Alpha-2 adrenergic receptors in the bovine retina. Presence of only the alpha-2D subtype.
OBJECTIVE
To identify and characterize the alpha-2 adrenergic receptor subtypes present in the bovine neurosensory retina.


METHODS
Radioligand saturation and inhibition binding assays were performed with the antagonist radioligands [3H]RX821002 and [3H]rauwolscine.


RESULTS
[3H]RX821002 bound to a single class of receptors with the characteristics of an alpha-2 adrenergic receptor with an affinity (KD) of 0.16 nM and a receptor density (Bmax) of 1500 fmol/mg protein. Correlation of the affinities (pKi values) for nine antagonists in the bovine neurosensory retina with the alpha-2D receptor of the bovine pineal gave a correlation coefficient of 0.99. The correlation coefficients for the alpha-2A (0.84), alpha-2B (0.36), and alpha-2C (0.39) subtypes were much lower. The presence of a minor population of alpha-2B or alpha-2C receptors was excluded.


CONCLUSIONS
A high density of alpha-2D adrenergic receptors is present in the bovine neurosensory retina. Neither the alpha-2B nor the alpha-2C subtype is detectable.
Berlie
J R
JR
Department of Ophthalmology, University of Nebraska Medical Center, Omaha 68198-6260, USA.
Iversen
L J
LJ
Blaxall
H S
HS
Cooley
M E
ME
Chacko
D M
DM
Bylund
D B
DB
D000317:Adrenergic alpha-Antagonists / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D004146:Dioxanes / Q000378:metabolism; D019329:Idazoxan / Q000031:analogs & derivatives; D010870:Pineal Gland / Q000378:metabolism; D011869:Radioligand Assay; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D015016:Yohimbine / Q000378:metabolism
D000317:Adrenergic alpha-Antagonists; D004146:Dioxanes; D018341:Receptors, Adrenergic, alpha-2; D015016:Yohimbine; C058525:2-methoxyidazoxan; D019329:Idazoxan