To what extent is estrogen a qualitatively distinct trophic stimulus in the pituitary?

LA Nolan, A Levy

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

Abstract

Physiological levels of circulating corticosterone and testosterone tonically inhibit mitotic activity in the pituitary. The wave of increased mitosis that results from withdrawal of either or both of these lasts for less than a week despite their continuing absence. In contrast, estrogen is a very powerful pituitary mitogen that at high dose is believed to exert a continuous trophic stimulus. To investigate this, we have carried out a careful analysis of the effects of 7 and 28 days estrogen treatment on anterior pituitary mitotic activity in ovariectomized 10 week-old Wistar rats using both bromodeoxyuridine (BrdU) and timed colchicine-induced mitotic arrest methodology. An estrogen dose-dependent increase in mitotic index was seen 7 days after the start of treatment as expected, representing an acceleration in gross mitotic rate from 1.7%/day in the absence of any estrogen replacement to 3.7%/day following the higher dose of estrogen treatment. Despite continued exposure to high dose estrogen and persistence of the increase in pituitary wet weight, the increase in mitotic index was unexpectedly not sustained. After 28 days of high dose estrogen treatment, anterior pituitary mitotic index and BrdU-labelling index were not significantly different from baseline. These data suggest that in keeping with other trophic stimuli to the pituitary, the mitotic response to longer-term high dose estrogen exposure is transient and is not the driver of persistent pituitary growth, at least in female Wistar rats.
Translated title of the contributionTo what extent is estrogen a qualitatively distinct trophic stimulus in the pituitary?
Original languageEnglish
Title of host publicationBritish Society for Neuroendocrinology meeting, Bristol
Number of pages1
Publication statusPublished - 2008

Bibliographical note

Name and Venue of Event: british Society for Neuroendocrinology meeting, Bristol
Conference Proceedings/Title of Journal: Journal of Neuroendocrinology
Conference Organiser: British Society for Neuroendocrinology

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