Blood platelet responses to laboratory stress in young men The effect of awareness of high blood pressure

Healthy 19-year old males from the 95th percentile of mean arterial screening blood pressure were randomized to prolonged mental stress by receiving a letter informing of a high screening blood pressure (n = 13), or a neutral letter (n = 13). Blood platelet function in vivo was assessed by measurements of plasma concentrations of the platelet-specific protein β-thromboglobulin, platelet counts, and mean platelet volumes before and during two laboratory stress tests (hand cold pressor test and arithmetic challenge). The cold pressor test caused a significant increase in β-thromboglobulin concentrations in both groups, and significantly more in the uninformed group. Platelet count increased significantly in both groups during mental arithmetic with significantly higher counts in the uninformed group. Overall plasma β-thromboglobulin responses were significantly larger in the uninformed group. This study demonstrates that laboratory stress is associated with blood platelet activation and that awareness of high blood pressure attenuates the platelet responses to such stress tests.