Characterization of platelet hypofunctions in rats under SART stress (repeated cold stress)

Platelet hypoaggregability has been reported in rats exposed to a chronic form of environmental stress induced by long-lasting fluctuation in air temperature, known as SART (specific alternation of rhythm in temperature) stress. This study examines functional characteristics of platelets from stressed rats in more detail. Exposure to stress reduced aggregation and ATP release in platelets stimulated with collagen, as determined using platelet-rich plasma (PRP). The resting levels of ATP but not ADP in platelets from stressed rats were lower than those from unstressed ones. Collagen-induced release and resting level of serotonin also decreased in platelets from stressed rats. In contrast, stress failed to cause hypoaggregability of washed platelets. Circulating platelet aggregates were detected in stressed rats. From these data, SART stress appears to cause intravascular activation of platelets in spite of in vitro hypofunctions. Alteration in plasma milieu may be associated with stress-induced platelet hypofunctions in PRP.