RESUMEN
BACKGROUND: There are plenty of studies of estrogen effects on mammalian osteoblast, but the studies of estrogen effects on bird osteoblast cannot be found. There are many reports about the side effects of letrozole on bone metabolism, but there are no reports about the effect of letrozole on osteoblast.OBJECTIVE: The effects of estrogen and letrozole on the proliferation, cell cycle, estrogen receptor mRNA expression and alkaline phosphatase (ALP) activity of chicken osteoblast in vitro were studied in order to illustrate the mechanism of medullary bone osteogenesis.METHODS: The osteoblasts were harvested from the frontal bone of 15-day SPF chicken embryos by the enzyme digestion, and treated with various mass concentrations of estrogen (0, 5, 10, 20, 100. 200, 400,800, 2 000, 20 000 ng/L) and letrozole (0, 5.10, 25, 50, 100, 250, 500, 1 000, 5 000 μg/L). The proliferation rates of the osteoblast treated with estrogen or letrozole were measured through the MTT method, The ALP activities of osteoblast were measured by the pNPP method. The cell cycle was measured by flow cytometry. The expression of estrogen receptor mRNA was detected using real-time fluorescent quantitative polymerase chain reaction (PCR).RESULTS AND CONCLUSION: The estrogen could promote proliferation of osteoblast in concentration- and time-dependent fashion. Estrogen could increase the expression of estrogen receptor mRNA, impulse cell cycle, and elevate ALP activities.Letrozole could increase the cell population, impulse cell cycle, inhibit estrogen receptor mRNA expression, but letrozole has no effects on ALP synthesis and secretion.