Abstract
The effect of betamethasone-17-valerate on the biosynthesis of collagen was studied in matrix-free chick embryo tendon cells in vitro and the activity of prolyl hydroxylase was assayed in the cells after incubation with the steroid in vitro and after injection of the steroid on to chorioallantoic membrane of embryonated eggs. Tendon cells synthesized collagen at a rapid rate and the synthesis was essentially linear for up to about 7 hr when studied by labelling with [ 14C]proline. The secretion of collagen [ 14C]hydroxyproline was also almost linear for up to 7 hr. Betamethasone-17-valerate decreased the total incorporation of [ 14C]proline and the decrease in the synthesis of [ 14C]hydroxyproline was larger than the decrease in the total incorporation, indicating that the collagen synthesis was affected more than other protein synthesis. Betamethasone-17-valerate had no effect on the activity of prolyl hydroxylase, when the cells were incubated with this steroid in vitro or, when the activity of the purified enzyme was assayed in the presence of this steroid. When the steroid was injected on to chorioallantoic membrane of embryonated eggs, the activity of prolyl hydroxylase decreased markedly in the tendon cells, indicating that in the system studied the amount of prolyl hydroxylase is decreased or that the enzyme is inactivated by this steroid in vivo.
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