Lipids of human adrenals

Substrate and inhibitor specificity of the cholesterol oxidase in bovine adrenal cortex

1. Cholesteryl 3beta-sulphate is oxidized in vitro by preparations of bovine adrenal-cortex mitochondria to pregnenolone sulphate and isocaproic acid (4-methyl-pentanoic acid) without hydrolysis of the ester linkage. 2. Free cholesterol is the preferred substrate for adrenal-cortex cholesterol oxidase; the apparent K(m) for cholesteryl sulphate is 500mum and for free cholesterol 50mum under the same conditions. 3. Cholesteryl 3beta-acetate is hydrolysed by bovine adrenal-cortex mitochondria in vitro to free cholesterol, which is subsequently oxidized to more polar steroids and isocaproic acid. Evidence was obtained that other cholesterol esters behave similarly. Cholesterol esters may thus act as precursors of steroid hormones. 4. Cholest-4-en-3-one is only poorly oxidized to isocaproic acid and more polar steroids and thus is probably not a significant precursor of steroid hormones. 5. Cholesteryl esters inhibit the oxidation of cholesterol competitively (K(i) for cholesteryl phosphate 28mum, for cholesteryl sulphate 110mum, for cholesteryl acetate 65mum) but pregnenolone esters do not inhibit this system. 6. Pregnenolone and 20alpha-hydroxycholesterol (both metabolites of cholesterol in this system) inhibit the oxidation of cholesterol non-competitively. K(i) for pregnenolone is 130mum and K(i) for 20alpha-hydroxycholesterol is 17mum. 7. 25-Oxo-27-norcholesterol inhibits cholesterol oxidation non-competitively (K(i)16mum). A number of other Delta(5)-3beta-hydroxy steroids inhibit cholesterol oxidation and evidence was obtained that the 3beta-hydroxyl group was necessary for inhibitory activity. 8. Pregnenolone, 20alpha-hydroxycholesterol and 25-oxo-27-norcholesterol inhibit oxidation of cholesteryl sulphate by this system but their sulphates do not. 9. 3beta-Hydroxychol-5-enoic acid, 3alpha-hydroxy-5beta-cholanic acid and 3beta-hydroxy-22,23-bisnorchol-5-enoic acid stimulated formation of isocaproic acid from cholesterol. 10. No evidence was obtained that phosphorylation or sulphation are obligatory steps in cholesterol oxidation by adrenal-cortex mitochondria. 11. The cholesteryl 3beta-sulphate sulphatase of bovine adrenal cortex was found mostly in the microsomal fraction and was inhibited by inorganic phosphate.

Abnormal n-nonacosane storage in humans: detection by gas chromatography/mass spectrometry of tissue extracts

We report a case of n-nonacosane storage disease, which went undiagnosed until the death of a 55-year-old farmer. Clinical, histological, and biochemical features are discussed. n-Nonacosane storage was identified by gas chromatographic-mass spectrometric analysis of different tissue extracts, n-nonacosane concentration reaching 1.2 mg g-1 of lung tissue and 0.32 mg g-1 of liver tissue. It was possible to rule out a work-induced intoxication, and n-nonacosane storage appeared to be accounted for by a lifelong, heavy consumption of unpeeled apples and Brussels sprouts.

Cholesteryl myristate conformation in liquid crystalline mesophases determined by neutron scattering

The possible involvement of cholesteryl ester states in the development and persistence of atherosclerosis and the transport and storage of cholesteryl esters has led to questions concerning the organization and conformation of cholesteryl ester molecules in both pure phases and membranes. The experiments we report here were designed to measure the distance between the center of mass of the fatty acyl terminal methyl group and the center of mass of the three-carbon branched terminus of the cholesterol moiety at the opposite end of the molecule. The distance obtained is thus a gauge of cholesteryl ester conformation through the conformational range from a completely extended conformation to a U-shaped conformation. Neutron scattering experiments on partially deuterated samples of pure cholesteryl myristate in the crystalline, smectic, cholesteric, and isotropic phases indicate that the molecule is extended in each of these states. A discussion of specific molecular models consistent with these results and extension of these conclusions to other cholesteryl esters is included.

Distribution of cholesteryl esters and other lipids in subcellular fractions of the adrenal gland of the pig

Total lipids from whole pig adrenal glands as well as from their mitochondria, microsomes, liposomes, and cell sap were extracted and fractionated first into neutral lipids and phospholipids. The highest percentage of neutral lipids was found in the cell sap, and the lowest in the microsomal fraction. Neutral lipids were subfractionated into cholesteryl esters, free cholesterol, triglycerides, and free fatty acids. Cholesteryl esters were distributed throughout the liposomes. Free fatty acids represented a substantial part of cell sap lipids, but were present also in the mitochondria, microsomes, and liposomes. Fatty acids of all fractions were analyzed by gas liquid chromatography. Free fatty acids and cholesteryl ester fatty acids from all cellular fractions were similar in composition and were characterized by considerable quantities of linoleic and arachidonic acid. Triglycerides were characterized by an increased percentage of palmitic and a low content of arachidonic acid. Phosphatidyl choline, phosphatidyl ethanolamine, diphosphatidyl glycerol, and sphingomyelin plus phosphatidyl inositol were isolated from the lipids by preparative thin layer chromatography, and their fatty acids analyzed by gas liquid chromatography. Phosphatidyl choline and phosphatidyl ethanolamine from mitochondria, microsomes, and cell sap were very similar in respect of their fatty acid composition. Sphingomyelin plus phosphatidyl inositol was characterized by a high content of C22:2omega6. Diphosphatidyl glycerol was present in mitochondria and in the cell sap.

Metabolism of adrenal cholesterol in man. I. In vivo studies

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. In one patient with Cushing's disease the size of the two adrenal compartments was clearly increased but their equilibration with plasma cholesterol proceeded normally. In another patient the kinetics of hydrocortisone corresponded to those of free adrenal cholesterol in the control studies.

Genetic variation of cholesterol ester content in mouse adrenals

Total cholesterol concentrations in muscle, liver, and plasma do not differ significantly between adult male C57BL/10J and DBA/2J mice. In the adrenal glands of these two strains, of their hybrids, and of AC mice, concentrations of free cholesterol vary by 5 percent. Adrenals from C57 mice, however, contain six times as much esterified cholesterol as adrenals from AC or DBA mice. The intermediate concentrations of cholesterol esters in F(1) hybrids suggest that the difference in this measure is inherited additively. The finding of variation in adrenal cholesterol within a species is useful for the further study of the role of cholesterol in steroidogenesis by means of genetic analysis.