[Signal transudation pathways in parietal cells of the gastric mucosa in experimental stomach ulcer].

The goal of the presented work was the research of signal transduction mechanism in the rat gastric parietal cells under stomach ulcer conditions. In these cells activation of adenylate cyclase (increase of cAMP level and proteinkinase A activity) and phosphoinositide (increases [Ca2+]i; cGMP and phoshatidylinocitole levels; proteinkinase C, proteinkinase G, and calmodulin-dependent-proteinkinase activity) of signals pathway was shown. An increase of plasma membrane phospholipids (PC, PS, PE, PI, LPC) level was shown. Under conditions of influence of the stress factor the membran enzymes activity (H+, K+ -ATPase, 5'-AMPase, Na+, K+ -ATPase, Ca2+, Mg2+ -ATPase and H+, K+ -ATPase) was considerably increased. The intensification of lipid peroxidation processes in rats was demonstrated.

[Functioning of tyrosine protein kinases and phosphatases in gastric mucosa cells under conditions of oxidative and nitrosative stress in gastric lesions].

Acute cold stress caused lesions of gastric mucosa as a result of its attack by active oxygen and nitrogen compounds. The tissue regeneration is regulated by a cascade of tyrosine protein kinases. Gastric ulceration leads to a decrease in activity of tyrosine protein kinases and phosphatases, following by fall in phosphotyrosine content in proteins of plasma membranes of gastric mucosa cells. No changes in superoxide dismutase activity, slight increase in catalase activity, inhibition of glutathione peroxydase, significant increase in OH* content and decrease in zinc level were observed in the gastric mucosa cells of stressed rats. That increased oxidative damage can lead to inactivation of protein tyrosine phosphatases. Nitric oxide synthase activity was three times higher in gastric mucosa cells after the cold stress. That can promote nitrosylation of tyrosine residues. During following days nitric oxide synthase activity remains high. Superoxide dismutase is activated on the 4 and 5th day after the stress. Catalase activity normalizes after second day. Tyrosine protein kinase activity increases in membranes with maximum on the 4th day, and remains inhibited in cytosole. Tyrosine protein phosphatases keep inhibited as well. Gluthatione peroxydase activity and zinc level decreased on the 5th day. Obtained results can be the evidence of violations in signal transduction through protein tyrosine kinase cascades, due to the reduction in tyrosine phosphorylation, as a result of increase in the content of active oxygen and nitrogen species.

[Regulation of secretory processes in parietal cells in the different stomach pathologies].

This review deals with the analysis of the modern literature concerning molecular mechanisms of secretory activity of gastric mucosa cells and their importance during development of different pathologies. Gastric acid secretion is regulated by paracrine, endocrine and neural systems. The result of these systems functioning at the molecular level is signal transduction pathways activation by histamine, acetylcholine, gastrin and other mediators. Coupling of these agents with specific receptors located on the basolateral plasma membrane of parietal cells modulates acid secretion. It was shown that protein phosphorylation enzymes play the significant role in realization of functional and proliferative activity of the stomach secretory cells in physiological and pathological states. The key role of tyrosine protein kinases associated with growth factors is considered, which take part in regulation of acid secretion, have trophic influence on mucosa cells, protect it from acute injuries, stimulate cell proliferation and accelerate ulcer healing.

[Peculiarities of dephosphorylation reaction catalyzed by purified protein tyrosine phosphatase CD45 from thymocytes of intact and exposed to ionising radiation rats].

This paper is devoted to analysis of parameters of catalytical activity of CD45, the major transmembrane proteintyrosine phosphatase (PTP-ase) of the lymphocytes, isolated from plasma membranes of thymocytes of control and 0.5 Gy irradiated rats. CD45 catalytic features were evaluated using 0.2 mM sodium vanadate as the inhibitor and paranitrophenylphosphate (1-8 mM) and phosphotyrosine (1-6 mM) as, respectively, nonspecific and specific substrates. With the former, irradiation was shown to cause a decrease in Vmax but an increase in affinity. With phosphotyrosine both Vmax and affinity decreased. These data suggest that the exposure to radiation causes an increase in non-specific enzyme activity with a decrease in the ability to dephosphorylate the specific substrate. A study of cooperativity parameters shows that cooperativity between two phosphatase domains increased after irradiation. An analysis of the inhibitor kinetics showed that radiation caused a change of competitive inhibition by mixed one.

[Role of the protein tyrosine phosphatase CD45 in signal transduction of hematopoietic cells]. / Rol' proteïntyrozynfosfatazy CD45 u syhnal'nii transduktsiï klityn hematopoetychnoho riadu.

This review deals with the analysis of modern literature about structure, catalytical activity, biological role and practical usage of protein tyrosine phosphatase CD45, which is widely distributed in the membranes of hematopoietic cells. The enzyme location makes it a highly sensitive test for estimation of development of such pathological states as immunological and neoplastic diseases, malignant tumors and transplantation responses of tissue tearing away. Unequal enzyme isoforms expressed in various leucocyte cell lines at different stages of development and differentiation are typical of those species. The existence of multiple isoforms is not used only to determine various cell lines, but also causes existence of variable adhesion requirements resulting in local restriction of activity and changes in the substrate binding. There is no doubt that definition of substrate molecules, influence of proteintyrosinephosphatase CD45 translocation and regulation of its activity by other ligands are important questions. Solution of these problems will be useful for searching the correctional means of dysfunctions of the tissues, enriched with protein tyrosine phosphatase CD45.