INCREASE IN Ca2+,Mg2+-ATPase ACTIVITY OF CELLS AS ONE OF THE MECHANISMS OF ANTIPROLIFERATIVE EFFECT OF MITOMYCIN C IN THE TREATMENT OF URETHRA STRICTURE

Abstract

Introduction. In the clinic, the antiproliferative activity of mitomycin C is used to prevent the formation of scars in tissues, since scar changes are one of the complications of surgical interventions. In urology, strictures of the urethra are quite common, in particular, it is associated with catheterization, transurethral surgery, urinary tract infection, and injuries. Relapses after unsuccessful urethroplasty are 18–40 %.

The aim of the study – to investigate the effect of mitomycin C on the Ca²⁺,Mg²⁺-ATPase activity of the plasma membrane and endoplasmic reticulum membranes of peripheral blood lymphocytes.    

Research Methods. The study was conducted on peripheral blood lymphocytes of practically healthy men, as lymphocytes are considered the "metabolic mirror" of the body and promptly respond to all external and internal influences. Determination of the total Ca²⁺,Mg²⁺-ATPase activity of blood lymphocytes was carried out at 37 °C in the incubation medium of the following composition (mM): 150 KCl; 0.05 CaCl₂; 5 MgС1₂; 5 ATP; 1 NaN₃ (mitochondrial ATPase inhibitor); 1 ouabain (inhibitor of Na⁺,K⁺-ATPase); 20 Hepes-Tris buffer (pH = 7.4). To separate the total Ca²⁺,Mg²⁺-ATPase activity into components: thapsigargin-insensitive Ca²⁺,Mg²⁺-ATPase of the plasma membrane (PM) and thapsigargin-sensitive Ca²⁺,Mg²⁺-ATPase of the reticulum membranes (SER) were added to the standard Ca²⁺- and Mg²⁺-containing incubation medium SER Ca²⁺,Mg²⁺-ATPase inhibitor – thapsigargin (0.1 µM).

Results and Discussion. Under the influence of different concentrations of mitomycin C, the amount of Ca²⁺,Mg²⁺-ATPase activity of PM increased dose-dependently and was the highest at a concentration of 10^-3 M (3.98±0.42) μmol Pi/min per 1 mg of protein (р<0.05), i.e. 1.36 times. The thapsigargin-sensitive component of the Ca²⁺,Mg²⁺-ATPase of lymphocytes in the control was (2.19±0.27) μmol Pi/min per 1 mg of protein, and with an increase in the concentration of mitomycin C in the incubation medium it increased to (2.97±0, 29) μmol Pi/min per 1 mg of protein (p<0.05), i.e. 1.35 times. The initial maximum rate of ATP hydrolysis by Ca²⁺,Mg²⁺-ATPase PM and SER of lymphocytes under the action of 10^-3 M mitomycin C increased by 1.3 times.

Conclusions. An increase in the Ca²⁺, Mg²⁺-ATPase activities of the plasma membrane and endoplasmic reticulum under the influence of mitomycin C indicates that it can prevent overloading of the cytosol with Ca²⁺ ions and, thus, inhibit proliferative processes and the formation of strictures. An increase in the activity of Ca²⁺,Mg²⁺-ATPase PM and SER membranes of blood lymphocytes occurs due to an increase in the number of revolutions of the enzyme, but not due to an increase in affinity to the substrate.