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Male Wistar rats were fed selenium (0.2, 2.9 or 5.5 mg/kg of dry feed) in the form of selenomethionine. They also received for 6 weeks amidopyrine (33 mg/kg b.w.) and/or sodium nitrite (20 mg/kg b.w.) administered intragastrically. The quantitation of endogenously synthetized volatile nitrosamines in the stomach, selenium in the serum, biochemically evaluated nitrite and nitrosamines toxicity revealed an inverse relationship between feed selenium concentrations and the amount of endogenously produced nitrosodimethylamine from equal precursor doses. A protective selenium effect on methemoglobin-producing action of nitrite ions was established. It is shown that introduction of precursors induces increased body need in selenium.

The administration to rats of radioactive preparations. 75Se- selenomethionine, 35S-methionine or sodium 75Se-selenite in the amounts creating the absorbed dose in the body of 0.5 Gy suppressed the delayed hypersensitivity reaction as was registered 1-12 months after the injection. The delayed hypersensitivity was tested in vitro by the method of inhibimacrophage spreding inhibition. The degree of suppression of the cellular immune response depended upon the type of the compound administered, of which the radionuclide was a component, and upon characteristics of radiation spectrum of the radionuclide.

In experiments on CBA mice it was shown that migration of 51Cr-labeled spleen lymphocytes, injected intravenously, to lymph nodes of intact recipients was suppressed 6-24 months after the administration of a radiopharmaceutic preparation of selenium-75-selenomethionine in a quantity forming the doses of 1 Gy and 1.5 Gy absorbed within the whole body and lymphoid organs, respectively. Migration of labeled lymphocytes to the liver, kidneys and lungs, as well as their retention in the circulating blood, were increased. As the result of the migration disorders the specific affinity of lymphocytes for peripheral lymphoid tissue decreased.

Gamma-topography of the abdominal region and radiometry of duodenal aspirates were used for examination of 707 patients with different gastroenterological pathology using various modes of the administration of 75Se-methionine (intravenously, per os, into the duodenal and cecal lumens, intra-arterially in the celiac trunk and superior mesenteric artery). The RP administered intravenously was accumulated in health in the liver and pancreas. The drug fixation by the proximal part of the jejunum was also typical of chronic pancreatitis, the degree of fixation being well correlated with a period of disease. A jejunum image on gamma-topograms proved to be determined not by radioactivity of the jejunum in passage of labeled pancreatic juice but by extraction of the radionuclide from the blood by its wall. In transduodenal administration of the radionuclide its major part was rapidly absorbed and accumulated in the liver. At the same time a considerable part of the drug remained at the site of administration and retained there for several days. There was almost no absorption of the drug in the cecum and ascending colon. Like in the duodenum, the drug retained at the site of administration for a long time. Intestinal extravasal trophicity was assumed.

Following single administration of 75Se-methionine to female rats, adenomas of hypophysis were revealed in these, after some delayed periods of time. The tumors developed on the background of a high level of estradiole in the rat's blood. With the electron microscope these tumors were differentiated as prolactionomas. It has been shown that the increase in the number of prolactin-producing cells is due mainly to chromophobic cell differentiation, in addition to the stomatotrophocyte transformation under a long-term hyperestrogenization of the organism.

At later times after the injection of selenium-75-selenium methionine to CBA mice the inhibition of migration of intravenously injected normal 51Cr lymphocytes to the lymph nodes and liver lasted for a long time. On the contrary, no changes in the normal lymphocyte migration within the animal body were observed after total-body gamma-irradiation with the dose of 4 Gy. The data obtained are indicative of the radiation-induced disturbance of the microenvironment factors, which provide migration of lymphocytes within the body, during the long-term exposure to radiation emitted by the incorporated source.