Characteristics of β-adrenergic receptors in longitudinal muscle membranes of rat uterus: Changes in kinetic properties of the receptor during gestation

✍ Scribed by Yuji Kaneko; Takuji Tsukamoto; Tatsuhiko Kawarabayashi; Masahiko Ikeda; Hajime Sugimori

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 579 KB
• Volume: 9
• Category: Article
• ISSN: 0952-3499
• DOI: 10.1002/(sici)1099-1352(199605)9:3<233::aid-jmr264>3.0.co;2-#

✦ Synopsis

Binding characteristics of P-adrenergic receptors of longitudinal muscle membranes isolated from different stages of pregnant rat myometrium were investigated using [%]dihydroalprenolo1. Between Days 15 and 21 of gestation, the ratio of /3,and &-adrenergic receptors of longitudinal membranes was constant. The membranes were found to be predominant in h-adrenergic receptors. The concentration of longitudinal muscle p-adrenergic receptors increased significantly during the last 7 days of gestation. Kinetic binding studies implied that the affinity of the membrane Padrenergic 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 P-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 I3H] DHA binding to &receptors of muscle on Day 21 suggested the existence of negatively cooperative multiple binding sites for fl-adrenergic ligand. These results suggest that changes in the dynamics of uterus Padrenergic receptors play an important role in the onset of labor.