CHOLESTEROL

From Big Medical Encyclopedia

CHOLESTEROL (Greek chole bile + stereos firm; a synonym cholesterol) —

Z-R-gidroksikholest-5-en, C27H460, the representative of sterols, most important in the biological relation. Cholesterol is a source of education in an organism of mammal bile acids (see), corticosteroids (see), sex hormones (see), D3 vitamin (see Calciferols.) thus, fiziol. function of cholesterol is extremely diverse. Allocate for cholesterol one of leading roles in development of atherosclerosis (see), according to the modern point of view hyper cholesterol a miya (see) treats leaders etiol. to factors of its development. However correlation between the content of cholesterol in blood and degree of manifestation of atherosclerosis is not always found in the person. In pathology of the person the steady hypercholesterolemia is usually connected with the long disturbance of cholesteric exchange (see) including which is genetically caused. Strengthening of cholesterol in blood is usually observed at a diabetes mellitus, a hypothyroidism, gout, obesity, an idiopathic hypertensia, at nek-ry diseases of a liver, an acute disorder of cerebral circulation, etc. However genesis of a hypercholesterolemia at all these patol. states it is not identical. The lowered content of cholesterol is noted at a row inf. diseases, acute and hron. diseases of intestines, a hyperthyroidism, the expressed heart failure with stagnation of blood in a liver, etc. (see the Hypochilesterinemia).

Cholesterol was described in 1789 by the fr. chemist of A. F. Fou-rcroy as the main compound component of gallstones of the person. In 1816 other fr. chemist Shev-rel (M. of E. Chevreul) for the first time called open Furkrua connection cholesterol. The structure of cholesterol was finalized in the 30th 20 century, then also its full chemical synthesis was carried out.

Pier. the weight (weight) of cholesterol makes 386,66; its molecule consists of four cycles, rigidly connected among themselves and forming a cyclopentanperhydrophenanthrene kernel, and aliphatic appreciate at the 17th carbon atom (C17), the possessing small mobility. In the provision C3 of a molecule of cholesterol there is a hydroxylic group, and in situation C5 — C6 a double bond. All six-carbon cycles of cholesterol are in a configuration of a chair and in a trans-joint, among themselves. Total length of a molecule of cholesterol of 2,2 nanometers, surface area apprx. 3,8 nm2.


cholesterol

From anhydrous solvents cholesterol crystallizes in the form of colourless needles, and from water alcohol — in the form of pearl plates (monohydrate of cholesterol); / °pl

149,5 — 150 °, relative density of d '

8 7

4 1,052, specific rotation [a]D — 39 ° (in chloroform). Cholesterol is water-insoluble (at 20 ° in 100 ml of water only 80 — 150 mkg of cholesterol are dissolved), however it is rather easily dissolved in acetone, alcohol, ether and other organic solvents. We will well dissolve cholesterol in animal and seed fats (oils), and also in mix of polar and non-polar organic solvents.

From chemical properties of cholesterol important biol. its ability to form esters with to-tami matters. The most part of ethers of cholesterol in a human body and other mammals is formed by the higher fatty acids (see) containing

16 — 20 carbon atoms in the chain. The hydroxylic group in a molecule of cholesterol can be oxidized in a ketogroup-pa that occurs, e.g., at formation of steroid hormones (see). Thanks to mobility of hydrogen atom at C7 oxygenated products of cholesterol are easily formed: 7-gidroksi-and 7-ketokholeste-riny. One of them 7-a-gidroksikho-lesterin is the major intermediate product on the way of oxidation of cholesterol in bilious to - you in a liver.

Other important chemical property of cholesterol which is widely used for its analytical definition is its ability to form intensively painted products at interaction with strong to-tami (see Acids and the bases) in non-aqueous solvents: with a chamois to - that in acetic anhydride or in mix acetic to - that is chloroform (see Libermann — Burkhar - yes reaction), with a chamois to - that in chloroform (Salkovsky's reaction), with zinc chloride and chloride acetyl in chloroform (Chu-chayeva reaction), with ferric chloride and a chamois to - that in acetic to - those (reaction of Lip-shyuttsa). The painted products both cholesterol, and its ethers, as well as other sterols containing in 5 — the 6th situation forms a double bond. Feature of cholesterol is its ability to education slightly soluble whom tleks with various to-tami, napr, oxalic, trichloroacetic, and inorganic salts — Calcium chloratum, lithium chloride and especially with half-yen antibiotics (see) and vegetable saponins (see). The complex formation of cholesterol at interaction with half-yen antibiotics is the cornerstone of action of the last on the yeast and drozhzhepodobny organisms containing in the cover sterols (see). Formation of a complex with digitoninokhm is used for separate definition of free (not esterified) and esterified cholesterol: this complex forms only free cholesterol.

According to the chemical analysis, is in a body of the adult apprx. 140 g of cholesterol (about 0,2% of body weight); according to radio - isotope researches, the content of cholesterol is much higher (200 — 350 g).

Separate bodies and tissues of the person contain the following amounts of cholesterol (in mg on 1 g of crude fabric): bark of adrenal glands — 100; a brain and nervous tissue — 20; a vascular wall — 5; a liver, kidneys, a spleen, marrow, skin — 3; connecting fabric — 2; a skeletal muscle — 1. Neeterifitsi-rovanny cholesterol preferential is a part of cellular membranes and myelin covers. Tissues of a brain, bile and erythrocytes contain only neeterifitsiro-bathing cholesterol; skeletal muscles contain 93% of not esterified and 7% of esterified cholesterol, and adrenal glands, on the contrary, contain 83% of esterified and 17% of not esterified cholesterol. In a blood plasma of the person about two thirds of cholesterol are etherified.

Each cell contains cholesterol in an organism of mammals and needs it for keeping fit (so iaz. function of cellular «skeleton»). Being a part of cellular membranes, not esterified cholesterol together with phospholipids (see Phosphatides) provides selective permeability of a cellular membrane for the substances which are entering a cell and coming out it. Together with phospholipids cholesterol regulates activity of the membrane and connected enzymes by change of viscosity of a membrane and modification of secondary structure of enzymes.

Cholesterol forms complexes with nek-ry proteins, especially with those, molecules to-rykh contain a large number of the remains of arginine (see) and a lysine (see). In the presence of phospholipids ability of cholesterol to form complexes with proteins increases. With nek-ry phospholipids, napr, with lecithin (see), cholesterol directly forms complexes, to-rye in an aqueous medium give micellar solutions; during the processing of such solutions ultrasound liposomes turn out. It is characteristic that in an animal organism everywhere where cholesterol meets, to it phospholipids accompany. Ethers of cholesterol are in a cell and can be considered as its reserve form. Their hydrolysis is as required carried out with the participation of a lysosomic holesterinesteraza (see).

Content of cholesterol in a blood plasma of the person depends on age: most low it at newborns (65 — 70 mg! 100 ml), by 1 year of life concentration of cholesterol increase more than twice and reach approximately 150lgg/100 ml, by 7 — 8 years the content of cholesterol increases in a blood plasma only on 10 — 15 mg! 100 ml, remaining constants up to 13 — 14 years then decreases a little. From 18 — 20 years there occurs the gradual, but steady strengthening of cholesterol in a blood plasma to a nek-swarm of a constant continuing up to 50 years at men and up to 60 — 65 years at women. In the advanced countries of Europe and America, and also in Australia average concentration of cholesterol in a blood plasma of men of 40 — 60 years makes 205 — 220 mg / 100 ml, and. in a blood plasma of women of the same age of 195 — 235 mg / '100 ml.

Content of cholesterol in erythrocytes makes 120 — 140 mg!

100 ml and at healthy people do not depend on its concentration in a blood plasma.

It is established that in a blood plasma of the person and animals all cholesterol is in structure of lipopro-teidny complexes (see Lipoproteids), with the help to-rykh and its transport is carried out. The adult about 67 — 70% of cholesterol of a blood plasma has in structure of lipoproteids of the low density (LPNP), 9 — 10% — as a part of lipoproteids of very low density (LPONP) and 20 — 24% — as a part of lipoproteids of the high density (LPVG1). Similar distribution is characteristic also of the animals susceptible to development of atherosclerosis — monkeys, pigs, rabbits, Guinea pigs, pigeons, etc. On the contrary, at the animals steady against development of atherosclerosis — dogs, cats, gophers, minks, polar foxes, raccoons, etc., the most part of cholesterol of a blood plasma is in LPVP possessing anti-atherogenous action.

Other extracellular liquids contain the following amounts of cholesterol (mg / 100 ml): bile —

390; plasma of sperm — 80; a secret of a prostate — 80; a lymph — 25; milk — 20; synovial fluid — 7; saliva — 5; cerebrospinal liquid — 0,4; urine — 0,2.

For quantitative definition of cholesterol in plasma (serum) of blood use the methods based on the stated above staining reactions (over 400 options of such methods are offered). The methods based on Libermann's reaction — the Drill hard and Lipshyutts's reactions are most often used. Methods of definition of cholesterol are subdivided on one-stage — without preliminary extraction of cholesterol from plasma (serum) of blood — and multistage, including extraction of cholesterol, and in a number of methods saponification (see) ethers of cholesterol, sedimentation of not esterified cholesterol digitonin and then carrying out staining reaction. The accelerated method of the Fisher (see the Fisher a method), and also a method Wordly — Goods, based on education by cholesterol of the painted product in solution ice acetic to - you and acetic anhydride belongs to one-stage methods at addition sulfuric and sulphosalicylic to - t. One-stage methods are simple performed by, but yield the overestimated results. From multistage methods in a wedge, practice the method Abel and sotr is widely applied. (see Abel a method), the including

ii r e d in and r and t e l N about e e to with t r and and r about in and the N and e

cholesterol from plasma (serum) petroleum ether, Levchenko and Zngelgardt's methods — Smirnova, at to-rykh cholesterol extracts - with I chloroform, Pokrovsky's micromethod (see Pokrovsky micromethods) providing use for extraction of spirtoefirny mix. Treat this group of methods also Rappoport's method — Engelberg and Grigo's method. Simultaneous definition of the general and free cholesterol is carried out by means of multistage methods with use of digitonin for sedimentation of free cholesterol (see Balakhovsko-go a method). Automatic methods of definition of cholesterol on devices Technicon, Abbot, etc. are based on education by cholesterol of the painted products too.

Apply also enzymatic method based on oxidation of cholesterol in the presence of a holesterinok-sidaza to definition of cholesterol (holesteroloksidaza; KF

1.1.3.6) and determination of amount of the formed hydrogen peroxide, and also gazokhromatografichesky definition (see the Chromatography). Effective division of cholesterol and its ethers is reached by means of hromatografichesky methods, in particular a chromatography in a thin coat.

In general definition of cholesterol by various methods yields ambiguous results. The method Abel and sotr is arbitration.

In clinic became accepted to calculate the size of the relation of cholesterol of atherogenous lipoproteids to cholesterol of anti-atherogenous lipoproteids. One of such relations — so-called cholesteric coefficient of an aterogennost — is calculated on the basis of definition of concentration of the general cholesterol and cholesterol of lipoproteids of high density:

x — X-lpvp x-lpvp ’

where X — concentration of cholesterol. H-LPVP — concentration of cholesterol of lipoproteids of high density. This relation is ideal at newborns (no more than 1), at persons 20 — 30 years its size fluctuates from 2 to 2,8, at persons 30 years without wedge are more senior, symptoms of atherosclerosis it is in limits 3 — 3,5, and at persons with coronary heart disease exceeds 4, reaching quite often 5 — 6 and above. This coefficient as an indicator of development of atherosclerosis is more sensitive, than cholesterol-le-tsitinovy an indicator (the attitude of concentration of cholesterol towards concentration of lecithin in a blood plasma), to-ry at one time was widely applied in clinic.

Bibliography: Biochemical methods of a research in clinic, under the editorship of A. A. Pokrovsky, sa 18, M., 1969; F and z e r Lv and

F and z e r M. Steroids, the lane with English, M., 1964; Chevreul M. E. Note sur le sucre de diabetes, Ann. Chim. (Paris), t. 95, p. 319, 1815; My ant N. The biology of cholesterol and related steroids, L., 1981, A. H. Klimov, D. V. Ioffe.

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