The effect of La~(3+) on formation of osteoclast-like cells in rabbit bone marrow cells induced by 1,25-dihydroxyvitamin D_3 and their bone-resorbing activity was evaluated by counting the number of tartrate resistant-acid phosphatase-positive [TRAP(+)] multi-nucleated cells and measuring the number and surface area of bone resorption pits with photomicrography and image analysis. The formation and morphological characteristics of osteoclast-like cells and bone resorption pits were observed under a phase contrast inverted microscope. La~(3+) promotes the formation of osteoclast-like cells at the concentration of 1.00×10~(-8)mol·L~(-1) compared with the control group(P<(0.01)), whereas no significant change in cell number is observed at higher concentrations(1.00×10~(-5), (1.00×)10~(-6) and 1.00×10~(-7) mol·L~(-1))(P>0.05). La~(3+) at the concentration of 1.00×10~(-8)mol·L~(-1) also increases the number and surface area of the resorption pits(P<0.01), but inhibits the bone-resorbing activity dose-dependently(P<0.01)at higher concentrations(1.00×10~(-5), 1.00×10~(-6) and 1.00×10~(-7) mol·L~(-1)). These findings suggest that La~(3+) may promote or inhibit the formation and bone-resorbing activity of osteoclast-like cells depending on its concentration.
lanthanum; osteoclast-like cells; 1, 25-dihydroxyvitamin D_3; bone marrow cells; bone resorption; rare earths
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