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|Title:||Regulation of Estrogen Biosynthesis in the Domestic Hen|
|Department / Program:||Animal Science|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Agriculture, Animal Culture and Nutrition|
|Abstract:||The focus of this dissertation was a definition of the mechanism(s) which cause(s) suppression of estradiol (E(,2)) biosynthesis during follicular maturation in the domestic hen. Theca and granulosa layers from the largest (F(,1)), second largest (F(,2)), and third largest (F(,3)) follicles were collected 24, 18, 12, 6 and 2 h before ovulation and isolated cells prepared. Five experiments were done: (1) characterization of optimal conditions for E(,2) secretion by theca cells; (2) measurement of E(,2) secretion by F(,2) and F(,3) theca cells; (3) measurement of androgen production by F(,1), F(,2), and F(,3) granulosa and theca cells; (4) measurement of estrogen production by F(,1), F(,2), and F(,3) granulosa and theca cells; and (5) evaluation of the effect of exogenous progesterone (P(,4)), testosterone (T) and E(,2) secretion by F(,3) theca cells.
Optimal conditions identified were: (a) 1 x 10('6) dispersed theca cells/ml; (b) 1 x 10('-6) M T as substrate; (c) a 3 h incubation period of 40(DEGREES)C; and (d) addition of 0.1% gelatin to Medium 199. During the ovulatory cycle, the ability of F(,2) and F(,3) theca cells to secrete E(,2) from T decreases as the follicle matures except 6 h before ovulation. Incorporation of radiolabelled precursors indicates that granulosa and theca cells are able to convert P(,4) to aromatizable androgens, 5(alpha)-reduced androgens, and estrogen with theca cells having the greater ability. In contrast, F(,2) granulosa cells produce more 5(alpha)-reduced androgens than corresponding theca cells. There are few significant changes in the conversion of P(,4) to androgens by the F(,1), F(,2) and F(,3) theca cells over time. Furthermore, there is no preferential conversion of P(,4) to estrone and estriol in contrast to E(,2) by theca cells. Administration of exogenous P(,4) and E(,2), but not T suppressed the production of E(,2) from T.
The following conclusions are made: (1) theca and granulosa cells secrete androgens and estrogens with theca cells having the greater ability; (2) suppression of E(,2) secretion as follicles mature is not due to a lack of aromatizable androgens, an increase in 5(alpha)-reduced androgens, or a preferential production of E(,1) and/or E(,3); and (3) intragonadal P(,4) and E(,2) may suppress E(,2) secretion by theca cells.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1982.
|Date Available in IDEALS:||2014-12-15|