[Dexamethasone up-regulates the expression of glucocorticoid receptor in growth plate and inhibits the longitudinal growth of bone: experiment with rats].
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.
Zhang
Hui-Feng
HF
Children Hospital of Fudan University, Shanghai 200032, China.
Wang
Wei-Ping
WP
Yang
Yi
Y
Zhang
Yan-Ling
YL
Pi
Ya-Lei
YL
Tian
Xiao-Yu
XY
Jiang
Xiu-Fang
XF
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
D011965:Receptors, Glucocorticoid; D003907:Dexamethasone