TY - JOUR
T1 - IGF-I regulates pro-opiomelanocortin and GH gene expression in the mouse pituitary gland
AU - Honda, J.
AU - Manabe, Y.
AU - Matsumura, R.
AU - Takeuchi, S.
AU - Takahashi, S.
PY - 2003/7/1
Y1 - 2003/7/1
N2 - IGF-I is expressed in somatotrophs, and IGF-I receptors are expressed in most somatotrophs and some corticotrophs in the mouse pituitary gland. Our recent study demonstrated that IGF-I stimulates the proliferation of corticotrophs in the mouse pituitary. These results suggested that somatotrophs regulate corticotrophic functions as well as somatotrophic functions by the mediation of IGF-I molecules. The present study aimed to clarify factors regulating pituitary IGF-I expression and also the roles exerted by IGF-I within the mouse anterior pituitary gland. Mouse anterior pituitary cells were isolated and cultured under serum-free conditions. GH (0-5 or 1 μg/ml), ACTH (10-8 or 10-7 M), GH-releasing hormone (GHRH; 10-8 or 10-7 M), dexamethasone (DEX; 10-8 or 10-7 M) and estradiol-17β (E2; 10-11 or 10-9 M) were given for 24h. IGF-I mRNA levels were measured using competitive RT-PCR, and GH and pro-opiomelanocortin (POMC) mRNA levels were measured using Northern blotting analysis. GH treatment significantly increased IGF-I mRNA levels (1.5- or 2.1-fold). ACTH treatment did not alter GH and IGF-I mRNA levels. IGF-I treatment decreased GH mRNA levels (0.7-or 0.5-fold), but increased POMC mRNA levels (1.8-fold). GH treatment (4 or 8 μg/ml) for 4 days increased POMC mRNA levels. GHRH treatment increased GH mRNA levels (1.3-fold), but not IGF-I mRNA levels. DEX treatment significantly decreased IGF-I mRNA levels (0.8-fold). E2 treatment did not affect IGF-I mRNA levels. GH receptor mRNA, probably with GH-binding protein mRNA, was detected in somatotrophs, and some mammotrophs and gonadotrophs by in situ hybridization using GH receptor cDNA as a probe. These results suggested that IGF-I expression in somatotrophs is regulated by pituitary GH, and that IGF-I suppresses GH expression and stimulates POMC expression at the transcription level. Pituitary IGF-I produced in somatotrophs is probably involved in the regulation of somatotroph and corticotroph functions.
AB - IGF-I is expressed in somatotrophs, and IGF-I receptors are expressed in most somatotrophs and some corticotrophs in the mouse pituitary gland. Our recent study demonstrated that IGF-I stimulates the proliferation of corticotrophs in the mouse pituitary. These results suggested that somatotrophs regulate corticotrophic functions as well as somatotrophic functions by the mediation of IGF-I molecules. The present study aimed to clarify factors regulating pituitary IGF-I expression and also the roles exerted by IGF-I within the mouse anterior pituitary gland. Mouse anterior pituitary cells were isolated and cultured under serum-free conditions. GH (0-5 or 1 μg/ml), ACTH (10-8 or 10-7 M), GH-releasing hormone (GHRH; 10-8 or 10-7 M), dexamethasone (DEX; 10-8 or 10-7 M) and estradiol-17β (E2; 10-11 or 10-9 M) were given for 24h. IGF-I mRNA levels were measured using competitive RT-PCR, and GH and pro-opiomelanocortin (POMC) mRNA levels were measured using Northern blotting analysis. GH treatment significantly increased IGF-I mRNA levels (1.5- or 2.1-fold). ACTH treatment did not alter GH and IGF-I mRNA levels. IGF-I treatment decreased GH mRNA levels (0.7-or 0.5-fold), but increased POMC mRNA levels (1.8-fold). GH treatment (4 or 8 μg/ml) for 4 days increased POMC mRNA levels. GHRH treatment increased GH mRNA levels (1.3-fold), but not IGF-I mRNA levels. DEX treatment significantly decreased IGF-I mRNA levels (0.8-fold). E2 treatment did not affect IGF-I mRNA levels. GH receptor mRNA, probably with GH-binding protein mRNA, was detected in somatotrophs, and some mammotrophs and gonadotrophs by in situ hybridization using GH receptor cDNA as a probe. These results suggested that IGF-I expression in somatotrophs is regulated by pituitary GH, and that IGF-I suppresses GH expression and stimulates POMC expression at the transcription level. Pituitary IGF-I produced in somatotrophs is probably involved in the regulation of somatotroph and corticotroph functions.
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U2 - 10.1677/joe.0.1780071
DO - 10.1677/joe.0.1780071
M3 - Article
C2 - 12844338
AN - SCOPUS:0043172274
SN - 0022-0795
VL - 178
SP - 71
EP - 82
JO - Journal of Endocrinology
JF - Journal of Endocrinology
IS - 1
ER -
