title: Positive interaction between 17 beta-Estradiol and parathyroid hormone in normal human osteoblasts cultured long term in the presence of dexamethasone.
abstract: We previously developed two models of human osteoblasts with distinct differentiation stages using cells derived from iliac crest trabecular bone explants cultured long term in the presence (HOB + DEX) and absence (HOB - DEX) of 10 nM dexamethasone (DEX) (Wong et al., J Bone Miner Res 1990;5:803). Using these models from 36 subjects aged 41-80 years, we examined the effects of 17 beta-estradiol (E2) on cell proliferation, osteocalcin (OC) production, alkaline phosphatase (ALP) and basal and parathyroid hormone (PTH)-stimulated adenylate cyclase activities, as well as the steady-state mRNA levels of ALP, collagen type I(COLL), OC, and receptors for E2 (ER) and PTH (PTHr). E2 alone had no effect on [3H]thymidine uptake in (HOB - DEX) cells but appeared to stimulate the uptake in (HOB + DEX) cells in a dose-dependent manner, with maximum effect at 10(-10)M (p < 0.05). However, in the presence of 10(-6)M PTH, E2 inhibited the uptake in (HOB - DEX) cells (ANOVA, KW = 18.95, p < 0.005) but stimulated the uptake in (HOB + DEX) cells (KW = 13.52, p < 0.025). E2 decreased the amount of osteocalcin in culture media from both (HOB - DEX) and (HOB + DEX) cells (p < 0.05). PTH alone or E2, alone or in combination with 10(-9)M PTH, had no effect on ALP activity in (HOB - DEX) cells. In contrast, in (HOB + DEX) cells, E2 + PTH but not E2 alone, had biphasic effects on ALP activity, with maximum stimulation observed at 10(-11) and 10(-10)M E2, and a return to basal levels at 10(-9)M E2. E2 decreased basal adenylate cyclase activities in a dose-dependent manner in (HOB + DEX) but not (HOB - DEX) cells (KW = 13.48, p < 0.05). In (HOB + DEX) cells, E2 had biphasic effects on PTH-stimulated adenylate cyclase activity, with significant stimulation observed at 10(-10)M (p < 0.05). While E2 had no significant effect on osteoblastic marker mRNA levels in (HOB - DEX) cells, it decreased osteocalcin and stimulated PTHr mRNA levels in (HOB + DEX) cells. Thus, in our human osteoblastic cell models, estrogen regulated metabolic function largely in the more differentiated cells, by modifying the effects of PTH.
authors.affiliation: Division of Endocrinology and Metabolism, St. Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: L G
authors.initials: LG
authors.lastname: Rao
authors.forename: M S
authors.initials: MS
authors.lastname: Kung Sutherland
authors.forename: S A
authors.initials: SA
authors.lastname: Muzaffar
authors.forename: J N
authors.initials: JN
authors.lastname: Wylie
authors.forename: R J
authors.initials: RJ
authors.lastname: McBroom
authors.forename: T M
authors.initials: TM
authors.lastname: Murray
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000704:Analysis of Variance; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015675:Osteocalcin / Q000096:biosynthesis / Q000235:genetics; D010281:Parathyroid Hormone / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D011863:Radioimmunoassay
chemical_list: D005938:Glucocorticoids; D010281:Parathyroid Hormone; D012333:RNA, Messenger; D015675:Osteocalcin; D004958:Estradiol; D003907:Dexamethasone; D004247:DNA; D000469:Alkaline Phosphatase; D000262:Adenylyl Cyclases