Morphological state of the liver and thyroid gland of male and female rats with experimental obesity under iodine action Текст научной статьи по специальности «Фундаментальная медицина»

BIOLOGICAL SCIENCES

MORPHOLOGICAL STATE OF THE LIVER AND THYROID GLAND OF MALE AND FEMALE RATS WITH EXPERIMENTAL OBESITY UNDER IODINE ACTION

Kopchak N.H.

Pokotylo O.S.

Department of Food Biotechnology and Chemistry, Ternopil Ivan Puluj National Technical University, Ternopil, Ukraine

ABSTRACT

The article provides the reader with some information on impact obesity on lipid metabolism. Much attention is given to influence iodine on morphological state of the liver and thyroid gland. The purpose of our study is to determine the histological state of liver and thyroid gland of white rats, males and females, with experimental obesity under the action of biologically active iodine.

The research was conducted on 36 mature males and females of white rats of the Vistar line. Animals of each sex were divided into 3 groups and 6 animals in each. The 1st is an intact group, which received the basic vivarium diet; the 2nd and 3rd groups are with experimental alimentary obesity (EAO). Daily during 45 days, animals of the 3rd group received intragastrically intravenous iodine in the form of "Jodis-concentrate" in a dose of 0.1 ml (0.4 micrograms of iodine) per kg of body weight per day.

For histological researches, pieces of liver and thyroid glands of animals were taken. Microscopic studies of the liver and thyroid gland of mature males and females of the intact group have shown that it has no specific features. Under the conditions of experimental obesity in the liver and the thyroid gland of animals there are destructive and dystrophic changes of its components. Microscopic studies of the liver and thyroid gland of animals, in the context of correction of experimental obesity with iodine, determined the improvement of the structural organization of the organ in comparison with the group of experimental animals, where no corrections were made.

Keywords: liver histology, thyroid gland histology, white rats, obesity, sex, Jodis-concentrate

Introduction

At the moment of obesity, all types of metabolism are violated and a number of organs are affected, and especially the liver involved in all metabolic processes [7]. It has a major part in lipid metabolism, influencing biosynthesis and lipid transformation, maintaining the optimal level of some lipid fractions in the blood [8]. Endocrine disorders can be both a cause and a consequence of overweight [6].

Obesity and hypothyroidism are two clinical states that are closely connected with each other [4]. The thyroid gland and the liver have interdependent metabolic effects, because the thyroid hormones regulate the intensity of metabolism in hepatocytes and undergo transformations with the participation of liver deiodinase [2,10,18]. At the pathological states of one of these organs, the state of another is exacerbated (depressed) in the form of dysfunction or morphological changes [5,17].

Hypothyroidism is a disease that leads to weight increase [6]. In hypothyroidism, there are changes in the hepatic tissue, namely, fatty liver infiltration [11]. In addition, thyroid dysfunction, especially with iodine deficiency, also leads to a change in its structure, and in accordance with a decrease in the synthesis and secretion of T3 and T4 [12,15]. In the scientific literature, mostly, there are data on biochemical changes in the blood, liver and thyroid gland in terms of modeling obesity in laboratory animals [1,13] and, to a less extent, morphological changes are presented.

Therefore, the aim of our study is to determine the histological state of liver and thyroid gland of white rats, males and females, with experimental obesity under the action of biologically active iodine.

Materials and methods

The research was conducted on 36 mature males and females of white rats of the Vistar line. They were in the appropriate sanitary-hygienic conditions of the vivarium of SHEE I. Horbachevsky Ternopil State Medical University of the Ministry of Health of Ukraine and got a standard balanced diet.

Animals of each sex were divided into 3 groups and 6 animals in each. The 1st is an intact group, which received the basic vivarium diet; the 2nd and 3rd groups are with experimental alimentary obesity (EAO). EAO were formed through an inductor of a food traction - a sodium glutamic acid salt in the ratio of 0.6: 100.0 and a high calorie diet that included standard food (47%), sweet concentrated milk (44%), corn oil (8%) and vegetable starch (1%) [3]. Daily during 45 days, animals of the 3rd group received intragastrically intravenous iodine in the form of "Jodis-concentrate" in a dose of 0.1 ml (0.4 micrograms of iodine) per kg of body weight per day.

During 45 days of an experiment, it was control of reproduction of alimentary obesity by weighing animals, measuring nasal-anal length and calculating the body mass index (BMI) - dividing the body weight in grams by the length in square centimeters. At the end of the experiment, the animals were killed by decapitation under thiopental anesthesia. During the experiment, the requirements of the European Convention for the Protection of Vertebrate Animals used for Experimental and Other Scientific Purposes (Strasbourg, 1986), the Law of Ukraine On the Protection of Animals from Cruelty and the EU directive 2010/10/63 on the protection of animals used for scientific purposes were kept.

For histological researches, pieces of liver and thyroid glands of animals were taken, fixed in 10% neutral formalin [16]. Further processing of the material with subsequent pouring in paraffin blocks was carried out according to generally accepted techniques. Received on the sledge microtome sections of 5-6 microns were colored with hematoxylin-eosin [9,14]. Histological preparations were studied using the optical microscope SEO SCAN and photo-documented with a Vision CCD Camera with an image display system for histological preparations.

Research results discussion

Microscopic studies of liver of mature males and females of the intact group have shown that it has no specific features. Parenchyma of the organ has a lobulation structure. Lobulations are tight, between them there is a stromal loose areolar connective tissue that is poorly developed and does not have clear shapes. It is more developed in the areas of triads. Hepatocytes are the cells of the lobulation arranged in an ordered manner in the form of radially oriented cords. They are bands from the periphery of the lobulation to the central vein. Blood sinusoidal capillaries are between the cords (Fig. 1, 2).

Fig. 1 Microscopic organization of rat's liver - male of the intact group. Central vein (1), cord location of hepatocytes (2) in the lobules, hemocapillary (3). Coloring with hematoxylin eosin. x 200

At the corners of the lobulation there are triads intercellular artery, vein and bile duct (Fig. 2)._

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Fig. 2 Microscopic organization of rat's liver - female of the intact group. Triads (1) Central vein (1), cord location of hepatocytes (2) in the lobulation, hemocapillary (3). Coloring with hematoxylin eosin. x 200.

Hepatocytes have polygonal form, in cells there are one or two nuclei, in their karyoplasm there are basophilic materials of chromatin and nucleoli. The cytoplasm has an oxyphilic color and includes basophilic material. The hemocapillary wall is formed with oblong-shaped endothelial cells, and there are also Kup-ffer cells, macrophages of sinusoids.

Microscopic studies of liver of animals with experimental obesity revealed significant changes in the structural components of the body, compared with the intact group of rats. Both, in the mature males and females, the reorganization of the liver was similar. Sig-

nificant changes in blood vessels, their blood-filled vessels, central and underlobular veins enlargement were observed, their walls were thin and with unclear shapes.

Histologically, animals in the experimental group had changes in the cord structure of lobules, especially in their periphery. There is a disorderly arrangement of hepatocytes, an increase in the area of their cytoplasm. Hypertrophy of cells, change in their forms were accompanied by signs of dystrophy, decreased oxyfilia and vacuolation of the cytoplasm. Some of the hepato-cytes looked like as devastated structures with picnotic, eccentrically located nuclei (Fig. 3).

Fig. 3 Histological changes of rat's liver - male under the conditions of experimental obesity. Wide, blood-filled central vein (1), destructively changed hepatocytes in the lobulation (2). Coloring with hematoxylin and eosin. X

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Destructive changes in parenchyma of lobulations have also been developed as fatty degeneration of cells. A fatty degeneration with small fat droplets and a fatty

degeneration with large fat droplets of the cytoplasm were noted, but the last one was clearer in the lobulation of the dense duct of females (Fig. 4).

Fig. 4 Histological changes of rat's liver - female under the conditions of experimental obesity. Triads (1), leukocyte infiltration (2), damaged hepatocytes (3). Coloring with hematoxylin and eosin. X 200

Clear space of sinusoid hemocapillaries is uneven, narrow and expanded sections are available. In the composition of the triad there are wide, blood-filled elements, veins. The arteries have smaller diameters and thickened walls. There is moderate leukocyte infiltration of the connective tissue in the area of the triads.

Thus, under the conditions of experimental obesity in the liver of animals there are destructive and dystrophic changes of its components, which are developed into organ steatosis, vascular disorders, disturbances in the structure of the lobulation, hypertrophy and

fatty degeneration of hepatocytes shown mostly in females.

Microscopic studies of liver of animals, in the context of correction of experimental obesity with "Jodis-concentrate", determined the improvement of the structural organization of the organ in comparison with the group of experimental animals, where no corrections were made. Histologically, the vascular bed destruction is less noted, central and underlobular veins are enlarged, but not so much as in liver of animals without the use of "Jodis-concentrate" (Fig. 5).

Fig. 5 Microscopic state of rat's liver - male under conditions of correction of experimental obesity with "Jodis-concentrate". Moderately enlarged space of the central vein (1), unchanged hepatocytes (2), moderate fatty degeneration of hepatocytes (3). Coloring with hematoxylin and eosin. x 200

The structural state of the lobulation and their cord structure were also improved as compared to the untreated animal group. There are no many parts of destructively changed hepatocytes. Most cells had cytoplasm with an ordinary oxyphilic color, and their round nuclei were clearly shaped. However, the presence of hepatocytes with picoty basophilic nuclei and signs of

vacuoles and fatty degeneration were noted. Such changes are mainly found in the peripheral parts of the lobulation and more showed in the liver of female rats.

In the portal tracts, the vessels also look moderately changed, minor perivascular edema and leukocyte infiltration of stromal connective tissue are investigated too (Fig. 6).

Fig. 6 Microscopic state of rat's liver - female under conditions of correction of experimental obesity with "Jodis-concentrate". Space of the central vein (1), unchanged hepatocytes (2), moderate fatty degeneration of hepatocytes (3). Coloring with hematoxylin and eosin. x 200

Thus, it is microscopically established that under the conditions of correction of experimental obesity with iodine, the structure of the liver is improved, as compared with the group of untreated animals. Destructive and dystrophic changes in its components, vascular disorders are insignificant. Fewer changes in the lobu-lation of organs, fatty dystrophy of hepatocytes and their hypertrophy are only available in peripheral areas and mostly in females.

Microscopic studies of the thyroid gland of mature males and females of the intact group have shown that it has no specific features. Histologically, the endocrine organ of white rats, males and females, consists of parenchyma and stroma. The parenchyma is separated by thin layers of loose areolar connective tissue into lobu-lation. The lobulations include follicles that have

mostly rounded shape and different sizes of their areas - small, medium, large.

The follicle wall is built with a single layer of endocrine cells, tyrocytes. In intact animals, tyrocytes are predominantly square-shaped located on the basement membrane, which corresponds to their normal function. Nuclei of tyrocytes are characterized by rounded shapes, clear contours, their karyoplasms are colored moderately with basophilic color. Cell cytoplasm is homogeneous, basophilic in the basal part and with acidophilic tint in the apical region. Space of follicles is filled with moderately oxyfilic substance - a colloid, which is a product of thyrocyte secretion. In the layers of the connective tissue and near the wall of the follicles, there are blood capillaries with a thin wall and non-wide spaces (Fig. 7), (Fig. 8).

Fig. 7 Structural organization of lobulations of the thyroid gland of a rat - male of the intact group. Follicle (1), colloid (2), layers of loose connective tissue (3). Coloring with hematoxylinum and eosin. x 200

Fig. 8 Microscopic structure offollicles in the lobulations of the thyroid gland of a rat - female of the intact group. Thyrocytes of the follicle (1), colloid (2), blood capillary (3). Coloring with hematoxylinum and eosin. X

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Microscopic studies of the structural state of the thyroid gland of animals in the conditions of experimental obesity have established that in lobulations, most follicles keep their inherent shapes, but there are deformed with a rough wall of the follicle. Their walls

are covered with flat thyrocytes, which have small basophilic nuclei and little cytoplasm. Follicle spaces are filled with non-absorbing oxyphil colloid. Among the large ones, there are some middle and small areas of follicles (Fig. 9).

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Fig. 9 Structural organization of rat's thyroid gland lobulations in the conditions of experimental obesity. Significant area of the follicle (1), colloid (2), enlarged blood-filled vessel (3). Coloring with hematoxylinum

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Such structures are located mainly on the periph- Microscopic studies of the structural state of the

ery of lobulations. Tyrocytes in their walls have a rec- thyroid gland of a rat - female in conditions of experi-

tangular or low-prism form. The coloid in the follicles mental obesity, have shown that hypertrophied follicles

is stained more intensively than the preparations of the with a significantly thin wall are in lobulations. Thyro-

thyroid gland of intact animals, it looks denser and cytes become flat, small basophilic their nuclei look

there are rarely observed vacuoles of resorption and pycnotic. They are surrounded by a small area of the

space of colloid near the apical plazmol tyrocytes. cytoplasm. Follicle spaces are filled with non-absorb-

Edema of stromal loose areolar connective tissue is ob- ing oxyphil colloid. There is also significant stromal

served, vessels are enlarged and blood-filled, especially and perivascular swelling of the connective tissue and

veins and venules. leukocyte infiltration (Fig. 10).

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Fig. 10 Microscopic structure offollicles in the lobulations of the thyroid gland of a rat - female in conditions of experimental obesity. Hypertrophied follicle (1), layers of loose connective tissue with enlarged blood-filled

vessels (2) x 100.

Investigated histological changes of the structural components of the thyroid gland correspond to the hypofunction of the organ.

Microscopic studies of the thyroid gland of animals, in the conditions of correction of experimental obesity with "Jodis-concentrate", have shown the improvement of the organ structure comparing to a group of experimental animals, where no correction was performed. Most follicles are medium or small; there are

only some of large sizes. Their walls are formed by ty-rocytes of predominantly square shape, which contact with the basal membrane. A rounded shape and clear contours of carriel are specified for nuclei of endocrino-cytes, and their karyoplasms are colored basophilic moderately. Cell cytoplasm is homogeneous, baso-philic moderately in the basal part and with acidophilic features in the apical area. However, some of the cells have optically light cytoplasm (Fig.11).

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Fig. 11 Microscopic state of the thyroid gland of a rat - male in conditions of correction of experimental obesity with "Jodis-concentrate". Medium (1) and small (2) follicles, colloid (3), stroma with hemocapillary (4).

Coloring with hematoxylin and eosin. x 200

Edema of the stromal loose areolar connective tissue is negligible, vessels are moderately enlarged and blood-filled.

Microscopic studies of the structural state of the thyroid gland of a rat - female in experimental obesity under the conditions of the use of iodine preparation, which contains small and medium follicles in the lobu-

lations, but unlike male rats, hypertrophied with significant colloid structures are noted. The condition of most thyrocytes in the wall of the follicles is improved, they have a square and a low prism shape, well-structured nuclei. The cytoplasm of most endocrinocytes is homogeneous, moderately basophilic in the basal part and with acidophilic feature in the apical region. Some ty-rocytes have an optically light cytoplasm (Fig. 12).

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Fig. 12 Microscopic state of the thyroid gland of a rat - female in conditions of correction of experimental obesity with "Jodis-concentrate". Large (1), medium (2) and small (3) follicles, colloid (3), stroma with hemocapillary (4). Coloring with hematoxylin and eosin. x 100

Thus, histological studies of the thyroid gland of white rats with experimental obesity under the conditions of iodine use, have found that in males and females the structure of thyrocytes is significantly normalized in most follicles, microscopic states of stroma and vessels are slightly changed.

Conclusions

Microscopic studies of the liver and thyroid gland of mature males and females of the intact group have shown that it has no specific features.

Under the conditions of experimental obesity in the mature males and females, the reorganization of the liver was similar, there are destructive and dystrophic changes of its components, which are developed into organ steatosis, vascular disorders, disturbances in the structure of the lobulation, hypertrophy and fatty degeneration of hepatocytes shown mostly in females. Microscopic studies of the structural state of the thyroid gland of second groupe both sex, have shown that hy-pertrophied follicles with a significantly thin wall are in lobulations, thyrocytes become flat, follicle spaces are filled with non-absorbing oxyphil colloid.

Histological studies of the thyroid gland of white males and females rats with experimental obesity under the conditions of "Jodis-concentrate" use, have found that the structure of thyrocytes is significantly normalized in most follicles, microscopic states of stroma and vessels are slightly changed and the structure of the liver is improved, as compared with the group of untreated animals.

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