Progress 10/01/02 to 09/30/07
Outputs
OUTPUTS: A series of experiments were conducted to determine the effects of steroids and estradiol specifically,on the peripheral and anterior pituitary gland (AP) insulin-like growth factor (IGF) system in the pig. In all experiments serum and AP concentrations of hormones were determined by RIA and relative amounts of serum and AP IGF binding proteins were determined by Western ligand blot analysis. Previous experiments demonstrated that estradiol (E2) had profound effects on the porcine IGF system, however the influences of testosterone could not be discounted. In one experiment twelve crossbred barrows were divided into groups that received estradiol implants (n = 4), testosterone implants (n = 6) or no implants (n = 5) to determine if testosterone alone effects the IGF system. Blood samples were obtained on d 1 before implantation, then on d 14, 28, 42, 56, and 63. Another experiment was conducted to determine if decreases in serum concentrations of estradiol would cause
concomitant decreases in components of the peripheral and AP IGF system in pigs. Twelve crossbred boars were equally divided into three treatment groups (n = 4/group) and administered the aromatase inhibitor, anastrozole at 0, 1, or 10 mg/d to determine which dose was most effective in decreasing serum concentrations of E2. Blood samples were collected every 7 d for 35 d then pigs were killed on d 36 and AP collected. Following this, another experiment was conducted to determine if the effective dose of anastrozole decreased serum and AP concentrations of components of the IGF system in boars compared to untreated boars and barrows. Blood samples were collected every 14 d from all pigs for 84 d then pigs were killed and AP collected. Because estradiol naturally fluctuates throughout the estrous cycle in the pig an experiment was conducted to determine if serum and AP concentrations of components of the IGF system fluctuate throughout the estrous cycle. Forty gilts of similar age and
weight having regular estrous cycles were fed 15 mg altrenogest for 15 d to synchronize estrus Blood samples were obtained from gilts on d 1, 4, 7, 10, 13, 16, 19 and 22 of the estrous cycle. On d 7, 13, 19, and 22 of the estrous cycle 10 pigs were killed and AP were collected to determine concentrations of components of the IGF system. These days correspond to times when estradiol is naturally increasing and decreasing. Because isoflavones posses estrogenic activity and may be capable of modulating the IGF system in the pig an experiment was conducted to determine if administration of the isoflavone genistein to pigs would modulate components of the peripheral and AP IGF system. Twenty barrows of equal age and weight were divided into one of four groups (n =5/group) controls (C), estradiol (E), 200 mg genistein and 400 mg genistein. Pigs were injected with the corresponding treatments intramuscularly for 15 d. Blood was collected on days 0, 3, 6, 9, and 12. Blood and AP were
collected at slaughter on d 15. Results have been disseminated to the scientific community through publication in the Journal of Animal Science, Journal of Endocrinology, and Biology of Reproduction.
PARTICIPANTS: Jeffrey Clapper, PI, South Dakota State University Erin Stansbury, Undergraduate Student, South Dakota State University Chaundra Hilleson Gayne, Graduate Student, South Dakota State University Amanda Knoor, Graduate Student, South Dakota State University Anna Taylor, Graduate Student, South Dakota State University
TARGET AUDIENCES: Target audience was the scientific community, specifically physiologists
Impacts
Mean serum concentrations of E2 and testosterone increased (P<.05) in the E2 implanted and testosterone implanted pigs, respectively from d 14 through d 63 compared to controls. Mean serum concentrations of IGF-I were greater (P<.05) in E2 pigs than in testosterone or control pigs. Mean relative amounts of IGB binding protein (IGFBP)-3 were decreased (P<.05) in testosterone pigs compared to E2 or control pigs. These results indicate that E2 may increase circulating IGF-I and testosterone may alter relative amounts of IGFBP-3. The aromatase inhibitor, anastrozole, was capable of decreasing (P<.05) serum concentrations of estradiol at the 10 mg dose after 14 d of administration and continued to decrease E2 for 35 d. Relative amounts of serum IGFBP-3 were greater (P<.01) in 10 mg pigs vs those receiving 1 mg anastrozole. These results indicate 10 mg of anastrozole/d may be useful in decreasing serum concentrations of E2 in pigs. In the next experiment when pigs were
treated with 10 mg anastrozole/d for a longer period of time mean serum concentrations of E2 decreased (P<.05) vs controls by d 15 and remained decreased throughout the remainder of the study. On d 0, 15, 43, mean serum concentrations of IGF-I were greater (P<.05) in anastrozole boars than in untreated boars, and each was greater (P<.05) than barrows throughout. Mean relative amounts of the 24 kDa form of IGFBP-4 in serum were greater (P<.01) in anastrozole boars than in untreated boars and barrows, but untreated boars and barrows did not differ (P>.05). Mean relative amounts of AP IGFBP-2 and IGFBP-5 were less (P<.01) in anastrozole boars than untreated boars, but each was greater (P<.01) than barrows. These data further support a role for E2 in regulating components of the AP IGF system in pigs. Components of the IGF system have been found to fluctuate throughout the estrous cycle with circulating concentrations of E2. Mean serum concentrations of IGF-I decreased (P<.02) from d 1
through d 10, then increased (P<.02) on d 13 through 16, then decreased (P<.02) from d 19 through 22. Mean AP concentrations of IGF-I were greater (P<.03) on d 19 compared to all other days, while no difference was detected (P>.05) in mean anterior pituitary concentrations of IGF-I on d 7, 13, and 22. Mean relative amounts of AP IGFBP-2 and -5 were each greater (P<.02) in gilts on d 19 compared to all other days while no difference was detected in mean relative amounts of AP IGFBP-2 and -5 among pigs on d 7, 13, and 22 of the estrous cycle. These data provide evidence that concentrations of components of the serum and AP IGF system fluctuate during the estrous cycle in pigs. The isoflavone, genistein, has also been found to modulate the porcine IGF system. AP concentrations of IGF-I were greatest in E pigs (P<.05), while the 400 pigs had greater (P<.05) AP concentrations than C pigs. No difference was detected (P>.05) in AP concentrations of IGF-I between the 200 pigs and the C pigs.
These preliminary data provide evidence that genistein affects the AP IGF system in the pig.
Publications
- Taylor, A.R., Clapper, J.A. 2007. Serum and anterior pituitary (AP) concentrations of IGF-I and relative amounts of AP IGF binding proteins throughout the estrous cycle in gilts. J. Anim. Sci. 85 (Suppl. 1):270.
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Progress 01/01/06 to 12/31/06
Outputs
Administration of insulin-like growth factor -I (IGF-I) to porcine anterior pituitary cells in vitro has been demonstrated to increase the secretion of luteinizing hormone (LH) in response to gonadotropin releasing hormone. It has been established that components of the circulating and anterior pituitary concentrations of the porcine IGF system vary in response to administration of estradiol (E). However, whether serum and anterior pituitary concentrations of the IGF system vary throughout the estrous cycle, with changing levels of E has not been determined. To further examine this relationship the following experiment was performed. Forty gilts of similar age and weight (180 d; 120 kg) were injected with 400 IU pregnant mare serum and 200 IU human chorionic gonadotropin to induce the gilts into puberty. Fifteen days later all gilts were fed 15 mg altrenogest for 15 d to synchronize estrus. Gilts were checked twice daily for expression of estrus by exposure to a
mature boar beginning 3 d after the end of altrenogest treatment and continuing for 7 d. The first day each gilt exhibited estrus in response to exposure to the boar was designated as d 1 of the estrous cycle. Blood samples were obtained by jugular venipuncture on d 1, 4, 7, 10, 13, 16, 19, and 22 of the estrous cycle. On d 7, 13, 19, and 22 of the estrous cycle 10 pigs were killed and anterior pituitary glands (AP) were collected. Serum concentrations of IGF-I and AP concentrations of IGF-I were determined by RIA. Relative amounts of AP IGF-binding proteins (IGFBP) were determined by Western ligand blot analysis. Serum concentrations of IGF-I fluctuated throughout the estrous cycle. Mean serum concentrations of IGF-I decreased (P<.02) from d 1 through d 10, then increased (P<.02) on d 13 through 16, then decreased (P<.02) from d 19 through 22. Mean AP concentrations of IGF-I were greater (P<.03) on d 19 compared to all other days, while no difference was detected (P>.05) in mean
anterior pituitary concentrations of IGF-I on d 7, 13, and 22. Western ligand blot analysis identified 33 kDa IGFBP-2 and 29 kDa IGFBP-5 in the AP. Mean relative amounts of AP IGFBP-2 and -5 were each greater (P<.02) in gilts on d 19 compared to all other days while no difference was detected in mean relative amounts of AP IGFBP-2 and -5 among pigs on d 7, 13, and 22 of the estrous cycle. These data provide evidence that concentrations of components of the serum and AP IGF system fluctuate during the estrous cycle in pigs. Anterior pituitary gland function in the pig may be influenced by the IGF system in response to the changing steroidal milieu that occurs during the estrous cycle.
Impacts
Estrogens have been shown to affect anterior pituitary gland function in the pig. Additionally, estrogens have been demonstrated to affect the IGF system. Results from the current study show that components of the anterior pituitary gland IGF system fluctuate throughout the estrous cycle of the pig, which may directly influence anterior pituitary gland function and subsequent reproduction.
Publications
- Clapper, J.A., Stansbury, E.M. 2006. Effects of estradiol and testosterone on the peripheral and anterior pituitary IGF system in barrows. J. Anim. Sci. 84 (Suppl. 1):136.
- Wertz-Lutz, A.E., Knight,T.J., Pritchard, R.H., Daniel, J.A., Clapper, J.A., Smart, A.J., Trenkle, A., Beitz, D.C. 2006. Circulating ghrelin concentrations fluctuate relative to nutritional status and influence feeding behavior in cattle. J. Anim. Sci. 84:3285-3300.
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Progress 01/01/05 to 12/31/05
Outputs
It is well established that boars grow faster and more efficiently than barrows and gilts and have greater circulating concentrations of insulin-like growth factor-I (IGF-I), estradiol, and tesotsterone. Estradiol (E) has been demonstrated to alter components of the peripheral IGF system in pigs, however, testosterone (T) may also play a role. Exact mechanisms by which each steroid may influence the IGF system remain to be determined. To further delineate the effects of E and T on the IGF system in pigs the following experiment was conducted. Fifteen crossbred barrows of similar age and weight (100 d, 53.4 kg) were stratified by litter to one of three treatment groups. Treatments were barrows receiving no E or T (C; n = 5), those receiving E (E; n = 4), and those receiving T (T; n = 6). Two E implants (Compudose) were placed subcutaneously in one ear of E pigs while T pigs received two silastic tubing implants filled with crystalline T (5 cm x 0.465 cm) placed
subcutaneously in the base of each ear. Blood samples were obtained on d 1 before implantation, then on d 14, 28, 42, 56, and 63. Mean serum concentrations of E were not different (P>.05) among groups on d 1 but by d 14 through 63, mean serum concentrations of E were greater (P<.05) in E pigs than in T or C pigs. Mean serum concentrations of T were increased (P<.05) in T pigs from d 14 through 63 compared to d 1. Mean serum concentrations of IGF-I were greater (P<.05) in E pigs than in C or T pigs. Western ligand blot analysis identified 46- and 41- kDa forms of IGFBP-3 and a 34 kDa IGFBP-2 in serum. Mean relative amounts of 46- and 41-kDa IGFBP-3 in serum were decreased (P<.05) in T pigs compared to E and C pigs. No difference (P>.05) was detected in mean relative amounts of serum IGFBP-2 among treatments. These preliminary data provide evidence that while E may increase circulating IGF-I, T may alter relative amounts of IGFBP-3 to effectively increase the bioavailabilty of IGF-I in
the pig.
Impacts
Steroids such as estrogens and androgens are known to affect growth through the insulin-like growth factor (IGF) system. Exact mechanisms by which each work in swine is unknown. These results demonstrate that estrogens and androgens may affect the insulin like growth factor system differently in order to increase the availability of IGF and affect animal growth.
Publications
- Hilleson-Gayne, C.K., Clapper, J.A. 2005. Effects of decreased estradiol-17b on the serum and anterior pituitary insulin-like growth factor-I (IGF-I) system in pigs. J. Endocrinol. 187:369-378.
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Progress 01/01/04 to 12/31/04
Outputs
Administration of estradiol-17b (E2) to barrows has been shown to increase anterior pituitary (AP) concentrations of IGF-I, but boars still had greater relative amounts of AP IGF-binding protein-2 (IGFBP) and IGFBP-5. To determine the effect of decreased levels of E2 on the serum and AP IGF system, 24 crossbred boars and 12 barrows of similar age (110 d) and weight (44 kg) were stratified by litter to one of three treatment groups (n=12) on day 0. Treatment groups consisted of boars administered 10 mg of an aromatase inhibitor, anastrozole, (A), boars administered 0 mg daily (B), and barrows (BAR). Pigs were penned separately and received ad libitum access to water and fed a diet that contained 2.5 fold the energy requirements for maintenance. Pigs were bled and weighed on d 0 and every two weeks thereafter, then killed on d 84 when a blood sample and AP were collected. Serum concentrations of E2, testosterone (T), IGF-I, and AP concentrations of IGF-I and LH were
determined by RIA. Relative amounts of serum and AP IGFBP were determined by Western ligand blot analysis. Mean serum concentrations of E2 did not differ (P>.05) between A and B pigs on d 0; however, on d 15 through d 84 mean serum concentrations of E2 were greater (P<.05) in B than A pigs. Mean serum concentrations of T did not differ (P>.05) between B and A pigs until d 84 when mean serum concentrations of T were greater (P<.01) in B than A pigs. On d 0, 15, 43, mean serum concentrations of IGF-I were greater (P<.05) in A than B pigs, and each was greater (P<.05) than BAR throughout. Mean AP concentrations of LH and IGF-I did not differ (P>.05) in B and A pigs, but each was greater (P<.01) than BAR. Mean relative amounts of IGFBP-3 in serum did not differ (P>.05) in B and A pigs, but each was greater (P<.01) than BAR. Mean relative amounts of the 24 kDa form of IGFBP-4 in serum were greater (P<.01) in A than B and BAR pigs, but B pigs and BAR did not differ (P>.05). Mean relative
amounts of AP IGFBP-2 and IGFBP-5 were less (P<.01) in A than B pigs, but each was greater (P<.01) than BAR. These data further support a role for E2 in regulating components of the AP IGF system in pigs.
Impacts
In order to study the influence of steroids and/or other gonadal factors in swine it is necessary to reduce steroid levels while leaving the animals gonadally intact. These results demonstrate that estradiol plays a key role in regulating relative amounts of IGFBP in the anterior pituitary gland in the pig.
Publications
- Hilleson-Gayne, C., Clapper, J.A. 2004. Effect of decreased estradiol-17b on the IGF system in pigs. J. Anim. Sci. 82 (Suppl. 2):241.
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Progress 01/01/03 to 12/31/03
Outputs
Twelve crossbred boars of similar age (292.5 d) and weight (159 kg) were stratified by litter to one of three treatment groups (n = 4) on d 1. Treatment groups were 0, 1, 10 mg anastrozole (A) administered daily for 35 d. boars were penned separately and received ad libitum access to food and water. Blood samples were collected on d 1, 7, 14, 28, and 35 by jugular venipuncture. Pigs were killed on d 36 when anterior pituitary glands (AP) were collected. Serum concentrations of estradiol (E2), testosterone (T), IGF-I and AP concentrations of IGF-I and LH were determined by RIA. Relative amounts of serum IGF binding proteins (IGFBP) were determined by Western ligand blot analysis. Serum concentrations of E2 and T were each similar (P>.05) among groups on d 1. By d 14 serum concentrations of E2 (pg/ml) were decreased (P<.01) in pigs receiving 1 and 10 mg A compared to the 0 mg group (0 mg, 331.9; 1 mg, 107.9; 10 mg, 78.5). Serum concentrations of E2 in 10 mg pigs
continued to be less (P<.01) than 0 mg pigs throughout the remainder of the experiment. Serum concentrations of E2 were similar (P>.05) in 1 and 10 mg pigs until d 35 when 1 mg pigs had greater (P<.05) serum concentrations of E2 than 10 mg pigs. Serum concentrations of T were similar (P>.05) among groups throughout the experiment. Western ligand blot analysis identified 41 and 46 kDa forms of IGFBP-3, IGFBP-2, and 24 and 28 kDa forms of IGFBP-4 in the serum. Relative amounts of serum IGFBP-3 (41 kDa) were greater (P<.01) in 10 mg pigs vs 1 mg pigs. No difference was detected in relative amounts of any other serum IGFBP. These preliminary data indicate that anastorzole may be useful in decreasing serum concentrations of estradiol in pigs. Both 1 and 10 mg doses decreased serum concentrations of estradiol, however the 10 mg dose had more lasting effect.
Impacts
In order to study the influence of steroids and/or other gonadal factors in swine it is necessary to reduce steroid levels while leaving the animals gonadally intact. These results demonstrate that administration of an aromatase inhibitor is an effective way of reducing serum concentrations of estradiol in gonadally intact boars.
Publications
- Hilleson-Gayne, C., Clapper, J.A. 2003. Use of an aromatase inhibitor to decrease serum concentrations of estradiol in boars. Biol. Reprod. 68(Suppl. 1):631.
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