Role of albumin in osteoblastic cells: enhancement of cell proliferation and suppression of alkaline phosphatase activity.
The role of albumin in osteoblastic cells was investigated. Osteoblastic MC3T3-E1 cells with subconfluent monolayers were cultured for 24 to 72 h in a medium without fetal bovine serum (FBS) in the presence or absence of albumin (0.25, 0.5, or 1.0 mg/ml of medium). The number of osteoblastic cells was significantly increased by culture for 24 to 72 h in the presence of albumin (1.0 mg/ml). The effect of albumin in increasing cell number was completely abolished in the presence of PD98049 (10(-7) M), staurosporine (10(-7) M), or dibucaine (10(-7) M), which is an inhibitor of various protein kinases. Also, the stimulating effect of albumin on cell proliferation was completely prevented in the presence of cycloheximide (10(-7) M), an inhibitor of protein synthesis, or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), an inhibitor of transcriptional activity. DNA content was significantly increased in the cells cultured with albumin (1.0 mg/ml) addition for 24 to 72 h. Alkaline phosphatase activity in the cells, which participates in osteoblastic calcification, was significantly decreased by the culture with albumin (0.25, 0.5, or 1.0 mg/ml) for 24 to 72 h. The expression of insulin-like growth factor-I (IGF-I) and transforming growth factor-beta1 mRNAs using transcription-polymerase chain reaction (RT-PCR) analysis in osteoblastic cells was not significantly altered by culture for 48 h with albumin (1.0 mg/ml). This study demonstrated that albumin had a role in the regulation of osteoblastic cell function.
Ishida
Koichi
K
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Shizuoka 422-8526, Japan.
Yamaguchi
Masayoshi
M
D000418:Albumins / Q000494:pharmacology*; D000469:Alkaline Phosphatase / Q000378:metabolism*; D000818:Animals; D002452:Cell Count; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D051379:Mice; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics; D053773:Transforming Growth Factor beta1
D000418:Albumins; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D007334:Insulin-Like Growth Factor I; D004247:DNA; D000469:Alkaline Phosphatase