| Autor: |
Looper, M.L., Vizcarra, J.A., Wettemann, R.P., Malayer, J.R., Braden, T.D., Geisert, R.D., Morgan, G.L. |
| Předmět: |
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| Zdroj: |
Journal of Animal Science; Jan2003, Vol. 81 Issue 1, p269, 10p, 3 Charts, 3 Graphs |
| Abstrakt: |
Nutritionally induced anovulatory cows (n = 28) were used to determine the effect of steroids on regulation of synthesis and secretion of gonadotropins. Anovulatory cows were ovariectomized and received intravaginal inserts containing estradiol (E[sub 2]), progesterone (P[sub 4]), E[sub 2] and P[sub 4] (E[sub 2]P[sub 4]), or a shamintravaginal insert (C) for 7 d. Concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were quantified in serum and E[sub 2] and P[sub 4] were quantified in plasma. Cows were exsanguinated within I to 2 h after removal of intravaginal inserts and pituitary glands were collected and stored at -80°C until messenger ribonucleic acid (mRNA) for gonadotropin-releasing hormone receptor (GnRH-R) and gonadotropin subunits, pituitary content of GnRH-R, and LH and FSH were quantified. Pituitary glands from five proestrous cows were harvested to compare gonadotropin characteristics between ovariectomized, anovulatory cows and intact cows. Plasma concentrations of E[sub 2] were greater (P < 0.05) in E[sub 2]-treated cows than in sham-treated cows. Concentrations of P[sub 4] were greater (P < 0.05) in cows treated with P[sub 4] than in shamtreated cows. Mean serum concentrations of LH and FSH were not significantly influenced by steroid treatments. However, frequency of LH pulses of ovariectomized, nutritionally induced anovulatory cows was increased (P < 0.05) by treatment with E[sub 2] and amplitude of LH pulses was greater (P < 0.05) in cows treated with E[sub 2] or P[sub 4] than in cows treated with E[sub 2]P[sub 4] or sham-treated. Quantity of mRNA for LHβ in the pituitary gland was greater when cows were treated with P[sub 4]. Concegland were not affected by steroid treatments; however, pituitary concentrations of FSH were less (P < 0.1) in E[sub 2] cows than in sham-treated cows. The number of GnRH-R was increased (P < 0.05) in cows treated with E[sub 2], but P[sub 4] treatment did not influence the... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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