Objective To investigate the effects in vitro of 17 β-estradiol (E2) on the proliferation and metabolism of rabbit mandibular condylar cartilage cells.Methods Chondrocytes were derived from neonatal rabbit mandibular condylar cartilage using a modified enzyme method. 17p-estradiol was added to the culture medium in a variety of concentrations. Cell growth and DNA, collagen, and proteoglycan synthesis were used as indicators of proliferation and differentiation of condylar chondrocytes. These were measured by cell number, 3H-proline and 35S-incorporation, respectively.Results E2 increased cell number and 3H-thymidine incorporation at 10~(-8) to 10~(-10)mol/L, and 10~(-8) to 10~(-11) mol/L in a dose-dependent manner, peaking at 10~(-8) mol/L and 10~(-9) mol/L, respectively. However, further increase in the concentration of estradiol caused inhibition of both cell number and 3H-thymidine incorporation, and this was significant at 10~(-6) mol/L. The effect of E2 on proteglycan synthesis was similar; the ma Objective To investigate the effects in vitro of 17 β-estradiol (E2) on the proliferation and metabolism of rabbit mandibular condylar cartilage cells. Methods Chondrocytes were derived from neonatal rabbit mandibular condylar cartilage using a modified enzyme method. 17p-estradiol was added to the Culture medium in a variety of concentrations. Cell growth and DNA, collagen, and proteoglycan synthesis were used as indicators of proliferation and differentiation of condylar chondrocytes. These were measured by cell number, 3H-proline and 35S-incorporation, respectively. Results. cell number and 3H-thymidine incorporation at 10 ~ (-8) to 10 ~ (-10) mol / L and 10 ~ (-8) to 10 ~ (-11) mol / L in a dose- dependent manner, at 10 ~ (-8) mol / L and 10 ~ (-9) mol / L, respectively. However, further increase in the concentration of estradiol caused inhibition of both cell number and 3H-thymidine incorporation, and this was significant at 10 ~ (-6) mol / L. The effect of E2 on proteglycan synthesis w as similar; the ma