Evidence of Type Ii Estrogen Receptor in Human Osteoblast‐like Cells

Abstract

Osteoblast-like cells isolated from human bone bioptic specimens were characterized and analysed for the presence of type II estrogen receptor (type II EBS). The amount of type II EBS was measured by a whole-cell assay at 4 degrees C for 2.5 h using [(3)H]-estradiol as tracer. Saturation analysis, used to investigate the binding characteristic of type II EBS, resulted in a sigmoid curve. Scatchard analysis showed the binding affinity of the estrogen receptor, yielding a concave plot. The dissociation constant (K(d)), determined from the [(3)H]-estradiol concentration required for half saturation was about 12+/-2 nM (SD). The number of type II EBS, estimated at maximum binding, was 197,000+/-8800 sites per cell. If the regulation of the receptor by flavonoids would be confirmed, the evidence of type II EBS in osteoblast-like cells could suggest a direct action of ipriflavone and others flavonoids on bone density in postmenopausal osteoporosis.

Bioconversion of norethisterone, a progesterone receptor agonist into estrogen receptor agonists in osteoblastic cells

“…These data are significantly different from the large number of ER binding sites documented in hormone-dependent reproductive cells and tissues (Eriksson et al 1978, Miller & Katzenellenbogen 1983, Chávez et al 1985, Markaverich et al 2001. Interestingly, the rat osteoblasts type II E 2 binding sites found in this study have been previously characterized in human osteoblast-like cells and related with bone formation (Toesca et al 2000).…”

Promoting Effect of Kaempferol on the Differentiation and Mineralization of Murine Pre-osteoblastic Cell Line MC3T3-E1

“…20) Ipri‰avone regulates the mechanism of bone formation via endothelin receptors 16) and via estrogen receptors. 22,23) As shown in Fig. 2, ipri‰avone induced the ALP activity of MC3T3-E1 cells from an early stage after exposure, on day 3, and kaempferol induced the same activity from the intermediate stage, on day 6.…”

Expression and localization of estrogen receptor-β in annulus cells of the human intervertebral disc and the mitogenic effect of 17-β-estradiol in vitro

“…Localization was performed on paraffin-embedded disc tissue or on cultured disc cells [7] using rabbit anti-estrogen receptor beta primary antibody (PA1-311, Affinity Bioreagents, #PA1-311) and streptavidin localization. PA1-311 was produced by Affinity Bioreagents by immunizing New Zealand white rabbits with a synthetic peptide corresponding to the N-terminal amino acid residues 55–70 of rat and mouse ER beta conjugated to KLH; this sequence is completely conserved in human ER beta protein.…”