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IGF‐I Production by Mouse Osteoblasts
Author(s) -
Wong G. L.,
Kotliar D.,
Schlaeger D.,
Brandes S. J.
Publication year - 1990
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650050206
Subject(s) - endocrinology , medicine , secretion , calvaria , radioimmunoassay , biology , collagenase , growth factor , osteoblast , receptor , cell culture , bone cell , cell growth , in vitro , biochemistry , enzyme , genetics
Mouse osteoblasts contain and secrete insulinlike growth factor I (IGF‐I), which can be measured by radioimmunoassay after separation from endogenous IGF‐I binding activity. Our studies indicate that IGF‐I is produced by all bone cell populations prepared by sequential digestion of mouse calvaria with collagenase and protease. Furthermore, relatively small amounts of IGF‐I are cell associated, and IGF‐I is recovered primarily in the cell medium after 24 h of culture. Basal IGF‐I secretion is also density dependent, and secretion per cell is approximately 20‐fold higher when cultures are inoculated at 0.125 versus 1.0 × 10 5 cells per cm 2 . Growth hormone increased the secretion of IGF‐I only in cells released in the earlier stages of digestion. These growth hormone‐responsive populations were previously shown to differ from late released cells in that they show a lower expression of the osteoblastic phenotype, harbor more EGF receptors per cell, and have a higher proliferative response to low doses of exogenous IGF‐I and EGF. These data reaffirm the presence of different subclasses of bone cells in populations obtained by sequential digestion of bone and suggest that growth hormone stimulates IGF‐I secretion by immature osteoblasts