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 sc reening blood pressure were randomized to prolonged mental stress by r eceiving a letter informing of a high screening blood pressure (n = 13 ), or a neutral letter (n = 13). Blood platelet function in vive was a ssessed by measurements of plasma concentrations of the platelet-speci fic protein beta-thromboglobulin, platelet counts, and mean platelet v olumes before and during two laboratory stress tests (hand cold presse r test and arithmetic challenge). The cold presser test caused a signi ficant increase in beta-thromboglobulin concentrations in both groups, and significantly more in the uninformed group. Platelet count increa sed significantly in both groups during mental arithmetic with signifi cantly higher counts in the uninformed group. Overall plasma beta-thro mboglobulin responses were significantly larger in the uninformed grou p. This study demonstrates that laboratory stress is associated with b lood platelet activation and that awareness of high blood pressure att enuates the platelet responses to such stress tests.