7β estradiol-BSA had a Specific membrane Effect on modeling of long bone in Vitro.
17b-Estradiol (E2) had a major role during enchondrial bone growth and development. The regulation of chondrocytes by E2 is mediated by both the classical nuclear receptors and the membranous receptors. However the role of the membranouse effect of E2 during bone modeling is not clear. The aim of the present study is to examine the membrane effects of E2 during bone modeling using E2 conjugated to BSA using in vitro organ culture model. We established a system of fetal long bone culture: fetuses of pregnant mice prelabeled 45Ca were removed on day 16 of gestation. radii and ulnae were dissected and cultured in BGJ medium supplemented with 10% fetal calf serum and vitamin C for 48 hours. The bones were cultured for two days in media contain E2-BSA at concentrations ranging between 10-11-10-7 molar. The bones were harvested and the changes in bone length were measured as indication for the new bone formation, calcium and phosporus content were measured as indication for bone calcification, and 45Ca release was measured as indication for bone resorption. The addition of E2-BSA increase significantly the the diaphyseal length and % accreation at concentration of 10-9-10-7 M with a peak at 10-9 M. Similarly an increase in calcium and phosphoruse content of the bone was found after the addition of E2-BSA . The addition of E2-BSA to the bone had no effect on the release of the 45Ca through the culture period. These results indicate that E2-BSA, which had a specific effect on the membranous receptors, had a direct effects on bone formation and calcification with no effect on bone resorption. The effects of E2-BSA was similar to the results found previously by the addition of E2 to bone in vitro. These results may suggest that the specific membrane effect of E2 had a role during enchondrial bone
