Changes of L-arginine-NO pathway in platelets of microvascular angina patients and reversing effects of intravenous L-arginine infusion on L-Arg-NO transport / 第二军医大学学报

ABSTRACT

Objective: To observe the L-Arg (L-arginine) transport, the nitric oxide (NO) production, and NO synthase (NOS) activity in platelets, investigate the significance of the L-Arg-NO system in the pathogenesis of microvascular angina (MVA), and to study the reversing effects of intravenous L-Arg infusion on L-Arg transport. Methods: The 3H-L-Arg transport, NO production, and NOS activity in platelets were examined in 15 patients with MVA and 15 healthy controls. The 15 patients were given intravenous L-Arg infusion (20 g/d) after basic physical examination and were examined again 10 days later. Results: The L-Arg transport in platelets of MVA patients was obviously lower than that in the normal group; the maximum transport velocity (Vmax) decreased by 34. 4% compared with the normal group (P<0.01); and the Michaelis constant (Km) increased by 21.4% (P<0.05). The production of NO2- and the activity of NOS in platelets were decreased by 47.1% (P< 0.05) and 25.4% (P<0.05) compared with the normal group, respectively. Intravenous L-Arg infusion reversed the above changes in MVA patients; it increased the Vmax by 11.9% (P<0.01) and decreased Km by 18% (P<0.05); it also increased production of NO2- by 1.33 folds (P<0.05) and NOS activity by 1.2 folds (P<0.05). Especially, the attack of angina and patient ECG were greatly improved after intravenous L-Arg infusion. Conclusion: L-Arg-NO pathway is impaired in MVA patients, which might be responsible for the endothelium-dependent vascular relaxation in MVA patients. Intravenous L-Arg infusion may benefit the impaired function of L-Arg-NO transport in patients with MVA.