Steroidogenic cell populations in follicles of the chicken ovary
Nitta, Hiroaki
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Permalink
https://hdl.handle.net/2142/19514
Description
Title
Steroidogenic cell populations in follicles of the chicken ovary
Author(s)
Nitta, Hiroaki
Issue Date
1992
Doctoral Committee Chair(s)
Bahr, Janice M.
Department of Study
Animal Science
Discipline
Animal Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Anatomy
Biology, Animal Physiology
Biology, Veterinary Science
Language
eng
Abstract
A two cell theory for steroidogenesis in preovulatory follicles of the chicken ovary states that the granulosa layer metabolizes cholesterol to progestins and progestins are, then, metabolized to androgens and estrogens by the theca layer. However, the precise site of steroidogenic cells in the theca layer of preovulatory follicles and in small follicles of the chicken ovary has not been identified. Therefore, objectives of my dissertation were: (1) to identify steroidogenic cells in the theca layer of preovulatory follicles by immunocytochemistry for P450 steroidogenic enzymes and to measure steroid production by isolated theca cells in a short term cell incubation (Experiment 1); (2) to localize cell populations containing P450 steroidogenic enzymes in small follicles by immunocytochemistry (Experiment 2); and (3) to identify the site of 3$\beta$-hydroxysteroid dehydrogenase (3$\beta$-HSD) in small, preovulatory, and postovulatory follicles (Experiment 3). Follicles were obtained from regularly laying chickens 2 hours after oviposition of the first egg of a clutch. P450 steroidogenic enzymes stained in Experiments 1 and 2 were cholesterol side-chain cleavage cytochrome P450, 17$\alpha$-hydroxylase cytochrome P450, and aromatase cytochrome P450 to identify pregnenolone-, androgen-, or estrogen-producing cells, respectively.
Experiment 1. The theca layer of preovulatory follicles contains three steroidogenic cell populations: (1) interstitial cells for progestin and androgen production from cholesterol; (2) fibroblasts as a possible conversion site from progestins to androgens; and (3) aromatase cells for estrogen production from androgens (a multiple cell theory for steroidogenesis in the theca layer of preovulatory follicles).
Experiment 2. In small follicles, the theca layer, but not the granulosa layer, is the site of steroidogenesis. There are two populations of steroid synthesizing cells in the theca layer of small follicles: (1) interstitial cells for progestin and androgen production and (2) aromatase cells for estrogen production (a two cell theory for steroidogenesis in small follicles).
Experiment 3. The localization of 3$\beta$-HSD shifts from the theca layer of small follicles to the granulosa and theca layers of preovulatory follicles and, then, to the granulosa layer of the postovulatory follicle.
In conclusion, the localization and distribution of steroidogenic cells in follicles change during follicular maturation and the interaction between steroidogenic cells is required for complete steroid production in follicles of the chicken ovary.
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