The head extractions, brain and pituitary uptake and metabolism of progesterone and 5alpha-dihydroprogesterone in anesthetized, female rabbits.
Three days after ovariectomy adult female rabbits were injected intramuscularly with either 2 mug estradiol/kg b.w., 0.5 mg progesterone/kg b.w., 2 mug estradiol plus 0.5 mg progesterone/kg b.w., or oil vehicle daily for 5 days. On the sixth day the animals were anesthetized and given a continuous infusion of [14C]progesterone and [3H]5alpha-pregnane-3,20-dione (5alpha-DHP) for 4 h via the femoral vein. Head extractions, calculated from the difference in blood concentrations of radioactive steriods between the femoral artery and jugular vein, were in the range of 60-75% for both progesterone and 5alpha-DHP and were unaffected by the hormone treatments. Nine brain areas and the pituitary were analyzed for [14C]progesterone, [3H]5alpha-DHP and [14C]-5alpha-DHP. Generally, the brain and pituitary retention and distribution of [14C]progesterone and [3H]5alpha-DHP and the brain and pituitary metabolism of [14C]progesterone were unaffected by hormone treatments. In the cerebellum, progesterone treatment increased [14C]progesterone retention as compared to oil treatment. All tissues contained 2-7 times more [14C]progesterone than arterial blood concentrations. [3H]5alpha-DHP tissue: arterial blood concentrations ratios were much lower ranging from 0.9 to 1.78. [14C]progesterone and [3H]5alpha-DHP showed similar brain distribution with highest concentrations in the pons, pons reticulum and midbrain reticulum. All tissues converted progesterone to 5alpha-DHP, but only the cerebellum contained more [14C]5alpha-DHP than [14C]progesterone.
D004092:20-alpha-Dihydroprogesterone / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D001933:Brain Stem / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005263:Femoral Artery; D007031:Hypothalamus / Q000378:metabolism; D007601:Jugular Veins; D008636:Mesencephalon / Q000378:metabolism; D010053:Ovary / Q000502:physiology*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011374:Progesterone / Q000097:blood / Q000378:metabolism* / Q000494:pharmacology; D011817:Rabbits; D013788:Thalamus / Q000378:metabolism
D004092:20-alpha-Dihydroprogesterone; D011374:Progesterone; D004958:Estradiol