Platelet activation after adrenergic stimulation in hypertensive patients: effects of acebutolol

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Blood platelets in human essential hypertension

Blood platelets of patients with essential hypertension display signs of both increased sensitivity in vitro to aggregating stimuli believed to contribute to thrombosis and of activation in vivo possibly expressing the release of vasoactive products. The mean features of the modified platelet profile in hypertension include an increased alpha 2-adrenergic receptor density, an enhanced rate of adhesion/aggregation in particular in response to ADP and arachidonic acid, a greater sensitivity for thrombin and adrenaline to stimulate increases in cytoplasmic-free Ca2+, increased resting levels of cytoplasmatic-free Ca2+, a reduced content of serotonin often combined with a defective uptake mechanism, a facilitated efflux rate of noradrenaline, an exaggerated release reaction in vivo as indicated by the increased plasma levels of Beta-thromboglobulin and a shortened platelet life span. These changes occur to various extents in some, but not all, hypertensive patients and are not always strictly related to the degree of blood pressure increase. On the contrary, platelet cyclooxygenase and thromboxane synthetase activity are in the normal range.