title: [Dexamethasone up-regulates the expression of glucocorticoid receptor in growth plate and inhibits the longitudinal growth of bone: experiment with rats].
abstract: OBJECTIVE
  To investigate the regulation of the glucocorticoid of pharmacological doses on the expression of glucocorticoid receptor in growth plate and to explore the mechanism of the direct inhibition of the longitudinal growth of bone by dexamethasone.
  
  
  METHODS
  Twenty 3-week-old male weanling SD rats were randomly divided into two groups: dexamethasone group (n = 12), intraperitoneally injected with dexamethasone 200 microg/100 g body weight once a day for 10 days and control group (n = 8), intraperitoneally injected with normal saline of the same volume. Ten days later the rats were killed. The length of the proximal tibia was excised, fixed and decalcified, and then paraffin embedded. Sections of 5 microm thick were cut and processed for histomorphometry The total height of growth plate, height of proliferative zone, and height of hypertrophic zone were determined.
  
  
  RESULTS
  The length of tibia, total height of growth plate, height of proliferative zone, and height of hypertrophic zone of the dexamethasone group were 28.9 mm +/- 1.2 mm, 4.01 microm +/- 0.28 microm, 1.98 microm +/- 0.13 microm, and 1.67 microm +/- 0.18 microm respectively, all significantly lower those of the control group (30.5 mm +/- 1.1 mm, 5.53 microm +/- 0.46 microm, 2.25 microm +/- 0.30 microm, and 2.87 microm +/- 0.19 microm respectively, all P < 0.01). The resting chondrocytes and hypertrophic chondrocytes in the growth plates of the rats in the dexamethasone group all expressed glucocorticoid receptor, whereas the proliferating chondrocytes didn't. The absorbance values of the resting chondrocytes and hypertrophic chondrocytes in the growth plates of the dexamethasone group were 0.238 +/- 0.026 and 0.283 +/- 0.042 respectively, both significantly higher than those of the control group (0.187 +/- 0.027 and 0.211 +/- 0.022 respectively, both P < 0.01).
  
  
  CONCLUSIONS
  The glucocorticoid receptors are essential for the longitudinal growth of bone. The glucocorticoid of pharmacological dose inhibits the longitudinal growth of bone by up-regulating the expression of glucocorticoid receptor.
authors: Children Hospital of Fudan University, Shanghai 200032, China.
authors: Hui-Feng
authors: HF
authors: Zhang
authors: Wei-Ping
authors: WP
authors: Wang
authors: Yi
authors: Y
authors: Yang
authors: Yan-Ling
authors: YL
authors: Zhang
authors: Ya-Lei
authors: YL
authors: Pi
authors: Xiao-Yu
authors: XY
authors: Tian
authors: Xiu-Fang
authors: XF
authors: Jiang
mesh_terms: D000818:Animals; D001846:Bone Development / Q000187:drug effects*; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D006132:Growth Plate / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D007150:Immunohistochemistry; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D011965:Receptors, Glucocorticoid / Q000096:biosynthesis*; D014886:Weaning
chemical_list: D011965:Receptors, Glucocorticoid; D003907:Dexamethasone