Adrenergic receptors in bovine retinal microvessels: presence of alpha 2- and beta- but not alpha 1-receptors.
In bovine retinal microvessels, alpha 1, alpha 2- and beta-adrenergic receptors were characterized by binding assay, using [3H]prazosin, [3H]para-aminoclonidine and [125I]iodocyanopindolol as radioligands, respectively. The microvessels were purified from bovine eyes by differential centrifugation through a high concentration of bovine serum albumin followed by use of a glass bead filtration technique. In the preparation, specific binding sites for [3H]para-aminoclonidine and [125I]iodocyanopindolol were observed, whereas [3H]prazosin binding was not detected. The [3H]para-aminoclonidine binding sites localized to the microvessels were characterized by high affinity and saturability (KD: 173 +/- 9 pM; Bmax: 394 +/- 11 fmol/mg protein) as well as the [125I]iodocyanopindolol binding sites (KD: 20 +/- 3 pM; Bmax: 43 +/- 4 fmol/mg protein). Furthermore, the specificity of both binding sites was pharmacologically evaluated by measuring the inhibitory effects of various adrenergic reagents on binding. The existence of alpha 2- and beta-adrenergic receptors which were characterized by high affinity, saturability and stereospecificity, leads to the hypothesis that the retinal microcirculation is under neuronal control.
Kobayashi
H
H
Department of Pharmacology and Ophthalmology, University of Occupational and Environmental Health, Japan, School of Medicine, Kitakyushu.
Iwasaki
T
T
Izumi
F
F
Kurimoto
S
S
D000818:Animals; D002417:Cattle; D008833:Microcirculation / Q000032:analysis; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D012171:Retinal Vessels / Q000032:analysis*
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta