Functional relationship between platelet alpha 2-adrenoceptors and sympathetic nerve activity in man.
Functional relationships between platelet alpha 2-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 less than 0.01) to resting plasma NE and negatively (r = -0.531, p less than 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 alpha 2-adrenoceptor density is functionally regulated in parallel with sympathetic nerve activity rather than plasma NE per se. This hypothesis seems quite reasonable when it is extended to the presynaptic alpha 2-adrenoceptors; otherwise, the negative feedback function on NE release should be lessened and contradictory to its physiological role.
Noshiro
T
T
Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Miura
Y
Y
Kimura
S
S
Meguro
Y
Y
Sugawara
T
T
Ohashi
H
H
Takahashi
M
M
Sano
N
N
Watanabe
H
H
Ohzeki
T
T
D000328:Adult; D001792:Blood Platelets / Q000378:metabolism*; D004837:Epinephrine / Q000097:blood; D006801:Humans; D006929:Hyperaldosteronism / Q000097:blood / Q000378:metabolism; D006973:Hypertension / Q000097:blood / Q000378:metabolism*; D009638:Norepinephrine / Q000097:blood; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D012016:Reference Values; D013564:Sympathetic Nervous System / Q000378:metabolism*; D013565:Sympatholytics / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D013565:Sympatholytics; D009638:Norepinephrine; D004837:Epinephrine