Regulation of insulin-like growth factor-I ribonucleic acid expression, polypeptide secretion, and binding protein activity by growth hormone in porcine preadipocyte cultures.
Insulin-like growth factor-I (IGF-I) is a mitogenic polypeptide postulated to mediate the effect of GH on adipose tissue development. To determine if the effect of GH could be mediated by the local production of IGF-I, we have characterized IGF-I RNA expression, polypeptide secretion, and binding protein activity in primary preadipocyte cultures derived from porcine adipose tissues. GH acutely regulated the abundance of multiple IGF-I RNA transcripts and resulted in a 2-fold increase in secreted immunoreactive IGF-I (iIGF-I) polypeptide in medium conditioned for 48 h by preadipocyte cultures relative to those not receiving GH. Immunocytochemical data indicated that IGF-I is synthesized by presumptive and mature adipocytes. The effect of GH on iIGF-I secretion was observed in cultures derived from both fetal and postnatal animals, while secreted IGF-binding protein activity was increased due to GH only in cultures from fetal animals. The increase in local IGF-I production in response to GH was associated with a decrease in adipocyte development, suggesting that local IGF-I may contribute to suppression of differentiated phenotype.
Gaskins
H R
HR
Department of Foods and Nutrition, University of Georgia, Athens 30602.
Kim
J W
JW
Wright
J T
JT
Rund
L A
LA
Hausman
G J
GJ
D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D015152:Blotting, Northern; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D003470:Culture Media; D013006:Growth Hormone / Q000378:metabolism; D007150:Immunohistochemistry; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D011863:Radioimmunoassay; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000235:genetics*; D013552:Swine; D014158:Transcription, Genetic
D003470:Culture Media; D010455:Peptides; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone