Properties of Na+,k+-activated, Mg2+-dependent ATP-hydrolyze of blood lymphocytes in patients with reаctive arthritis

A significant role in the development and course of reactive arthritis (ReA) is played by T-lymphocytes as their development and systemic manifestations are based on immunological mechanisms. Additionally, the pathogenesis of many diseases is linked to changes in the structure and function of ion-transporting systems. Therefore, the aim of the study was to find out the kinetic properties of ATP-hydrolysis reaction involving Na+,K+-ATPase of peripheral blood lymphocytes of healthy individuals and patients with ReA. We used the current methodological approaches to the study of ATPase activity in saponin permeabilized cells. We conducted an analysis of the kinetic properties of ouabainsensitive Na+,K+-ATPase activity of saponin-perforated peripheral blood lymphocytes of healthy donors and patients with rheumatoid arthritis (RеA). We found out that in peripheral blood lymphocytes of patients with RеA primary active transport of Na+, K+ ions is slower and less intensive, though characterised by the same capacity, as in healthy donors. The affinity constant for ATP in peripheral blood lymphocytes in patients with RеA is greater by 2.9 times than its value in comparison with healthy donors. We established that in conditions of rheumatic pathology in immunocompetent cells, inhibition of Na+,K+-ATPase activity is not caused by reduction of speed of enzyme work, but by increase of affinity of ouabainsensitive Na+,K+-ATPase to ATP. At the same time, the Mg2+-binding center of Na+,K+-ATPase in patients with RеA is endogenous. We also found that affinity Na+,K+-ATPase to the ions K+ in peripheral blood lymphocytes of healthy donors is 2.4 times higher than in patients  with RеA. We observed that Na+,K+-ATPase of peripheral blood lymphocytes of patients with RеA retains its endogenous receptor properties – sensitivity to ouabain does not change. It is assumed that under conditions of rheumatic pathology the impact on the Na+,K+-ATPase structure occurs both externally and on the cytoplasmic membrane surface. The above experimental data can be used for further clarification of the membrane mechanisms of ion exchange in immunocompetent cells of patients suffering from autoimmune diseases.