Differentiation of adipocyte precursors in a serum-free medium is influenced by glucocorticoids and endogenously produced insulin-like growth factor-I.
Stromal vascular cells from rabbit perirenal adipose tissue differentiated at a high frequency in a chemically-defined serum-free medium containing insulin, transferrin, tri-iodothyronine and dexamethasone. The omission from the culture medium of dexamethasone resulted in a lack of adipose conversion. Addition of IGF-I increased glycerol-3-phosphate dehydrogenase (GPDH) activity. The conditioned media from adipocyte precursor cells contained measurable quantities of immunoreactive IGF-I as determined by RIA after neutralization of IGF binding proteins interference. Dexamethasone increased IGF-I secretion during the first seven days after plating and decreased IGF-I binding to conditioned media. Three molecular forms of IGF binding proteins (IGFBPs) were identified by Western ligand blots in conditioned media, with M(r) = 40,000, 29,000 and 25,000. The major form (M(r) = 29,000) was decreased by dexamethasone. In contrast, the M(r) = 24,000 form was increased. Specific binding of 125I-labelled IGF-I to rabbit adipocyte precursor cells was more effectively inhibited by unlabelled IGF-I than by unlabelled IGF-II or insulin. The electrophoretic migration of cross linked 125I-IGF-I to microsomal membranes revealed a complex with M(r) = 130,000 under reducing conditions corresponding to the alpha-subunit of the IGF-I receptor. The addition of IGF-I monoclonal antibody to rabbit adipocyte precursor cells cultured in serum-free medium significantly inhibited [3H]-thymidine incorporation and significantly decreased (50%) GPDH specific activities. This inhibitory effect was overcome by the addition of exogenous IGF-I. Thus stromal vascular cells isolated from perirenal adipose tissue secrete IGF-I and IGFBPs, possess IGF-I receptors and respond to exogenous and endogenous IGF-I.(ABSTRACT TRUNCATED AT 250 WORDS)
Nouguès
J
J
Institut National de la Recherche Agronomique, Unité Différenciation Cellulaire et Croissance, Montpellier, France.
Reyne
Y
Y
Barenton
B
B
Chery
T
T
Garandel
V
V
Soriano
J
J
D000273:Adipose Tissue / Q000166:cytology*; D000818:Animals; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D003470:Culture Media; D017077:Culture Media, Conditioned; D003907:Dexamethasone / Q000494:pharmacology*; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins; D007334:Insulin-Like Growth Factor I / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D011817:Rabbits; D013234:Stem Cells / Q000166:cytology*; D014168:Transferrin / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D003470:Culture Media; D017077:Culture Media, Conditioned; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D014168:Transferrin; D014284:Triiodothyronine; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone; D005993:Glycerolphosphate Dehydrogenase