Effects of estrogen on the cultured osteoclasts in vitro

Objective To study the effects of estrogen on the cultured osteoclasts in vitro. Methods The acid phosphatase (ACP) and tartrate resistant acid phosphatase (TRAP) activities were measured kinetically and the introcellular hydrogen ions were calculated with the confocal laser scanning microscopy(CLSM). The area and number of the resorption pits were determined with the Leica Quantimet 500 system. Bone resorption pits were observed with scanning electronicmicroscope. Results With the estrogen concentration increased, the ACP and TRAP activities decreased from (1 69±0 13) U/L and (1 60±0 14) U/L to (1 16±0 31) U/L and (0 93±0 34) U/L, respectively (experiment group vs control group, P 0 01) In addition, the area and number of the resorption pits reduced from (13 25±1 52) and (482 27±225 23)μm 2 to (4 68±0 24) and (356 35±145 41)μm 2 , respectively ( P 0 01). Conclusions Estrogen could not only inhibit hydrogen ions yielding, but also change ACP and TRAP activities, therefore inhibit the bone resorption by osteoclastes.