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Chinieva Marina Ilinichna, Assistant of Department of Histology and Pathological Anatomy
of Tashkent Pediatric Medical Institute Rasulova Khurshidakhon Abduboriyevna, Head of Department of Coordination of Research Activity of Tashkent Pediatric Medical Institute Zakirova Nargiza Bakhodirovna, DSc, dosent of Department of Histology and Pathological Anatomy of Tashkent Pediatric Medical Institute E-mail: nargiz72@mail.ru Rakhmanov Alisher Khudayberdiyevich, Head of Pharmacology and Toxicology Department of Tashkent Medical Academy Kendjaeva Khilola Khudayberganovna, Assistant of Department of Histology and Medical Biology of Tashkent State Dental Institute, Uzbekistan E-mai: evovision@bk.ru
MORPHOLOGICAL CHANGES IN STRUCTURES OF KIDNEY TUBULAR AND VASCULAR SYSTEMS UNDER PROTEIN HOMEOSTASIS DISTURBANCE IN RATS
Abstract: The regulation of protein homeostasis is provided by structural-functional systems, and can be accompanied by proteinuria. Therefore, in order to study the structural bases of integration of functional kidney systems in the regulation of protein homeostasis, was reproduced a model for the disturbance of protein homeostasis in blood in rats. The morphological study of the kidney established that, under different physiological conditions, there are regular changes in the cells ofthe juxtaglomerular apparatus and capillaries of the glomeruli of superficial and juxtamedullary nephrons, which are aimed at increasing the functional reserve of the kidneys in regulating protein homeostasis.
Keywords: protein loads, kidneys, glomerular filtration rate, arterioles, juxtamedullary nephrons.
Introduction Due to its homeostatic role in the body, the kidneys
The life of the organism is a wide spectrum of ge- are extremely sensitive to changes in diet. In addition, the
netically programmed continuous reconstructions in kidneys perform not only excretory, but a number of im-
response to the action of various factors of the external portant functions, in particular metabolic and homeostat-
and internal media, changes in the parameters of ho- ic. Despite the fact that the kidneys are very sensitive even
meostasis arising from the dynamism of constantly go- to the slightest fluctuations in the content ofvarious ingre-
ing metabolic processes. Formed as a result of evolution, dients in the diet, it may take a different amount of time for
adaptive reactions are realized in ontogeny as genetically full development of renal response to changes in the intake
programmed, and for all their varieties are subdivided of a particular substance. To decipher the mechanisms of
into relatively fast (fractions of a second, seconds) and homeostatic functions of the kidney, the integration of
slow (days, months, years) [5]. functional systems that ensure its functioning, a model of
Section 5. Medicine
protein load was reproduced in different age periods. At the same time, the structural mechanisms of interaction of various functional kidney systems with different physiological states remain insufficiently elucidated [2].
The purpose of this work was to identify the structural basis for the integration of certain functional kidney systems in the regulation of protein homeostasis.
Materials and Methods
The experiments were performed on forty-five sexually mature non-native white rats, weighing 140-160 g. The first group of rats (n = 15) had rotein load on the kidneys by parenteral single and repeated administration of albumin. The second group of rats (n = 15) underwent protein starvation, without restriction of access to water. The third group of rats (n = 15) served as a control.
In all series of experiments, the right kidney was cut through the middle from the convex surface to the gate area. Then a plate 1.5 mm thick was cut out parallel to the plane of the cut and the cortex was separated from the cerebral. Subsequently, the cortical part ofthe kidney was cut into three equal parts: internal, intermediate and superficial. The kidney tissue corresponding to the superficial and juxtamedular nephrons was fixed in 2.5% buffer solution with glutaraldehyde acid. The process of making the sections of the tissue under investigation was performed on ultramicrotome using the general method used in electron microscopy. Sections were mounted on a slide, dried at room temperature and stained with methylene blue and fuchsine. Microscopic images were performed on a light microscope equipped with a digital camera.
The tissue of the kidneys at the 1st, 3rd and 7th day of the experiments was studied by morphometric and electron-microscopic methods.
Results and Discussion
The results showed that at 1st day of protein load there were dilation of the afferent and narrowing of the efferent arterioles, an increase in the percentage of glomeruli with a greater degree of opening of the blood capillaries and activation of cells of the juxtaglomerular apparatus [1].
The structure of cells of the proximal tubules was not changed. It was characterized by a light homogeneous cytoplasm with basally located nuclei. Mesangial matrix was present in a small amount, in which only single me-sangiocytes were detected.
After 3 days with normalization of structure of the juxtaglomerular apparatus, the degree of opening of the
blood capillaries ofboth surface and juxtamadullar nephrons exceeded the parameters of control animals.
The cells of the dense spot were enlightened; the extent of the basal and lateral parts of their outer membrane was enlarged. Juxtavascular cells were hypertrophic and contain secretory granules. Mesangiocytes became larger in protein load, they acquired an irregular shape.
When fasting after 3 days the degree of opening of the blood capillaries increased, however, activation of the juxtaglomerular apparatus was not observed [4].
After 7 days, the degree of opening of the blood capillaries remains high only in juxtamidullary nephrons [3].
The regular morphological changes in various parts of the nephron were detected light-optically. There was increase in the size of the glomeruli with the expansion of the urinary space of the Bozeman capsule, the expansion of the mesangial matrix with a moderate increase in the number of mesangiocytes, adhesion of the capillary loops to the capsule walls, and compression of the capillary loops. In addition, focal sclerosis of the capsule and sclerosis of the capillary loops were detected in some glomeruli. Significant changes were found in the proximal tubules. Among them, increase in the content of secretory granules in the cytoplasm of cells, the swelling of the apical part of the cytoplasmic membrane of tubular cells in the lumen, as well as the apical and intermediate position of nuclei in a significant number of cells.
Thus, under different physiological conditions, regular changes occur in the cells of the juxtaglomerular apparatus and capillaries of the glomeruli, the tubules of the superficial and juxtamedullary nephrons, which are aimed at increasing the functional reserve of the kidneys.
In control animals juxtaglomerular cells of the afferent arterioles are the main renin-producing component of the juxtaglomerular apparatus of the kidneys [9]. They are polygonal in shape, contain numerous organelles: the profiles of the rough reticulum, which are evenly distributed throughout the cytoplasm, closely interact with rounded, moderate-sized mitochondria; The Golgi complex is localized near the nucleus. Secretory granules in a moderate amount, rounded, high electron density, evenly distributed throughout the cytoplasm. These data indicate their moderate functional activity [7].
In the wall of the efferent arterioles, the juxtamendul-lar cells are smaller and contain less secretory granules than in the wall of the afferent arterioles. Cells of a dense
spot of cylindrical shape, basal folds single, low, do not contact mitochondria, diffusely distributed along the cytoplasm. In the areas of contact of the plasmolemma of cells, the basal membrane is thin, discontinuous [8].
Juxtavascular cells located between the afferent and efferent arterioles, irregularly elongated, poor in organelles, rich in ribosomes and polysomes. The mesangial cells are located between the glomerular capillaries, almost identical in ultrastructure to the juxtavascular [2, 6].
Conclusions
The data obtained indicate that a single protein load is accompanied by activation of the juxtaglomerular complex and change in the functioning of nephrons.
Morphological data characterize the relatively early stages of development of experimental chronic renal dysfunction, since along with obvious morphological signs of changes in glomerular hemodynamics and dystrophic changes in the tubules, only initial evidence of nephrosclerosis formation was found.
The obtained data opens new prospects for studying the role of kidneys in protein metabolism in developing renal failure, including tubular reabsorption of not only endogenous, but also exogenous proteins, and draw attention to the need to study the violations of the most important non-excretory functions of the kidneys and their consequences in analyzing the progression of nephropathies.
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