Effects of Hyperadrenalism on Bovine Ovarian Function
Li, Pi-Hsueh Shirley
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Permalink
https://hdl.handle.net/2142/71294
Description
Title
Effects of Hyperadrenalism on Bovine Ovarian Function
Author(s)
Li, Pi-Hsueh Shirley
Issue Date
1982
Department of Study
Veterinary Medical Science
Discipline
Veterinary Medical Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Animal Physiology
Abstract
Effects of hyperadrenalism on bovine ovarian function were studied by using 25 intact heifers treated with ACTH or saline (S) and 33 adrenalectomized (ADRX) heifers treated with ACTH, hydrocortisone succinate (HS), progesterone (P) or S and bovine pituitary cells in culture. All ADRX animals were maintained on 10 mg DOCA and 25 mg cortisone acetate daily. The infusion of 1-24 ACTH (1 mg per 24 hours), HS (100 mg per 24 hours) or S was administered at a rate of 10 ml per hour. The progesterone intravaginal device was used. In experiment 1 (8 intact and 19 ADRX heifers), treatments were from day 2 through next estrus or day 25, whichever occurred first. Blood samples were collected from indwelling catheters at 0800, 1200, and 1600. In intact animals, luteinizing hormone (LH) was > 1 ng/ml from days 2-4 in controls but < 1 ng/ml in ACTH animals, suggesting that continuous infusion of ACTH depresses LH secretion in the early cycle which may represent a stimulus for maximal corpus luteum development and P secretion which occurs after day 4. However, in the ADRX animals, there was no difference in LH concentrations between S and treated groups. In experiment 2 (11 intact and 8 ADRX heifers), treatments (ACTH, 0.5 mg per 24 hours, HS, or S) started on day 16 and continued for 14 days. Blood samples were collected at 4-hour intervals beginning on cycle day 14. Infusion of intact heifers with ACTH and ADRX heifers with HS blocked ovulation. In experiment 3 (6 intact and 6 ADRX heifers), treatments (ACTH, 0.5 mg per 24 hours, HS, 720 mg per 24 hours or S) started on day 2. On days 7, 9, and 11, or days 5, 7, and 9, a single iv dose of GnRH (100 (mu)g) was given to intact or ADRX animals, respectively. Samples for LH assay were collected at 15 minute intervals and indicated that the response of LH to GnRH was significantly reduced or changed by ACTH or HS. The results suggest that the main site of action of adrenal hormones may be at the pituitary. In experiment 4, bovine pituitary cells were dispersed with collagenase and pancreatin and 2 x 10('6) cells in 2 ml medium were distributed to the tissue culture dishes (35 x 10 minimeters). Cells were preincubated with cortisol before GnRH was added. Exposure of pituitary cells to HS at concentrations of 5 ng/ml or higher for periods of 8 hours or longer decreased basal and GnRH-stimulated LH release, but did not change cell LH content. Total protein content of the pituitary cells was not decreased by the HS treatment. These findings suggest that the chronic exposure of bovine pituitary cells to cortisol decreases basal LH release and the sensitivity of bovine pituitary cells to GnRH.
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