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Failure of estrogens and androgens to inhibit bone resorption in tissue culture
Abstract:
The effects of estrogens, androgens, and glucocorticoids on bone resorption were compared in organ culture. At a concentration of 10(-5) M, corticosterone, testosterone, dihydrotestosterone, dehydroepiandosterone, estradiol, ethinyl estradiol and estrone did not inhibit the release of 45Ca from 19-day fetal rat long bone shafts in control or para-thyroid hormone (PTH)-treated cultures after 2 or 5 days. Cortisol inhibited both control and PTH-stimulated resorption at 10(-5) M and 10(-6) M. 17beta-Estradiol was inhibitory at 3 X 10(4) M. However, it was less effective than the estrogenically inactive epimer 17alpha-estradiol, in 8 day control cultures or in cultures containing low concentrations of PTH. At 10(-5) m, neither 17beta-estradiol nor 17alpha-estradiol inhibited resorption stimulated by prostaglandin E2 or by osteoclast activating factor.
Insights
Glucocorticoids, like cortisol, inhibit bone resorption, while estrogens and androgens show minimal effects in rat bone organ cultures. This suggests specific hormonal pathways influence bone remodeling.
Area of Science:
- Endocrinology
- Bone Biology
- Pharmacology
Background:
- Bone resorption is a critical process regulated by various hormones.
- Estrogens, androgens, and glucocorticoids are known to influence bone metabolism.
- Understanding their specific effects on bone resorption is crucial for bone health research.
Purpose of the Study:
- To compare the effects of estrogens, androgens, and glucocorticoids on bone resorption in an organ culture model.
- To investigate the inhibitory potential of these steroid hormones on calcium release from fetal rat bone.
Main Methods:
- Organ culture of 19-day fetal rat long bone shafts.
- Treatment with various steroid hormones (corticosterone, testosterone, dihydrotestosterone, dehydroepiandrosterone, estradiol, ethinyl estradiol, estrone, cortisol) at different concentrations (10^-5 M, 10^-6 M).
- Measurement of 45Ca release to quantify bone resorption, with and without parathyroid hormone (PTH), prostaglandin E2, or osteoclast activating factor stimulation.
Main Results:
- Cortisol demonstrated significant inhibition of both basal and PTH-stimulated bone resorption at 10^-5 M and 10^-6 M.
- Estrogens (estradiol, ethinyl estradiol, estrone) and androgens (testosterone, dihydrotestosterone, dehydroepiandrosterone) did not inhibit 45Ca release at 10^-5 M.
- 17beta-estradiol showed inhibition at 3 x 10^-4 M, but was less effective than the inactive epimer 17alpha-estradiol.
- Neither 17beta-estradiol nor 17alpha-estradiol inhibited resorption stimulated by prostaglandin E2 or osteoclast activating factor.
Conclusions:
- Glucocorticoids, particularly cortisol, are potent inhibitors of bone resorption in this model.
- Estrogens and androgens have limited or no direct inhibitory effect on bone resorption under the tested conditions.
- The differential effects highlight the specific roles of different steroid hormone classes in regulating bone remodeling.