Functional Relationship Between Platelet α2-Adrenoceptors and Sympathetic Nerve Activity in Man

Functional relationships between platelet α2-adrenoceptors and sympathetic nerve activity were studied in patients with essential hypertension (n=23), primary aldosteronism (n=10), and normal subjects (n=12). The maximum number of binding sites (Bmax) and the dissociation constant (Kd) of 3H-yohimbine on platelet membranes and resting plasma norepinephrine (NE) were similar among these groups of subjects. In all subjects combined, Bmax values were correlated positively (r=0.471, p<0.01) to resting plasma NE and negatively (r=-0.531, p<0.01) to the changes in plasma NE when subjects were moved from lying to standing. A 2–4 week treatment with guanabenz or bethanidine induced a parallel fall of both Bmax and plasma NE, whereas administration of reserpine caused a similar fall of plasma NE but Bmax remained unchanged. Kd values were not changed after any of these treatments.The results support the view that platelet α2-adrenoceptor density is functionally regulated in parallel with sympathetic nerve activity...