Masters Theses

Date of Award

5-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Judy Grizzle

Committee Members

Jim Godkin, Michael Smith, Michael Sims

Abstract

White Leghorn hens selected for a high (HA) or low antibody (LA) response to sheep red blood cells (SRBC) were sacrificed at 10, 20, and 30 weeks of egg production in order to measure steroid production by granulosa and theca cells possibly affected by cytokine treatment. Isolated granulosa cells and theca explants from the three largest preovulatory follicles and granulosa cells from 13-20mm and 9-12mm follicles were incubated for 3 hours at 39°C with cytokine enriched conditioned media from HD-11 chicken macrophage cells, or 5 or 250ng/ml human recombinant tumor necrosis factor alpha (hrTNFα). Progesterone production by granulosa cells and androstenedione secretion from theca cells were measured using validated radioimmunoassays. There were no differences (P>.05) in hen-day egg production or follicle size between LA and HA hens during 30 weeks of egg production. However, significant differences (P≤.05) in progesterone production were observed due to genetic line, follicle size, and duration of egg production. Fl, F2, and F3 granulosa cells from HA hens produced more (P≤.05) progesterone (140.8, 107.2, and 49.7ng/ml) as compared to LA hens (109.4, 78.9, and 26.9ng/inl), whereas 13-20mm and 9- 12mm granulosa cells from LA hens produced more (P≤.05) progesterone, 6.63 and 0.32ng/ml, when compared to HA hens, 5.26 and 0.15ng/ml. Treatment of granulosa cells with HDll conditioned media decreased (P≤.05) progesterone production among all follicle sizes in both genetic lines, except the F2 follicle from HA hens which was not affected (P≤.05). Human recombinant TNFα consistently inhibited (P≤.05) progesterone secretion by all follicles among HA and LA hens, but not always at both doses. Generally, 5ng/ml hrTNFα was the maximum inhibitory dose.

Androstenedione production by thecal explants did not differ (P>.05) between genetic lines, except at 10 weeks of egg production. At this time, F1 theca explants from HA hens produced more androstenedione (P≤.05), 27.0ng/ml, as compared to explants from LA hens, 3.79ng/ml. In contrast, F2 and F3 theca cells from LA hens secreted more (P≤.05) androstenedione, 35.2 ng/ml and 82.0ng/ml, than HA hens, 8.0ng/ml and 46.9ng/ml, respectively. Theca cells were not as responsive to cytokine treatment as granulosa cells. Androstenedione secretion by F1 and F2 theca cells from both genetic lines was not affected (P>.05) by HDll conditioned media at any time period, whereas F3 theca cells from LA hens secreted less (P≤.05) androstenedione in response to HDll conditioned media at 10 and 20 weeks of egg production when compared to untreated cells. Treatment of F1 and F3 theca cells from HA and LA hens, with hrTNFα stimulated (P≤.05) androstenedione production at 10 weeks of egg production, but decreased (P≤.05) androstenedione secretion by F2 theca cells at this time period. Similar to studies in mammals, these results suggest a role for cytokine proteins in steroidogenesis in the chicken. In the laying hen, a decrease in steroid production, mainly progesterone, in response to cytokines may upset the steroid balance created by the follicular hierarchy or inhibit ovulation.

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