title: An improved model of the distribution and metabolism of progesterone and 20 alpha-dihydroprogesterone in sheep.
abstract: When [3H]progesterone is infused intravenously into ewes, blood 20 alpha-dihydroprogesterone (20 alpha-diHP) becomes labelled and the changes in [3H]20 alpha-diHP activity with time are clearly related to that of [3H]progesterone. Concentrations of 20 alpha-diHP in blood have now been estimated for these experiments. During the infusion, the specific radioactivity of 20 alpha-diHP at steady state was only 53% of the specific radioactivity of progesterone, indicating that 20 alpha-diHP was produced other than by C-20 reduction of secreted progesterone. The change in blood concentration of 20 alpha-diHP during pregnancy in ewes suggests that the placenta is its source. [3H]20 alpha-dihydroprogesterone was infused into pregnant ewes and the specific radioactivity of 20 alpha-diHP measured during and after infusion. Together with information from earlier experiments when [3H]progesterone was infused, there is now sufficient data to estimate, without constraint, the parameters of a four-pool model describing the distribution and metabolism of progesterone and 20 alpha-dyhydro-progesterone in sheep.
mesh_terms: D004092:20-alpha-Dihydroprogesterone / Q000097:blood / Q000378:metabolism; D000818:Animals; D005260:Female; D008954:Models, Biological; D011247:Pregnancy; D011374:Progesterone / Q000097:blood / Q000378:metabolism*; D012756:Sheep / Q000378:metabolism*
chemical_list: D004092:20-alpha-Dihydroprogesterone; D011374:Progesterone