[Restraint stress down-regulates L-Arg/NOS/NO pathway of platelet and aortic intima in rats].

Objective: To investigate alteration and cross link of the aortic intima and platelet endogenous L-Arg/NOS/NO pathway induced by water immersion restraint (WIR) stress.
Methods: After 7 h of WIR stress, the aortic intima was isolated and prepared the platelet, then NO2- production released from aortic intima and platelet was measured with Greiss regent, NOS activity and L-arginine transport activity were detected by isotope tracer method.
Results: After 7 h of WIR stress, the levels of NO2- from platelet and aortic intima obviously decreased by 57% and 46% respectively as compared with the control rats (P<0.01). The inhibitory effects of NO2- showed a positive correlation between platelet and aortic intima by person regression analysis (r2=0.9835, P<0.01). The kinetics analysis of NOS activity of platelet showed that the enzymatic catalytic maximum velocity (Vmax) decreased by 44%, Km values increase by 18% and the enzymatic catalytic efficiency was obviously reduced in the WIR stress rats (P<0.01). The aortic intima NOS activity was inhibited by 50% after WIR stress (P<0.01). The person analysis showed the obvious correlation between them (r2=0.9726, P<0.01). In the WIR stress platelet, the L-Arg transport Vmax obviously reduced by 32%, Km parameter increased 37%, and the transport efficiency was inhibited by 50% (P<0.01), which exhibited obvious positive correlation with the inhibition of L-Arg transport activity in aortic intima (27%) of WIR stress rats (r2=0.9887, P<0.01).
Conclusion: WIR stress down-regulated endogenous L-Arg/NOS/NO pathway of aortic intima and platelet, whose alteration showed obvious positive correlation. Detection of the alteration of endogenous L-Arg/NOS/NO pathway in platelet might act as an indirect method to assess the endothelial dysfunction involving the pathogensis of stress.