Progress 10/01/00 to 09/30/03
Outputs
We completed every aim of our original proposal. The objectives from our proposal and progress toward comleting them are as follows. 1) Evaluate potential mechanisms for corticosterone (CORT)-induced growth hormone (GH) cell differentiation. We determined that the regulation of GH induction in embryonic pituitary cells involves the induction of an unknown intermediate protein. Three approaches (ribonuclease protection assay, in situ hybridization of cultured cells, and whole mount in situ hybridization following injection of CORT in ovo) indicate that CORT induces GH gene expression in caudal anterior pituitary cells that formerly did not contain GH mRNA. Pit-1 mRNA levels were assessed after CORT treatment, but no difference in Pit-1 signal was seen between CORT and untreated samples. Furthermore, CORT treatment did not increase the abundance of Pit-1 containing cells. 2) Determine somatostatin (SST) effects on GH secretion and somatotroph differentiation. We defined
that the type 2 somatostatin receptor regulates GH secretion in chickens. SST receptor subtype selective agonists were tested for their ability to reduce GH secretion. The agonist for the type 2 receptor was the only one that was effective. We cloned a partial cDNA for the type 2 receptor and showed that was expressed in the anterior pituitary. 3) Define involvement of the hypothalamo-pituitary-adrenal (HPA) and hypothalamo- pituitary-thyroid (HPT) axes in regulating GH cell differentiation. We found that treatment with the thyroid hormone synthesis inhibitor methimazole partially suppressed normal somatotroph differentiation. We determined that administration of ACTH in vivo increased the abundance of GH cells during embryonic development.
Impacts
We have demonstrated that production of the hormone that controls growth in broiler chickens is regulated during embryonic development by other hormones produced by the adrenal and thyroid glands. Future attempts at improving broiler production may be concentrated on these hormones.
Publications
- Porter TE, Dean CE, Piper MM, Medvedev KL, Ghavam S, Sandor S (2001) Growth hormone gene expression and secretagogue responses in somatotrophs induced to differentiate with glucocorticoids. J Endocrinol 169:499-509
- Porter TE, Dean KJ (2001) Regulation of chicken embryonic growth hormone secretion by corticosterone and 3,5,3'-triiodothyronine: Evidence for a negative synergistic response. Endocrine 14:363-368
- Bossis I, Porter TE (2001) Identification of the somatostatin receptor subtypes involved in regulation of growth hormone secretion in chickens. Mol Cell Endocrinol 182:203-213
- Bossis I, Porter TE (2003) Evaluation of glucocorticoid-induced growth hormone gene expression in embryonic pituitary cells using a novel in situ mRNA quantitation method. Mol Cell Endocrinol 201:13-23
- Liu L, Dean CE, Porter TE (2003) Thyroid Hormones Interact with Glucocorticoids to Affect Somatotroph Abundance in Chicken Embryonic Pituitary Cells In Vitro. Endocrinology 144:3836-3841
- Liu L, Porter TE (2004) Endogenous thyroid hormones modulate pituitary somatotroph differentiation during chicken embryonic development. J Endocrinol 180:45-53
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Progress 01/01/02 to 12/31/02
Outputs
The specific aims of our proposal and our progress toward comleting them are as follows. 1) Evaluate potential mechanisms for corticosterone-induced GH cell differentiation. We know that GH induction in embryonic pituitary cells involves an unknown intermediate protein. We have identified three candidates for this protein, DEXRAS1, GILZ and SGK. 2) Determine somatostatin (SST) effects on GH secretion and somatotroph differentiation. We reported previously that the type 2 somatostatin receptor regulates GH secretion in chickens. However, we have determined that SST does not affect corticosterone induction of somatotrophs. 3) Define involvement of the hypothalamo-pituitary-adrenal (HPA) and hypothalamo- pituitary-thyroid (HPT) axes in regulating GH cell differentiation. Previously, we found that inhibition of thyroid hormone synthesis suppressed normal somatotroph differentiation. and that injection of adrenocorticotropin (ACTH) induced GH cells during embryonic
development. We have determined that the actions of thyroxine require conversion to triiodothyronine, and we found that induction of somatotrophs by corticosterone or by ACTH does not lead to increases in plasma insulin-like growth factor (IGF) I or II levels or hepatic IGF-I or II mRNA levels.
Impacts
Our research is directed at the hormonal control of growth in chickens. If we can understand this process better, we may be able to improve growth performance in this economically important species through novel approaches or through classical breeding.
Publications
- Bossis I, Porter TE (2003) Evaluation of glucocorticoid-induced growth hormone gene expression in embryonic pituitary cells using a novel in situ mRNA quantitation method. Mol Cell Endocrinol 201:13-23
- De Groef B, Geris KL, Manzano J, Bernal J, Millar RP, Abou-Samra AB, Porter TE, Iwasawa A, Kuhn ER, Darras VM (2003) Involvement of thyrotropin-releasing hormone receptor, somatostatin receptor subtype 2 and corticotropin-releasing hormone receptor type 1 in the control of chicken thyrotropin secretion. Mol Cell Endocrinol (in press)
- Cogburn LA,Wang X, Carre W, Rejto L, Porter TE, Aggrey SE, Simon J (2003) Systems-wide Chicken DNA Microarrays, Gene Expression Profiling and Discovery of Functional Genes. Poultry Science (in press)
- Liu L, Dean CE, Porter TE (2003) Thyroid Hormones Interact with Glucocorticoids to Affect Somatotroph Abundance in Chicken Embryonic Pituitary Cells In Vitro. Endocrinology (submitted)
- Jenkin SA, Richards MP, McMurtry JP, Porter TE (2003) Administration of Adrenocorticotropic Hormone (ACTH) During Chick Embryonic Development Induces the Premature Appearance of Growth Hormone Cells. J Endocrinol (submitted)
- Ghavam S, Muchow M, Porter TE (2002) Cloning of a partial cDNA for the chicken mineralocorticoid receptor. Program 84th Annual Meeting of the Endocrine Society.
- Fu X, Porter TE (2002) Differential timing for lactotroph and somatotroph induction by corticosterone in cultures of chicken embryonic pituitary cells. Program 84th Annual Meeting of the Endocrine Society.
- Liu L, Porter TE (2002) Thyroid hormones interact with glucocorticoids to affect somatotroph abundance during chick embryonic development. Program 84th Annual Meeting of the Endocrine Society.
- Muchow M, Porter TE (2002) Regulation of thyroid stimulating hormone (TSH) production in vivo during chicken embryonic development. Program 84th Annual Meeting of the Endocrine Society.
- Jenkins SA, Richards M, Porter TE (2002) Activation of adrenal corticosterone secretion in the chicken embryo and its effects on the growth hormone (GH)-insulin-like growth factor (IGF) axis. Program 35th Annual Meeting of the Society for the Study of Reproduction.
- Porter TE, Wang X, Carre W, Cogburn LA (2002) Expressed Sequence Tags (ESTs) from a Chicken Neuroendocrine System cDNA Library. Program 2002 Annual Meeting of the Poultry Science Association.
- Cogburn LA, Wang X, Carre W, Porter TE, Aggrey S, Simon J (2002) Systems-wide Chicken DNA Chips, Gene Expression Profiling and Discovery of Functional Genes. Program 2002 Annual Meeting of the Poultry Science Association.
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Progress 10/01/00 to 12/31/00
Outputs
The objectives from our proposal and prgress toward comleting them are as follows. 1) Evaluate potential mechanisms for corticosterone-induced GH cell differentiation. We determined that the regulation of GH induction in embryonic pituitary cells involves the induction of an unknown intermediate protein. 2) Determine somatostatin (SST) effects on GH secretion and somatotroph differentiation. We defined that the type 2 somatostatin receptor regulates GH secretion in chickens 3) Define involvement of the hypothalamo-pituitary-adrenal (HPA) and hypothalamo- pituitary-thyroid (HPT) axes in regulating GH cell differentiation. We found that treatment with the thyroid hormone synthesis inhibitor methimazole partially suppressed normal somatotroph differentiation. We determined that administration of ACTH in vivo increased the abundance of GH cells during embryonic development.
Impacts
An improved understanding of the regulation of growth in poultry will be helpful in developing novel approaches aimed at improving performance in this economically important species. Our research is aimed at understanding the hormonal systems controling growth in chickens.
Publications
- Bossis I, Porter TE (2000) Induction of GH mRNA by glucocorticoids in cultures of chicken embryonic pituitary cells. Program 92nd Annual Meeting of the American Society of Animal Science.
- Liu L, Porter TE (2000) Thyroid hormones regulate somatotroph abundance during chicken embryonic development. Program 92nd Annual Meeting of the American Society of Animal Science.
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