Alpha 2-adrenoceptors and I1-imidazoline binding sites: relationship with catecholamines in women of reproductive age.
A comparison is presented between plasma catecholamine concentrations and platelet [125I]-p-iodoclonidine binding sites in 16 healthy women. Blood samples were obtained at six regularly spaced intervals over two consecutive menstrual cycles from healthy women with regular menstrual periods. Although no cycle-related changes were observed per se, there were significant correlations between the platelet binding sites and plasma norepinephrine and epinephrine concentrations. The densities of platelet alpha 2-adrenoceptors were negatively correlated in an exponential fashion (r2 = 0.694, P = 0.009) with plasma epinephrine concentrations, implying agonist-induced downregulation. On the other hand, platelet I1-imidazoline binding sites were positively correlated with plasma concentrations of norepinephrine in a linear fashion (r2 = 0.326, P = 0.021). This is the first indication that I1 binding sites might be upregulated by a physiological factor. Furthermore, the data suggest that elevations in plasma norepinephrine might explain reports of upregulated I1 binding sites in depressed patients.
Department of Psychiatry, University of Mississippi Medical Center, Jackson 39216-4505, USA.
J E
JE
Piletz
M
M
Andrew
H
H
Zhu
Y Z
YZ
Feng
J
J
Rains
A
A
Halaris
D000328:Adult; D001792:Blood Platelets / Q000378:metabolism; D003000:Clonidine / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D004837:Epinephrine / Q000097:blood*; D005260:Female; D006801:Humans; D054755:Imidazoline Receptors; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics*; D008597:Menstrual Cycle / Q000502:physiology*; D009638:Norepinephrine / Q000097:blood*; D011869:Radioligand Assay; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology*; D011955:Receptors, Drug / Q000502:physiology*; D012016:Reference Values; D015854:Up-Regulation / Q000502:physiology
D054755:Imidazoline Receptors; D007457:Iodine Radioisotopes; D018341:Receptors, Adrenergic, alpha-2; D011955:Receptors, Drug; C053113:4-iodoclonidine; D003000:Clonidine; D009638:Norepinephrine; D004837:Epinephrine