Effects of 2-hydroxyestradiol on the number of granulosa cell beta-adrenergic receptors.
Recent studies have shown that 2-hydroxyestradiol (2-OH-E2) synthesized locally from estradiol (E2) stimulates progesterone production by granulosa cells (GC) and enhances the action of other trophic hormones. A particularly strong synergistic interaction between 2-OH-E2 and beta-adrenergic agonists was observed. Therefore, the present studies were undertaken to determine if this synergism was due to a 2-OH-E2-stimulated increase in the number of beta-adrenergic binding sites in GC. Binding of the 125I-labeled beta-adrenergic ligand iodocyanopindolol ([125I]iodo-CYP) to GC was evaluated and was found to be saturable with time and ligand concentration, and of high affinity (Kd = 29 +/- 8 pM; maximum binding = 0.55 +/- 0.02 fmol/10(6) cells). Rank order potency for agonist/antagonist binding was consistent with a beta-adrenergic receptor: propranolol greater than isoproterenol greater than norepinephrine. 2-OH-E2 did not compete for the [125I]iodo-CYP-binding sites. Incubation of cultured porcine GC with 2-OH-E2 caused a time- and dose-dependent increase in the number of specific [125I]iodo-CYP-binding sites. Averaged over eight separate experiments, 4-day treatment with 4 micrograms/ml 2-OH-E2 increased the number of [125I]iodo-CYP-binding sites 3.1 +/- 0.9-fold above the control value (P less than 0.05). A similar 4-day treatment with 2 micrograms/ml E2 or 200 ng/ml LH or FSH was without effect on [125I]iodo-CYP binding (P greater than 0.05) despite stimulation of progesterone secretion to a degree similar to that seen with 2-OH-E2. These results support the hypothesis that 2-OH-E2 produced by GC may enhance progesterone production stimulated by catecholamines, in part by increasing the numbers of beta-adrenergic binding sites on GC.
Spicer
L J
LJ
Department of Medicine, Milton S. Hershey Medical Center, Pennsylvania State University, Hershey 17033.
Hammond
J M
JM
D000818:Animals; D001667:Binding, Competitive; D002478:Cells, Cultured; D004958:Estradiol / Q000031:analogs & derivatives* / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D007986:Luteinizing Hormone / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011433:Propranolol / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D013552:Swine
D011943:Receptors, Adrenergic, beta; D004958:Estradiol; D020120:Iodocyanopindolol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D011433:Propranolol; C001390:2-hydroxyestradiol; D010869:Pindolol; D007545:Isoproterenol; D009638:Norepinephrine