In vitro studies on collagen metabolism in metaphyseal rat bone. B. The early effects of oestradiol-17 beta.

In vitro collagen metabolism in metaphyseal bone has been studied during the first few hours and days after the start of in vivo treatment of castrated female rats with various doses of oestradiol-17 beta. Already during the first 2 h after the start of treatment with oestradiol-17 beta 2 mug/day and within the first 24 h in the rats receiving 20 mug/day, a reduction of the collagen incorporation rate was demonstreated. The incorporation rates remained at approximately the same reduced level during the following 3 weeks. In rats receiving oestradiol-17 beta 1 mug/day no such reduced incorporation rate could be demonstrated during the first 36 h after the start of treatment. The bone collagen resorption rate was significantly elevated during the first 3 days of treatment in the animals receiving oestradiol-17 beta both 1 and 20 mug/day. After this time the resorption rates gradually fell to levels significantly below controls at 3 weeks after start of treatment.