Fetal rat bone in organ culture: Effect of bone growth and bone atrophy on the comparative losses of45Ca and3H-tetracycline

Publisher Website
Google Scholar
Abstract
Fetal rat bones were cultured in either growth-inducing or resorption-inducing media to study mineral losses during bone growth and atrophy in vitro. Whole radii and ulnae from 19-day-old fetal rats, prelabeled with45Ca and/or3H-tetracycline, were cultured intact or cut, and then digested by collagenase to obtain the calcified portion of the bones. Three-to five-fold more3H-tetracycline than45Ca was lost from the calcified portion when the bones were cultured for 4 days in growth-inducing media. Similar small amounts of45Ca were lost from live and killed bones, but more3H-tetracycline was lost from live bones than from killed bones. More3H-tetracycline was released into the growth medium with a low concentration of calcium (0.5 mM) than when the calcium concentration was high (1.0 mM); no significant difference was seen in the release of45Ca into the medium at different calcium concentrations. Larger amounts of both isotopes were lost when the prelabeled bones were cultured in resorption-inducing media than in growth-inducing media. When parathyroid hormone stimulated bone resorption in a resorption-inducing medium, equal proportions of both isotopes and bone collagen were lost. Greater losses of3H-tetracycline than of45Ca suggest that45Ca was conserved locally during the resorption that accompanies bone growth, but not during resorption that accompanies bone atrophy.