated cholesteryl esters.Regarding hydrocortisone and corticosterone, their synthesis tends to be more elevated in the zona "fasciculata." Despite its higher cholesterol concentration the zona "fasciculata" should not therefore be viewed as a

show abstract

Section: Discussionsupporting

confidence: 82%

Section: Methodsmentioning

confidence: 99%

Metabolism of adrenal cholesterol in man

Borkowski¹,

Delcroix²,

Levin³

1972

J. Clin. Invest.

View full text Add to dashboard Cite

show abstract

“…Previous studies in humans (19,20) and rats (21,22) have demonstrated that 80% or more of the cholesterol as a substrate for adrenal steroidogenesis might come from plasma, especially from plasma lipoproteins (23)(24)(25). These reports suggested that cholesterol esters which were used for steroidogenesis were stored as lipid droplets, and that free cholesterol for steroidogenesis was mainly provided by hydrolysis of the deposited cholesterol ester by CEase (3,9,26).…”

Section: Discussionmentioning

confidence: 99%

Studies on Cholesterol Esterase in the Rat Adrenal*

Nishikawa¹,

Mikami²,

Saitō³

et al. 1981

Endocrinology

View full text Add to dashboard Cite

We have investigated the characteristics and properties of cholesterol esterase (CEase) in the rat adrenal to clarify the mechanism of synthesis of free cholesterol from esterified cholesterol. CEase activity was estimated using substrate vesicles which were sonicated mixtures of cholesteryl oleate and phosphatidylcholine (PC). CEase showed two optima at around pH 4.5 and pH 8.25. The acid CEase was found mainly in the lysosomal fraction, and the alkaline CEase was found mainly in the microsomal fraction. Both acid and alkaline CEase activities were markedly enhanced by increasing the concentration of PC, but not by phospholipids. The activities were not increased by the addition of cAMP, ATP, and MgCl2, when the molar ratio of cholesteryl oleate to PC was 1:0.2, but were increased when the molar ratio was 1:2. Thus, it is suggested that free cholesterol for steroidogenesis may be supplied by two different organelles (lysosome and microsome), and that the composition of the substrate complex, such as the ratio of esterified cholesterol to phospholipids, may play a crucial role in the regulation of adrenal CEase. Increases in both acid and alkaline CEase activities were observed in adrenal homogenates prepared from hypophysectomized rats treated with an iv injection of ACTH when the molar ratio of cholesteryl oleate to PC used as a substrate vesicle was 1:0.2, but not when the ratio was 1:2. Therefore, the present observation indicate that activation of CEase by ACTH is dependent on the substrate state, especially that of the cholesterol ester droplet in vivo.

show abstract

“…This represents a new theoretical treatment of data previously obtained in 24 patients undergoing bilateral adrenalectomy for generalized mammary carcinoma (2). Cholesterol4-14C was administered i.v.…”

Section: Methodsmentioning

confidence: 99%

“…The role of free adrenal cholesterol in the structure of the membranes makes it imperative for reasons of structural stability that its concentration be constant. It is indeed remarkable how free adrenal cholesterol varies little despite important variations of the adrenal functional state (2).…”

Section: Parameters Of Adrenal Cholesterol In Control Studiesmentioning

confidence: 99%

Metabolism of adrenal cholesterol in man

Borkowski¹,

Delcroix²,

Levin³

1972

J. Clin. Invest.

View full text Add to dashboard Cite

A B S T R A C T The kinetics of plasma and adrenal cholesteral equilibration were analyzed in patients undergoing bilateral adrenalectomy for generalized mammary carcinoma. A biological model is proposed to help in the understanding of adrenal cholesterol physiology. It comprises two intracellular compartments: (1) A compartment of free adrenal cholesterol which is small (of the order of 17 mg) but turns over very fast; it is renewed approximately 8 times per day: 3 times by the inflow of free plasma cholesterol, and 5 times by the hydrolysis of esterified adrenal cholesterol, the contribution of adrenal cholesterol synthesis appearing to be relatively small. (2) A compartment of esterified adrenal cholesterol which is 20 times larger; it is constantly renewed by in situ esterification and hydrolysis with a daily fractional turnover rate of the order of 0.25. The direct and selective accumulation of plasma cholesteryl esters is practically absent. Only free adrenal cholesterol returns to plasma, mostly after conversion into steroid "hormones."However small the synthesis of adrenal cholesterol may be, it seems more important in the zona "reticularis." On the other hand, the inflow of plasma cholesterol and the turnover of the free adrenal compartment tend to be faster in the zona "fasciculata." The equilibration of plasma and adrenal cholesterol can proceed unmodified under conditions of ACTH suppression.

show abstract

Equilibration of Plasma and Adrenal Cholesterol in Man

Cited by 5 publications

References 0 publications

Metabolism of adrenal cholesterol in man

Metabolism of adrenal cholesterol in man

Studies on Cholesterol Esterase in the Rat Adrenal*

Metabolism of adrenal cholesterol in man

Contact Info

Product

Resources

About