Document Type

Thesis - University Access Only

Award Date

2001

Degree Name

Master of Science (MS)

Department / School

Animal Science

First Advisor

Jeffrey Clapper

Abstract

Estradiol-17~ (E 2) has been shown to increase serum and anterior pituitary (AP) concentrations of-IGF-1 and relative amounts of serum and AP IGFBPs in several species. The objectives of this experiment were to determine 1) if administration of E 2 implants could elevate serum concentrations of E2 in barrows similar to that of boars of comparable age and maturity and subsequently affect the AP IGF system and, 2) if administration of E2 in barrows increases hypophyseal concentrations ofIGF-1, serum concentrations ofE2 and IGF-1, relative amounts of serum and AP IGFBPs, and concentrations of AP LH and GH compared to boars and non-implanted barrows. In the first experiment twenty crossbred barrows (150 ± 6 d, 103 ± 8 kg) were administered varying doses of E 2 (0, 2, 3, or 4 E 2 implants) over a 35 d period. Blood samples were collected by jugular venipuncture weekly, beginning on d 0. Estradiol implants (25.7 mg E2), were placed subcutaneously at the base of each ear on d 0. Pigs were penned individually and allowed ad libitum access to feed and water. Pigs were killed on d 35 when a blood sample and AP were collected. Serum concentrations of IGF-I, E2 and AP concentrations of LH were determined by RIA. Relative amounts of serum and AP IGFBPs were determined by Western ligand blot analysis. Serum concentrations of E2 were increased (P< .05) in pigs receiving 2, 3, and 4 E2 implants vs O E2 implants, but no difference (P>.05) was detected in serum concentrations of E2 among 2, 3, and 4. Orthogonal contrasts identified that 3 or 4 E2 implants were necessary to increase serum concentrations of E2 to that similar to boars. Serum and AP concentrations ofIGF-I were increased (P< .05) in 2, 3, and 4 pigs compared to non-implanted pigs. Western ligand blot analysis identified 41 and 46 kDa forms of IGFBP-3, 34 kDa IGFBP-2, and 24 and 28 kDa forms of IGFBP-4 in the serum, and 29 kDa IGFBP-5 and 33 kDa IGFBP-2 in the AP. Administration ofE2 tended to increase (P=.09) relative amounts of serum IGFBP-3 ( 41 kDa) vs non-implanted controls. Relative amounts of IGFBP-2 and IGFBP-5 in the AP were increased (P< .05) in response to administration of E2. Anterior pituitary concentrations of LH tended to increase (P=.09) in E2 treated pigs vs non-implanted pigs. Administration ofE2 increased serum and AP concentrations of IGF-1, relative amounts of serum and AP IGFBPs, and AP LH. These findings suggest that E2 may influence AP function in the pig through changes in serum and AP concentratio~s of IGF-I and relative amounts of serum and AP IGFBPs. In the second experiment three groups of pigs were used: boars (n=l l; B), E2 implanted barrows (n=9; E), and non-implanted barrows (n=l2; C). On d 1, a blood sample was taken by jugular venipuncture from all pigs, and every 14 d thereafter. E pigs received four implants (25. 7 mg E2 each), two placed subcutaneously at the base of each ear on d 1. Pigs were penned individually and allowed ad libitum access to feed and water. Pigs were killed on d 90, when a blood sample and APs were collected. Mean serum concentrations of E2 were greater (p< .05) in E vs B pigs. Mean serum concentrations of IGF-I (ng/ml) were greater (p< .05) in B (238.7 ± 6.8) compared to E (170.2 ± 8.9) and C (150.4 ± 6.7) pigs and tended to be greater (p=.08) in E vs C pigs. Mean AP concentrations of IGF-I (ng/mg) were greater (p< .05) in E (773.6 ± 57.0) pigs than B (251.9 ± 51.6) and C (185.6 ± 49.4) pigs. Ligand blot analysis identified 46 and 41 kDa forms of IGFBP-3, 34 kDa IGFBP-2, and 28 and 24 kDa forms of IGFBP-4 in the serum, and 33 kDa IGFBP-2 and 29 kDa IGFBP-5 in the AP. Boars tended to have greater (p=.09) relative amounts of serum IGFBP-3 (41 kDa) vs E and C pigs. Relative amounts of serum IGFBP-2 were greater (p< .05) in E pigs vs B pigs. In the AP, relative amounts of IGFBP-2 and -5 were greater (p< .05) in B pigs compared to E and C pigs. Anterior pituitary concentrations of LH did not differ (p>.05) among treatments. Administration of E2 increased AP concentrations of IGF-1 and tended to increase serum concentrations ofIGF-1 in barrows. Other gonadal factors present in boars may additionally affect the serum and AP IGF system.

Library of Congress Subject Headings

Swine -- Growth
Somatomedin
Estradiol

Publisher

South Dakota State University

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Rights Statement

In Copyright