Effects of chronic exercise and deconditioning on platelet function in mid-follicular females

To investigate the effects of chronic exercise and deconditioning on platelet function in mid-follicular females, 16 healthy sedentary women were divided into control and exercise groups. The exercise group started training in the mid-follicular phase on a bicycle ergometer at about 50% V̇_O2max for 30 min/d, 5 d/wk for 2 consecutive menstrual cycles (MCs), then deconditioned for 3 MCs. During this period, platelet functions, including platelet adhesiveness on a fibrinogen-coated surface and ADP-induced aggregation, were measured before and immediately after a progressive exercise test in the mid-folltcular phase. In controls, exercise performance and platelet function were determined at the beginning and 2 MCs later. Besides, ADP-induced intracellular calcium concentration ([Ca²⁺]_i) elevation and cGMP content in platelets, and plasma nitric oxide metabolite levels were measured to clarify possible mechanisms. Our results showed that after training, 1) resting platelet adhesiveness, ADP-induced platelet aggregation and [Ca²⁺]_i elevation were decreased, whereas plasma nitrite/nitrate levels and platelet cGMP contents were enhanced; 2) the increases in platelet adhesiveness, ADP-induced platelet aggregation and [Ca²⁺]_i elevation by acute strenuous exercise were decreased; 3) acute strenuous exercise enhanced plasma nitrite/nitrate levels and platelet cGMP contents to a much larger extent than that before training. Furthermore, deconditioning reversed these training effects back to the pretraining state. These results suggest that female platelet function in the mid-follicular phase can be suppressed by chronic exercise, and be reversed back to pretraining state after deconditioning. These training-induced platelet functional changes may be mediated by nitric oxide.