The Effect of Parathyroid Hormone upon Release of Degradative Enzymes from Rat Bone 1

Summary

The effect of 2 units of PTH on 10-day-old rat tibiae was studied. Incubations were carried out at timed periods up to 48 hr. The following parameters were measured: (a) the release of ⁴⁵Ca from prelabeled bone; (b) the release of [³H]proline and [³H]hydroxy-proline from prelabeled collagen; (c) the release of [methyl-¹⁴C]choline from prelabeled phosphatidyl choline. There was an early release of ⁴⁵Ca from bone fragments that paralleled the degradation of phosphatidyl choline. Collagenolytic activity was not demonstrable until later and reached its maximum 24 to 48 hr after the start of incubation. The data indicated that there is an increasc in the breakdown of phospholipids which occurs at the time calcium mobilization is taking place. Degradation of at least a portion of the organic matrix of bone occurs later.