These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Ovarian regulation of hypothalamic and pituitary progestin-metabolizing enzyme activities.
    Author: Krause JE, Bertics PJ, Karavolas HJ.
    Journal: Endocrinology; 1981 Jan; 108(1):1-7. PubMed ID: 7193117.
    Abstract:
    Progesterone 5 alpha-reductase activity and 5 alpha-dihydroprogesterone 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR) activities (NADH-linked) were measured in hypothalamic and pituitary tissues from rats during various stages of the estrous cycle and in ovariectomized rats treated with 17 beta-estradiol or vehicle. Enzyme assays were performed using 3H-labeled steroid substrates and reverse isotopic dilution analyses. Pituitary 5 alpha-reductase activity fluctuated over the estrous cycle, with peak levels observed on proestrus, estrus, and metestrus and lowest levels on diestrous 1 and 2 of 5-day cycling rats. Pituitary NADH-linked 3 alpha-HSOR activity also fluctuated over the estrous cycle, paralleling 5 alpha-reductase activity. The pituitary NADPH-linked 3 alpha-HSOR activity and three hypothalamic enzyme activities, the 5 alpha-reductase, NADH-linked, and NADPH-linked 3 alpha-HSOR activities, did not change over the estrous cycle. After ovariectomy (10 days), pituitary 5 alpha-reductase activity was elevated 10- to 12-fold relative to mean levels in intact rats, while the pituitary NADH-linked 3 alpha-HSOR activity was elevated 4- to 5-fold. Treatment for 3 days with estradiol benzoate (10 micrograms/day) significantly reduced both pituitary 5 alpha-reductase and NADH-linked 3 alpha-HSOR activities to about half the levels observed in ovariectomized rats. The pituitary NADPH-linked 3 alpha-HSOR activity was unaffected by ovariectomy. After ovariectomy, a small decrease was observed in the hypothalamic 5 alpha-reductase; no differences were observed in the NADH-linked or NADPH-linked 3 alpha-HSOR activities of the hypothalamus compared to mean levels in cyclic rats. The results suggest a role of the ovary in the regulation of the pituitary and hypothalamic progesterone 5 alpha-reductase and pituitary NADH-linked 5 alpha-dihydroprogesterone 3 alpha-HSOR activities.
    [Abstract] [Full Text] [Related] [New Search]