BILIOUS PIGMENTS — the excreted substances representing end products of disintegration of hemoglobin and other derivative porphyrines. They make 15 — 20% of dry weight of bile of the person; keeping of some of them serves as additional diagnostic test at a number of diseases in blood serum and urine.
On the chemical structure they are related to the protoporphyrin IX making a structural basis gem (see. Gemoglobin ). In their molecule there are four pyrrol groups too, but not in the form of the closed structure, and in the form of an open chain. Besides, in. the quantity and location of double bonds is a little changed the item, but in side chains there are same radicals: methyl (M), vinyl (V), rest of propionic acid (R) and ethyl (E).
In 1937 Fischer (N. of Fischer) showed proximity of tetrapyrrole structure gem and bilirubin. It was found out later that. items are formed by hl. obr. from the hemoglobin released at an erythrocytolysis in reticuloendothelial system (RES).
Formation of bilious pigments
Views of ways of transformation of hemoglobin in. items are contradictory.
Most of researchers considers that there is not one, and several ways of transformation of hemoglobin in. item.
That which goes through a mode of formation of choleglobin is most known (the scheme 1, a way And).
In a molecule of hemoglobin as a result of effect of specific enzymes, generally microsomal NADF-zavisimoy gemoksigenaza (KF 184.108.40.206), there is an oxidizing splitting alpha metinovogo the bridge gem connecting two adjacent pyrrol groups. Ring structure gem is broken off, at the same time one carbon atom in the form of monocarbon monoxide (CO) separates. This process is localized in microsomes and CO is oppressed. The system of a gemoksigenaza as believe, belongs besides to type, as the fermental system causing oxidation another of the connections neutralized by a liver and excreted: some toxins, medicinal substances and endogenous steroids.
As a result of splitting of the metinovy bridge choleglobin — ferriferous green a porphyria with an open pyrrol chain, keeping complex communication with a globin is formed. Further from it the globin, and then and iron is chipped off, and it turns into a green bilious pigment biliverdin. Choleglobin can be received by in vitro by oxidation of hemoglobin in the presence of ascorbic to - you.
The microsomal gemoksigenaza is among so-called oxygenases with the mixed function. It catalyzes oxidizing splitting gem as as a part of hemoproteins, not connected with protein. Enzyme needs presence of NADF and R-450 cytochrome. Widespread idea that splitting gem is caused by soluble fermental system of gems — alpha metiniloksigenaza for a cut the most specific substrate is a complex hemoglobin — gaptoglobin, was not confirmed.
Other metabolic way of education. the item begins with eliminating of a globin from a molecule of hemoglobin (the scheme 1, a way of B). At the same time zhelezoporfirinovy connection — hematin which then is exposed to oxidation with a rupture of the metinovy bridge is formed and, losing iron, turns into biliverdin. Hematin (or. related to it ferriprotoporfirin) is considered as the first intermediate product in this process. According to most of researchers, iron is necessary for oxidizing splitting of the metinovy bridge. Protoporphyrin IX at mammals can turn in. the item only through a mode of formation gem or hematin. Proceeding from data on exchangeability gem between molecules of hemoglobin and about existence in a liver of a pool free gem, some authors consider the second way of a catabolism gem at animals and the person prevailing.
Released at education. the item monocarbon monoxide (in the ratio 1 mol on 1 mol of a pigment) is found in blood of animals and the person in the form of carboxyhaemoglobin, quantitative definition to-rogo is used for establishment of intensity of formation of bilirubin in an organism. The chipped-off iron in a look ferritin (see) and hemosiderin remains in cells to be used in new synthesis of hemoglobin, and partly passes into blood.
Biliverdin is not emitted from cells of reticuloendothelial system (RES) in blood and does not come to a liver though the liver and has ability to turn this pigment into bilirubin. In cells of RES biliverdin under the influence of NADF-zavisimoy enzyme of a biliverdinreduktaza (KF 220.127.116.11) is recovered. The central part of a molecule of biliverdin joins two hydrogen atoms, and the double bond moves therefore biliverdin turns into a red-yellow pigment — the bilirubin which is at mammals the basic. the item (see. Bilirubin ). It passes into blood and is transported to a liver.
There are also other sources of education. item. Falls to their share apprx. 10 — 30% of all excreted bilirubin. Treat such sources gems or his organic predecessors who are formed in cells of RES, but are not used for synthesis of hemoglobin or the hemoglobin which is breaking up in cells in the course of maturing of erythrocytes. Both of these sources are connected with an erythrogenesis. Essential value has also a pool free gem in a liver. At last, source. the item to a certain extent is a catabolism of other zhelezoporfirinovy (gemsoderzhashchy) proteins, such as myoglobin (see), Tsitokhroma (see), peroxidases (see), catalase (see), etc.
Emergence of early fraction Zh is connected with use of all these sources. item. At introduction to the person 2- 14 S-glycine the tag appears in stercobilin (one of. item) much earlier, than the erythrocytes which apprehended a tag begin to break up. This fraction Zh. the item in turn contains two main components: the component which is formed in a liver and the component which is formed in marrow. The first is connected with metabolism gem in a liver, the second — with an erythrogenesis in marrow. Introduction by an animal 14 With delta and aminolevulinic to - you (an intermediate product in synthesis of porphyrine) quickly lead to emergence of a tag in stercobilinogen that also demonstrates formation of this fraction Zh. the item, in particular its component which is formed in a liver. The early marked fraction quantitatively strongly increases at an inborn porphyria, a thalassemia, pernicious and posthemorrhagic anemias, etc. It can sometimes make even the most part of all allocated to cookies Zh. item. Sharp increase in this fraction under the influence of phenobarbital — the substance strengthening capture and secretion by a liver of organic anions is experimentally shown.
Under some experimental conditions introduction by an animal of marked hemoglobin or hematin is not followed by full removal of a tag with. item. This fact demonstrates existence of other way of degradation of gemsoderzhashchy connections which passes process of education. item. In normal conditions this way, apparently, plays very small role, but can become more active at various patol, states. Introduction by an animal of the allilizopropilatsetamid stimulating formation of porphyrines sharply strengthens this way of a catabolism gem. At the same time in a liver diazonegative connections are formed: mono - and especially the dipirrilmetena which are allocated with bile. It is established also that the denatured hemoglobin which is present at erythrocytes at some diseases of blood breaks up in an organism of animals preferential with formation of dipirrilmeten, but not bilirubin. Believe that in such cases ring structure gem is broken off not in the euzymatic way, and by means of its interfaced oxidation with ascorbic to - that. It is possible that dipirrilmetena can be formed also of already created. the item, however remains still unknown whether the dipirrilmetena allocated with excrements by degradation are formed. the item in intestines or hl. obr. at the expense of the above-stated unusual way of disintegration gem in a liver with their subsequent excretion as a part of bile. Among these connections by the most widespread mesobilifuscin — the brown pigment which is present at excrements is:
Existence of the colourless predecessor of mesobilifuscin — pro-mesobilifuscin is supposed. Also the bilifuscins different from the above-named connections by existence in a side chain of vinyl group instead of ethyl belong to dipirrilmetena. Both that and others as well as calcic salt of bilirubin, are found as a part of the mixed gallstones. The brown-black pigment — kopronigrin which, according to some authors, is polymer of mesobilifuscin is found in excrements. Treats connections of dipyrrol structure and propentdiopent — oxymesobilifuscin which is absent in an organism in normal conditions, but it is found in urine at some forms of jaundice, hemolitic anemia and diseases of a liver. As for porphyrines, they are allocated with urine and excrements in very trace amounts. Though their excretion increases at an increased hemolysis a little, nevertheless it is very small in comparison with excretion of bilirubin.
Bile of the person contains almost only bilirubin and traces of biliverdin. At many animals the pigmental composition of bile differs from pigmental composition of bile of the person. E.g., at herbivorous, reptiles and birds the main thing. the item is biliverdin.
Transformation of bilious pigments in intestines
the bilirubin Arriving with bile, reaching distal department of a small bowel and especially large intestines, is affected by normal intestinal microflora. Under the influence of its enzymes it dekonjyugirutsya and then is consistently recovered with accession of hydrogen atoms in the place one, other double bond that is followed also by processes of dehydrogenation. The amount of the bilirubin still keeping the conjugated form can be involved in initial stages of process of recovery a nek-swarm. The major role in these transformations is played by the enzymes released from anaerobic microorganisms in a caecum. By experiences with fecal flora of in vitro it is established that it is capable to recover completely bilirubin to an end product of its exchange.
In 60 — the 70th 20 century studying of this question became much more fruitful that is connected, to hl. obr., using a method of oxidation by means of iron chloride with the subsequent fractionation and a research of the received products by method mass spectrometry (see). A number of intermediate compounds is allocated. Bilirubin during recovery gradually loses the coloring, turning into colourless chromogens. However at each stage of process by dehydrogenation are formed painted in this or that color Zh. the item (see the scheme 2).
All these transmutation products of bilirubin carry the name of bilirubinoid (if double bonds in situation 2' and 7' remain unsaturated) or urobilinoid (if these bonds are saturated). Besides, all of them can be divided into 4 look depending on quantity of double bonds in the bridges connecting pyrrol groups. Here belong: bilana, free of double bonds in bridges (mezobilirubinogen and further products of recovery of bilirubin); a henbane, containing one double bond (e.g., urobilins, stercobilin); bilidiyena — with two double bonds (e.g., mesobilirubin, belongs to bilidiyena also bilirubin) and bilitriyena — with three double bonds (biliverdin, glaukobilin). An end product of transformations of bilirubin is L - sterkobi-linogen — colourless connection. At contact with air it passes into L-stercobilin — an orange-yellow pigment which among others. the item most of all defines color of excrements (see. Sterkobilin ):
In addition the main way, there is also other way which is considered as bypass. During transformations. the item on this way digidrobilirubinogen gives rise to D-urobilinigen which in turn turns into D-urobilin (see. Urobilin ):
Such shuntovy way to a nek-swarm of degree works also in normal conditions, but hl. obr. joins at change of fermental activity of intestinal microflora, in particular at its suppression by antibiotics of a broad spectrum of activity (tetracycline, erythromycin). At the people receiving these antibiotics in intestinal contents and excrements D-forms Zh sharply prevail. the item, preferential D-urobilin whereas racemic i-urobilin and left-handed urobilinoida normal dominate.
Distinctiveness of a shuntovy way of transformation. the item in intestines is preservation of vinyl group (V) at the first pyrrol ring and, thus, formation of monovinyl derivatives. Assume that hydrogenation of a double bond in this situation is catalyzed by highly specific enzyme which is lost or is very poorly formed at suppression of microflora by antibiotics. In these conditions hydrogenation of metinovy bridges, than vinyl group at the first pyrrol ring proceeds easier. At the same time ability of microorganisms to produce the additional energy necessary for transformation of D-urobilinigen into its L-derivatives decreases. Molecules of urobilinoid have no line structure, and are curtailed thanks to education in a molecule of hydrogen bindings (see a constitutional formula of L-stercobilin). The rupture of hydrogen bindings, expansion of a molecule and then again its coagulation in other situation is necessary for change of their configuration. At the same time further hydrogenation of connection shall proceed. It is natural that in the conditions of change of activity of microflora such processes connected with expense of additional energy are weakened. Therefore turning on of the monovinyl shunt results in sharp dominance in total quantity. item D-urobilinoidov.
It is noted also that at suppression of activity of intestinal microflora antibiotics of transformation of bilirubin can be late or stop at any intermediate stage. In this case not changed bilirubin which is present at excrements can be oxidized on air in biliverdin which gives them a green shade.
Various transmutation products of bilirubin in very trace amounts are soaked up in blood and reekskretirutsya by a liver as a part of bile. Their traces can appear in the general blood-groove and be allocated with urine. All these processes amplify at patol, the states which are followed by increase in release of bilirubin with bile. Urobilinigen even normal in noticeable quantities passes into blood of a portal vein and, being oxidized in a liver to bilirubin, is again excreted, and partly emitted with bile in neopussycats Lynn a look.
It is established that a nek-swarm the amount of bilirubin after a dekonjyugirovaniye in intestines passes into blood of a portal vein, it is conjugated in a liver and excreted with bile.
The fact of absorption of a significant amount of free bilirubin and, apparently, urobilinigen and their resekretion after the corresponding turning into composition of bile speaks about participation. the item in pechenochnokishechny circulation. Though rather small part of all bilirubin which came to intestines, unlike circulation is involved in this process bile acids (see), nevertheless existence of circulation. the item raises a question of whether they have any value in secretory activity of a liver. In hepatic bile bilirubin is in structure of its lipidic complex representing endogenous lipidic micelles. Such micelles are capable to include various connections possessing polar and unpolar groups. It is possible that the bilirubin which is especially conjugated with the acid disaccharides giving it sharply expressed polar properties, joining in this lipidic complex, stabilizes its micelle structure and by that promotes transport of various substances as a part of bile.
Disturbances of the mechanism of excretion of bilious pigments
At some patol, states are observed disturbances of education, transport and allocation. the item (see. Jaundice ). The specific mention is deserved by cases when the scholia in biliary system (in connection with obstruction of bilious ways or at severe forms of cirrhosis) is followed by oxidation of a part of bilirubin in biliverdin which also passes into blood and gives to icteric coloring of scleras, skin and mucous membranes a greenish shade.
Also the wedge, data on inherited disorders of separate links in the mechanism of transformation and excretion are of great interest experimental. item. So, at the mutant rats described by the Hun (S. of Gunn, 1938), the liver is deprived of ability to conjugate bilirubin. It depends on a lack of education or total absence of a liver of specific enzymes. The colony of such animals was tracked within 19 years, and belonging of the specified defect to number of inherited disorders with obviousness was shown. At such rats bile is colourless and almost does not contain bilirubin at all. In blood serum the content of not conjugated bilirubin to the maximum level (15 — 20 mg of %) increases. Jaundice develops, edges, as a rule, is followed by functional and structural disturbances of c. N of page. At these animals the pigment with urine is not allocated, but it is allocated with a mucous membrane of intestines in a gleam of guts. Besides, a part of bilirubin turns into diazonegative connections, apparently mono - and dipirrola which are allocated with bile and urine. If such animal enter glucuronides of bilirubin, they are excreted as a part of bile. Administration of not conjugated bilirubin does not cause increase in allocation of a pigment with bile. Thus, disturbances of exchange. items at these animals are connected with frustration of only one link — a konjyugirovaniye of bilirubin in a liver.
Other hereditary defect is described at mutant sheep at whom at preservation of ability to conjugate bilirubin process of its allocation of cells of a liver in bile is broken. Possibly, it depends on a lack of a specific carrier of the conjugated bilirubin through a cellular membrane. Excretion of a pigment as a part of bile at these animals is sharply lowered. In blood not the free, and conjugated (direct) bilirubin collects. At the same time in a liver presence of an unusual pigment of the melaninovy nature which, apparently, is formed as a result of the lowered ability of a liver to allocate metabolites of some amino acids and close connections to them is found. At the same time secretion bilious to - t at these animals is not broken, and, therefore, they have no intra hepatic cholestasia, at Krom the general disorders of secretion of a liver affecting allocation of various components of bile are observed. In this case only one end body in the mechanism of excretion is broken. item.
At the person the similar disturbances (a syndrome the Cudgel — Johnson) which are characterized hron, not hemolitic jaundice with high content in blood of the conjugated bilirubin and presence of a melaninovy pigment at a liver are described (see. Hepatoses ). This disease has family character and also is connected with frustration of the mechanism of secretion of glucuronides of bilirubin and some other organic anions, except for bilious to - t, from cells of a liver in bile. Detection and detailed studying of inherited disorders in an experiment makes a valuable contribution to understanding of hepatic transport. the item is also of great importance in interpretation of genesis of the corresponding syndromes observed at the person in clinic.
Fiziol, jaundice of newborns is connected, apparently, with an insufficient maturity of fermental system of a liver responsible for transformation of bilirubin. The hereditary hyperbilirubinemia of the person is also followed by disturbance of process of a konjyugirovaniye of bilirubin, increase in content in blood serum of an indirect bilirubin (see. Hyperbilirubinemia ).
Determination of content of some. the item in blood serum, urine and Calais is used at a wedge, inspections of patients as additional diagnostic test at a number of diseases. So, increase in content in urine of urobilinigen at norm of 0 — 4 mg a day (see. Urobilinuria ) it is observed at hepatitises in their initial stage (see. Hepatitis , viral hepatitis ), at necroses of a liver (see), at toxic damage of a liver (see. Toxic dystrophy of a liver ), portal cirrhosis, obturation of the infected bilious ways, and also at congestive heart failure, heavy acute infections, a heart attack of a lung, heavy hypodermic hemorrhages. Normal in Calais the person 40 — 280 mg of stercobilinogen a day are defined (at children of figure slightly lower), however at hemolitic anemia at normal function of a liver removal of stercobilinogen with a stake increases, and at obturation of bilious ways, heavy hepatopathies, a cachexia, some anemias and at reception of antibiotics of a broad spectrum of activity — decreases.
Adjournment of bilious pigments in bodies
Adjournment. the item happens in bodies, fabrics and cells at different types jaundices (see), especially at obturatsionny jaundice, at hemolitic disease of newborns (see), bilirubinovy heart attack (see), in case of a prokrashivaniye bile of nekrotizirovanny fabric, and also after hemorrhages.
K Zh. items, distinguishable in cells and fabrics in a light microscope and revealed gistokhy, methods, carry bilirubin, biliverdin and gematoidin. The last pigment on a structure is identical or close to bilirubin. Chemical and physical. properties Zh. items allow to distinguish quite easily them histochemical [A. G. E. Pearse, 1962; Lilly (R. D. Lillie), 1969]. They do not possess primary luminescence, are insoluble in the most part of fatty solvents and do not become colourless under the influence of oxidizers. Positive reaction of Gmelin, intensive recovery of ferricyanide and blackening after processing by ammoniac silver are characteristic of bilirubin and a gematoidin at 250 ° during 5 — 16 hours Gistokhim, Gmelin's reaction (see. Gmelina test ) it is carried out by introduction under cover glass konts. nitric to - you with the subsequent bystry research of a cut under a microscope. In the sites containing bilirubin and crystals of a gematoidin transition of flowers from red to green, purple and blue is observed. It is caused by oxidation of pigments in greenish bilirubin (bilatriyen) and in reddish-violet bilipurpurins. At the final stage of reaction blue connections are oxidized in yellow holetelina. In a row gistokhy, methods use oxidizers for the purpose of transformation of yellowish-brown bilirubin into green biliverdin. To such methods treat the J. Stein method using iodine (solution of Lugol and tincture of iodine) as an oxidizer, G. Glenner's method with oxidation by potassium bichromate in acid medium (pH 2,2), oxidation on Kutlika (I. E. Kutlik, 1957) ferri-compounds (FeCl3, etc.). To check whether really the pigment which is present at fabric is bilirubin, during the performance of the specified reactions it is necessary to be convinced that in the control cuts which were not affected by an oxidizer, the pigment has brown color and after oxidation this color turns into green. Use of ferroprussiate allows to bring process of oxidation of bilirubin further away, than at the reactions stated above, namely to a stage of bilipurpurins.
Adjournment. the item (bilirubin and biliverdin) at patol, states it is possible to observe in tissues of a liver, kidneys, a brain, intestines and other bodies. Noticeable accumulation. the item in a liver happens at extrahepatic and intra hepatic cholestasia (see). Slush stocks. items in the form of so-called bilious blood clots accumulate in a gleam of small bilious channels and expanded bilious capillaries. Transformation of a part of bilirubin into biliverdin gives to bilious blood clots a greenish shade. Granules. items contain at a cholestasia also in cytoplasm of hepatic cells and star-shaped endotheliocytes (Kupfer's cells). At a submicroscopy in the damaged hepatic cells find. the item in the form of big amorphous accumulations of spherical shape, partially or completely surrounded with a single-layer membrane, or in the form of the acerate electron-dense little bodies surrounded with a membrane of the broken-up mitochondrions; in intercellular spaces and bilious capillaries. items have an appearance of the electronic and dense and acerate educations which are not surrounded with membranes. The strengthened allocation. the item kidneys at obturatsionny jaundice is followed by their accumulation in hyaline and granular cylinders of renal tubules (a so-called icteric nephrosis). At a hemolitic disease of newborns there is a kernicterus with a prokrashivaniye. item of kernels of big hemispheres and trunk of a brain. At the same time there is an irreversible damage of ganglionic cells of a brain. Nekrotizirovanny fabrics easily adsorb bile together with. item. Explain these chartreuse coloring of peyerovy plaques and solitary follicles at a typhoid and an imbibition. the item of the centers of a necrosis of a parenchyma of a liver at biliary cirrhosis. Yellow color of a liver at an acute massive necrosis or the acute toxic dystrophy arising as a complication of an infectious disease is also caused by a prokrashivaniye of nekrotizirovanny fabric Zh. item. According to I. V. Davydovsky. the item together with bilious to-tami, getting into fabrics, can have necrotizing effect on them.
Gematoidin is found in the field of extensive old hemorrhages and hemorrhagic heart attacks. The pigment has an appearance of golden-yellow grains or crystals in the form of asterisks, needles, rhombic plates. It is formed intracellularly in the macrophages who absorbed decomposition products of hemoglobin. After destruction of macrophages the pigment is located vnekletochno in the center of hematomas.
Bibliography: Davydovsky I. V. General pathology of the person, M., 1969; Lille R. Patogistologicheskaya of the technician and a practical histochemistry, the lane with English, M., 1969; Nesterinm. F Narodetskaya R. V. and Shlygin G. K. Department liver as a part of bile of lipoprotein complex connection, Fiziol, zhurn. USSR t. 51, To 12, page 1487, 1965; Pearce E. A histochemistry, the lane with English, m of 1962; Sh l y and G. K N. Modern ideas of direct participation of digestive tract in a metabolism, Vestn. USSR Academy of Medical Sciences No. 12 of page 27, 1968; To 1 a t s k i n G.’ Bile pigment metabolism, Ann. Rev. Med v. 12, p. 211, 1961, bibliogr.
G. K. Shlygin; V. B. Zolotarevsky (gist.).