Bone resorption, in vitro, is often measured as the release of prelabelled45Ca from neonatal mouse calvarial bones, or from fetal rat long bones. In this report we describe a technique to measure the breakdown of bone-matrix, in vitro. We also describe a new way to dissect neonatal mouse calvarial bones, in order to obtain large amounts of bone samples.

Twelve bone fragments were dissected out from each mouse calvaria and were thereafter cultured in CMRL 1066 culture medium in serum-free conditions in 0.5 cm2 multiwell culture dishes. Matrix degradation after treatment with parathyroid hormone was assessed by measuring the amount of carboxyterminal telopeptide of type I collagen (ICTP) by RIA. The data on matrix degradation was compared to the release of prelabelled45Ca from neonatal mouse calvarial bones. We found that the dose-responses for parathyroid hormone-induced release of prelabelled45Ca and ICTP were identical.

In conclusion: RIA-analysis of the ICTP-release is an easy and accurate method to measure degradation of bone-matrix, in vitro. Furthermore, the new dissection technique, described in this report, makes it easy to obtain large amounts of bone samples and thus to perform extensive experiments, e.g. dose-responses for agents that enhance bone resorption.

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