Platelet Characteristics Change With Aging: Role of Estrogen Receptor β

Estrogen receptor beta (βER) is the predominant estrogen receptor in platelets. Experiments were designed to define phenotypic changes in platelets with aging following deletion of βER (βERKO). Blood was collected from wild-type and βERKO female mice at 4–7 (young) and 24–25 (aged) months of age. In young animals, total number of platelets, number of platelets containing RNA (reticulated platelets), aggregation, dense body adenosine triphosphate secretion, and alpha granular secretion were the same in both groups. With aging, total number of platelets decreased but reticulated platelets increased in βERKO mice; aggregation and dense granule adenosine triphosphate secretion decreased whereas basal expression of fibrinogen receptors increased with age in wild-type and βERKO mice. Basal expression of P-selectin and annexin V binding increased with aging only in βERKO mice; thrombin did not increase expression in these mice. Therefore, deletion of βER is associated with specific platelet functions, which are expressed only with age-associated reproductive senescence.