Summary
The influence of the sympathetic nervous system on platelet functions in vivo is still
controversial. The aims of our study were to compare the response to various sympathetic
stimuli in normal subjects and in patients with essential hypertension (HT) or peripheral
vascular disease (PVD) and to evaluate any correlations among plasma levels of catecholamines,
beta-thrombo-globulin (β-TG) and platelet factor 4 (PF4). In basal conditions β-TG
and PF4 values in the HT patients were higher than those observed in the controls
of the same age but lower than those of the PVD patients. Although the different sympathetic
stimuli (90° tilting, handgrip, treadmill test, bicycle test) caused a significant
increase of the plasma epinephrine (E) and norepinephrine (NE) levels, they did not
modify the β-TG and PF4 levels in any of the groups studied. The platelet activation
indices, therefore, regardless of the basal values, do not seem to be influenced by
sympathetic stimulation.