Characteristics of beta-adrenergic receptors in longitudinal muscle membranes of rat uterus: changes in kinetic properties of the receptor during gestation.
Binding characteristics of beta-adrenergic receptors of longitudinal muscle membranes isolated from different stages of pregnant rat myometrium were investigated using [3H]dihydroalprenolol. Between Days 15 and 21 of gestation, the ratio of beta 1- and beta 2-adrenergic receptors of longitudinal membranes was constant. The membranes were found to be predominant in beta 2-adrenergic receptors. The concentration of longitudinal muscle beta-adrenergic receptors increased significantly during the last 7 days of gestation. Kinetic binding studies implied that the affinity of the membrane beta-adrenergic receptors decreased through a slight decrease in the association rate and a large increase in the dissociation rate with progression of pregnancy. A Scatchard plot indicated that longitudinal muscle in beta-adrenergic receptors on Days 15 and 18 constitute a single class of independent sites. By contrast, the dissociation kinetics, the convex downward curvature in a Scatchard plot and a Hill coefficient (h) of less than 1.00 of [3H] DHA binding to beta-receptors of muscle on Day 21 suggested the existence of negatively cooperative multiple binding sites for beta-adrenergic ligand. These results suggest that changes in the dynamics of uterus beta-adrenergic receptors play an important role in the onset of labor.
Kaneko
Y
Y
Department of Applied Biological Sciences, Saga University, Japan.
Tsukamoto
T
T
Kawarabayashi
T
T
Ikeda
M
M
Sugimori
H
H
D000319:Adrenergic beta-Antagonists / Q000378:metabolism; D000818:Animals; D004082:Dihydroalprenolol / Q000378:metabolism; D005260:Female; D007700:Kinetics; D009215:Myometrium / Q000737:chemistry* / Q000648:ultrastructure; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018342:Receptors, Adrenergic, beta-1 / Q000032:analysis* / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000032:analysis* / Q000378:metabolism
D000319:Adrenergic beta-Antagonists; D018342:Receptors, Adrenergic, beta-1; D018343:Receptors, Adrenergic, beta-2; D004082:Dihydroalprenolol