On the mechanism of the increase in prolyl hydroxylase activity in the uterus of the rat given estradiol-17β

Abstract

The activity of prolyl hydroxylase (EC 1.14.11.2: proline. 2-oxoglutarate dioxygenase) and the protein content of the uterus were significantly increased 4hr after the administration of a single dose of estradiol-17β to either the immature rat or the adult ovariectomized rat. In contrast to results in the uterus, prolyl hydroxylase activity was decreased in heart, kidney and lung of the immature rat after estradiol-17β. Prolyl hydroxylase activity reached a maximum in 24–32 hr, and subsequently the enzyme activity decreased toward control values. In both animals, there was a 50 per cent reduction in enzyme activity 8–12hr after reaching maximum activity. The estradiol-17β-induced increase in prolyl hydroxylase activity was blocked by inhibitors of RNA and protein synthesis. In addition, an increase in total enzyme protein was demonstrated using an enzyme immunossay. Although these data provide evidence that de novo synthesis of enzyme protein occurs in the uterus after the administration of estradiol-17β. it does not rule out the possibility that other post-transcriptional effects of estradiol-17β play a role in increasing the activity of this enzyme. Efforts to stimulate uterine prolyl hydroxylase activity with either cAMP or dibutyryl cAMP were unsuccessful.