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Results of numerous researches have revealed that most sensitive to electromagnetic radiations are the nervous, endocrine and cardiovascular systems of an organism, however, the analysis of literary data confirms also the direct involvement of organs of the intestinal system in physiological, and not seldom, and the pathological program of the response of an organism to the action of extreme factors. In the experiment executed on white laboratory male rats by ourselves there was studied the grade of the radiosensitivity of morphoenzymological structural elements of jejunum mucous membrane after 5, 7 and 10 months of chronic influence of electromagnetic fields impulses with a density of induced currents 0.37; 0.7; 0.8; 2.7 kA/m and frequency of impulses 50, 100 and 500 in a week irrespective of their divisibility of ultrashort duration of 15 a 40 ns. Scientific value and novelty of results is concluded in revealed multiple linear relationships between indices of electromagneticfields (duration of the impact, density of induced currents, periodicity of impulses and the dynamics of the studied indices of a morphofunctional condition of a jejunum mucous membrane). Besides that, there was found the critical population to indices of electromagneticfields impulses parameters - the jejunum mast cells differing in hypersensitivity and dependence on duration of influence and density of induced currents revealed, at that their bioeffects were unidirectional.

It was studied the condition of mucous layer of intestine in mice model experiments after ionizing radiation. It were found out the differences in reaction of intestine on radiation in mice at the age of 55 and 95 days. In mice at the age of 55 days at the whole stretch of intestine was marked increased secretion of the polymeric glycoproteins, whereas in mice at the age of 95 days such alterations were marked at smaller degree. In both groups mice was marked increased secretion of bicarbonate after radiation, that is possible to count as characteristic compensative mechanism.

A comparative investigation of transmembrane ion currents and caffeine-induced responses of single smooth muscle cells isolated from the circular layer of rat small intestine was carried out by the method of "patch-clamp". No reliable difference in potential-dependent and amplitude-kinetic characteristics of transmembrane ion currents in cells of intact and irradiated with dose of 3 Gy rats was revealed. In cells of irradiated animals external application of caffeine (4 mM) was not accompanied by strong quick-inactivated transient Ca(2+)-dependent potassium current as in control. The results obtained suggest that single whole-body X-ray irradiation with dose of 3 Gy does not lead in 5 days to any reliable alteration of potential-controlled channels of rat small intestine smooth muscle cell plasma membranes causing at the same time the disturbance of Ca-binding function of intracellular pools.

In studying the influence of cystamine and gammaphos on the recovery of mouse jejunum epithelium after irradiation with doses inducing intestinal form of acute radiation sickness, it was shown that the radioprotective agents did not influence D0 value for intestinal epithelium stem cells, but in crypts the number of DNA-synthesizing enterocytes that entered mitosis increased after the preventive administration of the radioprotectors. All this caused the number of cells per villus to increase and intestinal mucosa to recover more readily.