Effects of acute and chronic hypoxia exercise on erythrocyte aggregation and binding of fibrinogen to erythrocyte under shear flow

Pathological erythrocyte aggregation reduces capillary perfusion and oxygen transfer to tissue, resulting in tissue ischemia or infraction. This study investigates how hypoxic exercise training affects erythrocyte aggregation and binding affinity of fibrinogen to erythrocyte. Fifteen sedentary healthy men cycled on an ergometer at about 60% of maximal oxygen consumption under 15%O 2 condition for 40 minutes per day, 5 days per week for 5 weeks. The erythrocyte aggregation and binding affinity of fibrinogen to erythrocyte were measured by ektacytomety and flow cytometry, respectively. Our results demonstrated that at pre‐training stage, acute 12%O 2 exercise increased erythrocyte count, as well as, shortened critical time and heightened critical shear stress in erythrocyte aggregation under conditions of whole blood and the isotonic 1% solution of dextran 500. However, 5 weeks of 15%O 2 exercise training attenuated the enhancement of erythrocyte aggregability caused by acute 12%O 2 exercise. Additionally, although shear stress disassociated the fibrinogen adhesion to RBC surface in an intensity‐dependent manner, hypoxic exercise did not influence the ability of shear‐disassociated interaction between fibrinogen and erythrocyte. Therefore, we conclude that long‐term moderate‐intensity exercise at 15%O 2 environment suppresses erythrocyte aggregation but not changes the binding affinity of fibrinogen to erythrocyte following severe hypoxic exercise.