OBJECTIVETo study the effect of aldosterone on cell proliferation, alkaline phosphatase (AKP) activity and osteogenic gene expression in rat osteoblasts and explore the mechanisms.

METHODSOsteoblasts isolated from the skull of neonatal SD rats by enzyme digestion were cultured and treated with different concentrations of aldosterone. The cell proliferation and AKP activity were evaluated using CCK-8 assay kit and AKP assay kit, respectively. The effects of aldosterone on mRNA and protein expressions of the osteogenic genes and epithelial sodium channel (ENaC) gene were investigated using semi-quantitative PCR and Western blotting.

RESULTSCompared with the control cells, the cells treated with 0.01-1.0 µmol/L aldosterone showed obviously enhanced proliferation while lower (1×10µmol/L) or higher (10 µmol/L) concentrations of aldosterone did not significantly affect the cell proliferation. Aldosterone within the concentration range of 1×10to 10 µmol/L did not cause significant changes in AKP activity in the osteoblasts. Treatment with 0.01 to 1.0 µmol/L aldosterone significantly upregulated the expressions of the osteogenic genes and α-ENaC gene at both the mRNA and protein levels.

CONCLUSIONAldosterone within the concentration range of 0.01-1.0 µmol/L stimulates the proliferation and osteogenic gene expressions and enhances α-ENaC gene expression in rat osteoblasts in vitro, suggesting the possibility that ENaC participates in aldosterone-mediated regulation of osteoblast functions.