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Effect of estrogen administration on endogenous and luteinizing hormone-releasing-hormone-induced luteinizing hormone secretion and follicular development in the lactating sow



Effect of estrogen administration on endogenous and luteinizing hormone-releasing-hormone-induced luteinizing hormone secretion and follicular development in the lactating sow



Biology of Reproduction 44(6): 975-982



The objectives of this study were to investigate whether estradiol treatment during lactation modifies 1) the patterns of endogenous LH, FSH, and prolactin (PRL) release; 2) the sensitivity of the pituitary to exogenous injections of LHRH; and 3) the responsiveness of the ovarian follicles to gonadotropin. Plasma LH, FSH, and PRL were determined in samples taken repeatedly from 18 sows on Days 24-27 of lactation. Ovaries were then recovered, and follicular development was assessed by measuring the follicular diameter (FFD) and follicular fluid estradiol-17 beta concentration (FFE) of the ten largest follicles dissected from each ovary. Sows were randomly allocated to one of four treatments: 1) Group C (4 sows) received no treatment; 2) Group LHRH (5 sows) received 800 ng of LHRH every 2 h throughout the sampling period; 3) Group E2 (4 sows) received subcutaneous implants containing estradiol-17 beta 24 h after start of sampling; 4) Group LHRH + E2 (5 sows) were administered a combination of LHRH and estradiol-17 beta implants. Between-animal variability for plasma LH, FSH, and PRL was considerable. LH concentration and LH pulse frequency increased (p < 0.05) after LHRH treatment in the LHRH and LHRH + E2 groups; however, an acute inhibition of LH secretion was observed in the latter group immediately after estradiol implant application. In the absence of LHRH treatment, estradiol caused chronic inhibition of LH secretion. Follicular development was greater in the LHRH and LHRH + E2 groups compared to the C and E2 groups (p < 0.05 for both FFD and FFE). There were no differences in FSH and PRL concentrations between groups, nor between any periods of sampling within groups. These data demonstrate that during late lactation in the sow, a chronic elevation in plasma estradiol levels 1) does not modify FSH and PRL secretion, 2) inhibits LH secretion by acute and chronic effects at the pituitary and hypothalamic levels, and 3) does not increase the sensitivity of the ovary to gonadotropins.

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Accession: 002082077

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PMID: 1908331


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Effect of estrogen administration on endogenous and luteinizing hormone- releasing-hormone-induced luteinizing hormone secretion and follicular development in the lactating sow. Biology of Reproduction 44(6): 975-982, 1991

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