[Effect of proteasomal proteolysis on NO-synthase activity in isolated platelets].

: In experiments with isolated platelets it was shown, that application of proteasomal fraction II (PF II) from rabbit's reticulocytes changes the activity of endothelial nitric oxide synthase (eNOS). During incubation of sonicated platelets with PF II eNOS activity increased by 24.6% (p = 0.02). Methylated ubiquitin and clasto-lactacystin beta-lacton significantly eliminated this effect. So, it is not eNOS that is subsequent to proteasomal degradation, but a certain negative regulator of its activity. eNOS activity in platelets, treated with H2O2 (1 mM), after incubation with PF II increased to a higer extent, and was 3.4 +/- 0.36 UF/min x 10(6) cells (for 51.3% more, than in control), but H2O2 did not affect the activity of enzyme in platelets under analogous condition without addition of PF II. It was established, that eNOS activity decreases after 60 min of incubation with 10 mM of clasto-lactacystin beta-lacton by 11.6%, and with 20 mM--by 28.6% (p < 0.05). Data obtained witnesses about participation of ubiquitin-dependent proteasomal proteolysis in regulation of eNOS activity and possibility of the effect upon intensity of NO production due to acceleration of degradation of intracellular regulators of this enzyme's activity.