Calcitonin increases the concentration of insulin-like growth factors in serum-free cultures of human osteoblast-line cells.
The current studies were intended to determine whether the anabolic effects of calcitonin (CT) on human osteoblast-line cells were (1) unique to osteosarcoma cells or also evident in osteoblast-line cells derived from normal human bone; and/or (2) associated with effects on several insulin-like growth factor (IGF) system components. Preliminary studies identified several osteoblastic cell lines, derived from normal human bone, which showed calcitonindependent increases in cell proliferation, alkaline phosphatase activity, and/or (45)Ca uptake (P < 0.05-P < 0.001). Two of these cell lines-(human vertebrae) HBV-155 and HBV-163-were included with the human osteosarcoma cell line, SaOS-2, in most of our subsequent studies of calcitonin effects on selected IGF system components: IGF-II, IGF-I, and IGF binding proteins -3, -4, and -5. The results of those studies revealed that a 48 hour exposure to salmon CT caused a dose-dependent (0.03-3 mU/ml) increase in the net extracellular level of IGF-II (r = 0.96, P < 0.01) in serum-free cultures of SaOS-2 cells, with a maximal 60% increase at the highest tested dose (P < 0.02). Similar effects were seen with HBV-163 cells (r = 0.90, P < 0.01) and HBV-155 cells (r = 0.55, P < 0.02). The effect of calcitonin on the extracellular level of IGF-II was biphasic with respect to time: it decreased at 6 hours (P < 0.005 and P < 0.001, for SaOS-2 cells and HBV-163 cells, respectively) and increased at 24 hours (P < 0.02 and P < 0.05). These calcitonin-dependent increases in the extracellular level of IGF-II were associated with parallel increases in IGF-I (P < 0.005 for SaOS-2 cells and P < 0.03 for HBV-163 cells), but calcitonin did not affect the extracellular level of transforming growth factor (TGF)-beta. The calcitonin-dependent changes in IGF-II were not associated with changes in the extracellular levels of IGF binding proteins -3, -4, or -5. Finally, our studies showed that two other members of the CT superfamily-CT gene-related peptide and amylin-did not mimic the effect of CT to increase the extracellular level of IGF-II. Together, these data demonstrate that human osteoblast-line cells derived from normal human bone can respond to CT, and that those responses can include CT dose- and time-dependent increases in the extracellular levels of IGF-I and IGF-II.</hea
Farley
J
J
Departments of Medicine and Biochemistry, Loma Linda University, Loma Linda, California, USA.
Dimai
H P
HP
Stilt-Coffing
B
B
Farley
P
P
Pham
T
T
Mohan
S
S
D000469:Alkaline Phosphatase / Q000378:metabolism; D002116:Calcitonin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D016895:Culture Media, Serum-Free; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D018969:Insulin-Like Growth Factor Binding Proteins / Q000187:drug effects / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000187:drug effects / Q000378:metabolism*; D007335:Insulin-Like Growth Factor II / Q000187:drug effects / Q000378:metabolism*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012516:Osteosarcoma / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014407:Tumor Cells, Cultured
D016895:Culture Media, Serum-Free; D018969:Insulin-Like Growth Factor Binding Proteins; D016212:Transforming Growth Factor beta; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D002116:Calcitonin; D004247:DNA; D000469:Alkaline Phosphatase; D002118:Calcium; D013936:Thymidine