RETINOLUM (synonym axerophthol) — fat-soluble vitamin, one of vitamer of vitamin A; in medicine derivatives of Retinolum use as medicinal prophylactics.
Biol. activity of vitamin A in different degree its vitamer have: Retinolum, a retinal, retinoic to - that and degidroretinol.
River — one of first identified vitamins (see), it was opened in 1915 by Mack-E. V. McCollum and by Davis (M. of Davis), to-rye established that growth of experimental animal (rats) depends on substance, soluble in organic solvents. They called this substance vitamin A. Later from a liver of fishes the vitamer of vitamin A — vitamin A was allocated 2 (degidroretinol).
Pure R. forms large crystals of light yellow color. It exists in a trance - and cis-forms (see. Isomerism ). The maximum of absorption at the wavelength of 325 nanometers, t°pl 63 — 64 is characteristic of trans-isomer P. °; for cis-isomer at most of absorption is at the wavelength of 328 nanometers, and t°pl 59 — 60 °. Retinolum is steady against effect of alkalis, but collapses in acid medium. In solutions P. easily is oxidized on air therefore the characteristic maximum of absorption in the UF-spectral range disappears. The oxidized R. loses vitamin activity. R.'s oxidation can be prevented with the help antioxidants (see) or inhibitors of free radical processes (see. Radicals free ). For this purpose use and - tocopherol (vitamin E) or synthetic antioxidants.
The role of vitamin A in an organism
the Role of vitamin A in an organism is connected with processes of reproduction and growth, maintenance of the immune status, function of sight (photoreception), a differentiation of epithelial fabrics. Value of vitamin A for a normal differentiation and development of epithelial fabric (including a spermatogenic epithelium and a placenta), perhaps, is caused by its participation in the form of a retinilfosfat in transfer of the remains of sugars (a fukoza, mannose) at synthesis of glycoproteins of cellular membranes. The same mechanism can be the cornerstone of participation of vitamin A in functioning of immune system.
The ruble participates in the mechanism sight (see). Derivative Retinolum — the retinal — is chromophore of rhodopsins at all animals (see. Rhodopsins , Rodopsin ) except for nek-ry fishes, at to-rykh chromophore is degndroretinal.
Vitamer of vitamin A — retinoic to - that is has only partial activity of a vitakhmin And. It supports a differentiation of an epithelium and growth of experimental animals, but is not active concerning processes of reproduction and photoreception.
In an organism of animals (except predators) R. is synthesized in a wall of intestines from p-carotene (see. Karotin ). Transformation of carotene into vitamin A in intestines depends on receipt with food of fats and proteins, and also on sufficient receipt in intestines of bile and an active lipase (KF 18.104.22.168). Vitamins E and With and other natural antioxidants protect vitamin A from destruction in intestines. R. by blood after formation of a complex with special retinolsvyazyvayushchy protein of a blood plasma is transported. In fabrics P. is in a type of ethers palmitic and others fat to - t, in such look it collects also in a liver. The river — one of the few vitamins, to-ry can be deposited in an organism in large numbers.
Biol. activity of vitamin A and its contents in foodstuff express in retinolovy equivalents (micrograms or milligrams of Retinolum) or in the international units (ME): 1 ME vitamins A would correspond a yole. activities of 0,3 mkg of Retinolum or 0,344 mkg of a retinilatsetat. The daily need for vitamin A for the adult of 1,0 mg, for pregnant women and the feeding women of 1,25 — 1,5 mg, for children and teenagers from 0,4 to 1,0 mg.
The main source of vitamin A are plants rich with carotene: carrots, a dogrose, sweet cherry, pumpkin, sheet green vegetables — spinach, green cabbage; it is a lot of carotene in butter, milk, yolks of eggs. The liver of animals, including a liver of marine mammals and fishes is richest with vitamin A; the liver of cattle contains apprx. 500 ME vitamins A in 1 g, a liver of a pig — apprx. 200 ME in 1 g. In fish oil (cod-liver oil) the content of vitamin A is not less than 350 ME in 1 g.
At R.'s arrival in an organism in the doses significantly exceeding fiziol. requirement, development of a hypervitaminosis is possible And (see. Hypervitaminoses ). At the same time note a headache, vomiting, dizziness, an acrimony, a peeling of skin and a hair loss. There are data that in the concentration exceeding physiological R. has the damaging effect on cellular and subcellular membranes.
Rubles quantitatively define spektrofotometrichesk (see. Bessey methods ) and on staining reaction Cara — the Price: in chloroformic SbCl solution 3 Retinolum is painted in cornflower blue color (a maximum of absorption at 620 nanometers). Big distribution was gained by a flyuorimetrichesky method of definition of Retinolum (see. Flyuorimetriya ).
As the first manifestation of a lack of R. of an organism serves disturbance of twilight sight — hemeralopia (see), i.e. disturbance of ability of an eye to adapt to darkness, a so-called night blindness. Then can develop xerophthalmia (see). Further sometimes there is a necrosis of a cornea — a keratomalacia (see. Eye, pathology ) and panophthalmia (see). Besides, keratinization of skin is observed (see. Hyperkeratosis ) and mucous membranes, especially mucous membranes of a mouth, lower parts of respiratory tracts and a gullet, tissue of endocrine glands, including sexual is damaged, sensitivity to inf increases. to diseases. Oxygen consumption increases in tissues of experimental animals with avitaminosis And, the content of phosphatides increases and the content of cholesterol decreases. Development of a so-called secondary hypovitaminosis And, its absorption caused by disturbance in intestines is possible.
See also Vitamin deficiency .
Retinolum as drug
as treatment-and-prophylactic means in medicine use Retinolum acetate (Retinoli acetas) and Retinolum palmitate (Retinoli palmitas), to-rye treat group vitamin drugs (see). Retinolum palmitate is quicker and more stoutly soaked up in a small bowel, than Retinolum acetate that is connected with the increased ability of Retinolum of palmitate to emulsification.
Retinolum acetate represents white or pale yellow crystals, water-insoluble, soluble in oils and alcohol; it loses activity under the influence of oxygen of air and on light. Retinolum palmitate represents homogeneous mass of light yellow color, low solubility in water; it melts at a temperature close to 26 °, turning into a transparent oily liquid.
Drugs P. are used at hypo - and avitamonous And states; at diseases of eyes — a pigmental retinitis (see. Tapetoretinalny dystrophies ), xerophthalmia (see), hemeralopias, superficial keratitis (see), defeat corneas (see), conjunctivitis (see), pyodermas (see), eczematic defeat century (see); at infectious diseases and their complications — dysentery (see), measles (see), pneumonia (see), bronchitis (see), etc.; at diseases of skin — ichthyosis (see), a follicular dyskeratosis (see. to Darya disease ), senile keratosis (see), a tuberculosis cutis (see. Tuberculosis extra pulmonary ), psoriasis (see), nek-ry forms eczemas (see); at diseases of the digestive system — hron. gastritises (see), inflammatory and erosive cankers intestines (see), cirrhoses of a liver (see) etc.
Drugs are appointed inside right after food; Retinolum acetate is appointed also intramusculary. Solutions of Retinolum of acetate for injections before introduction warm up to body temperature.
Daily preventive doses of vitamin A for adults 5000 ME, for pregnant women 6600 ME, for the feeding women 8250 ME; for children till 1 year 1650 ME, from 1 year to 6 years 3300 ME, of 7 years 5000 ME. In the conditions of Far North preventive doses of vitamin A for pregnant women and the feeding women, and also for children shall be increased by 50%.
At hypovitaminoses or avitaminosis And moderately severe daily medical doses for adults make 33 000 ME; for children from 1000 to 5000 ME depending on age. At diseases of skin of 50 000 — 100 000 ME in days for adults and on 5000 — 10 000 — 20 000 ME for children.
The highest single doses of vitamin A shall not exceed 50 000 ME for adults and 5000 ME for children.
Drugs P., especially at treatment of children and at purpose of high doses, it is necessary to apply under observation of the doctor as at overdoses there can be conditions of a hypervitaminosis, and also be observed exacerbations of cholelithiasis and hron. pancreatitis. At intramuscular injections of Retinolum of acetate local morbidity and sometimes formation of infiltrates are possible.
Forms of release: a dragee on 3300 ME (for the preventive purposes), tablets of Retinolum of acetate on 33 000 ME; solution of Retinolum of acetate in oil on 5000, 33 000 and 100 000 capsular ME; 3,44%, 6,88% or 8,6% the solutions of Retinolum of acetate in oil containing in 1 ml respectively 100 000, 200 000 and 250000 ME; solutions of Retinolum of acetate in oil on 25 000, 50 000 or 100 000 MB in 1 ml in ampoules for injections; 5,5%, 11,0% or 46,5% the solutions of Retinolum of palmitate in oil supporting respectively 100 000, 200 000 and 300 000 ME in 1 ml; 1,651% apply the solution of Retinolum of palmitate containing in 1 ml apprx. 33 000 ME in pediatrics to complex therapy rickets (see), respiratory viral diseases (see), proceeding against the background of exudative diathesis, acute and hron. bronchopulmonary diseases, hypotrophies (see) and kollagenoz (see. Collagenic diseases ). Retinolum acetate and Retinolum palmitate are also a part of various polyvitaminic drugs.
Store drugs of vitamin A in bottles from dark glass in the cool, protected from light place.
Bibliography: Vitamins, under the editorship of M. I. Smirnov, page 46, M., 1974; Clinical pharmacology, under the editorship of V. V. Zakusov, page 353, M., 1978; Halmuradova., Fenny V. N. and H and about in e c R. V. Transport of fat-soluble vitamins, Kiev, 1980; Experimental vitaminology, under the editorship of Yu. M. Ostrovsky, page 132, etc., Minsk, 1979.
M. A. Ostrovsky; V. M. Avakumov (pharm.).