|
MODERN IN VIVO METHODS OF STUDY OF MEMBRANE HYDROLYSIS
ANDNUTRIENTS ABSORPTION IN SMALL INTESTINE OF SMALL LABORATORY
ANIMALS
B.Z. Zaripov (Academician), V.A. Karimov (candidate of biological sciences),B.A. Niyazmetov
(lecturer), S.L. Rakhmatkhanova (master student), H.A. Rakhmanova (master student), H.Y. Kayumov
(master student), M. Kholniyoziva (master student)
National University of Uzbekistan, Biology faculty, Physiology and Biophysics department,
academician. Fergana State University
Various experimental methods and approaches are used at study of digestion and
absorptionprocessesin small intestine. Thus, considerable progress at study of membrane hydrolysis
mechanisms and nutrients transport insmall intestine was achieved in experiments
in vitro
using
various experimental models (from small intestine segments to isolated enterocytes and membrane
vesicles). However, the main laws of the functioning of various systems in the integral organism and
the real scale of the processes occurring in it can be revealed only at usage of integrative experimental
models, where suchnatural conditionsare provided that close to physiological ones.
To date, a methodof studyhydrolysis and absorption of various nutrients in the isolated section of
small intestine has been widely used at its perfusion
in vivo
of anesthetized animals by solutions of the
corresponding substrates. It is believed, that data obtained in these experimental conditions, due to the
preservation of the structure of the small intestine, blood supply and innervation, most fully
characterize the studied processes.
At the same time, in chronic experiments on rats using the methodcreated by A.M. Ugolev and
B.Z. Zaripov, it was shown that anesthesia and surgical trauma significantly reduce the hydrolysis rate
and nutrients absorption insmall intestine and significantly affect the kinetics of these processes [1].
Analysis of the results of chronic experiments with the use of mathematical modeling allowed us
to determine the true values of the kinetic constants of membrane hydrolysis and transport of various
food substances, taking into account the diffusion permeability of the pre-epithelial layer of small
intestine, to evaluate the role of factors ensuring a high degree of conjugation of the oligomer
hydrolysis processes and the absorption of monomers in the small intestine, the contribution of active
transport and facilitated diffusion in the transfer of glucose through the apical membrane en
enterocytesclose to physiological conditions.Essential shortcomings of this technique are: progressive
atrophy of the isolated intestine area due to the absence of exogenous functional load in it and the
impossibility of a full study of the hydrolysis of food biopolymers due to the stopping of the delivery
of gastric and pancreatic juices and bile to the isolated area of small intestine.
A method, in which the functioning portion ofsmall intestine that receives a natural load is
perfused, is free from these shortcomings [2]. The formation of the ―living‖ fistula and the main part of
intestine in the course of the surgical operation of the Y- shaped test site during the experiment, but
retains the passage of the chyme over it at the rest of the time without loss of intestinal contents. In this
case, hydrolysis rate and absorption of substrates in the intestinal regionof the intestine is much higher
than in the experiments with its complete isolation.Unfortunately, this method also has its
drawbacks:complexity of the surgical operation, the need to use an unabsorbable label to assess water
absorption, the uncertainty of the length of intestine region in which the cleavageorabsorption of the
test substrate actually occurs, due to a partial exchange of the contents between it and its adjacent
higher and lower located segments of intestine. This significantly reduces the reproducibility of the
results obtained and makes it difficult to interpret them [3].
Recently, we have created a new method based on the existence of a correlationbetween the rate
of free consumption of concentrated glucose solution by fasting rats and the ability to absorb it in
small intestine. This method allowsus to get a quantitative, although indirect,assessmentofthelevelof
absorption of glucose in the small intestine in animals under natural conditions, without influence of
anesthesia and any surgical manipulation [4].
Each
of
the
existing
methods
of
research
has
its
advantagesandlimitations,
mutuallycomplementing each other. The effectiveness and expediency of their application is
determined by the specific tasks facing the researcher.
399
Do'stlaringiz bilan baham: |
