Objective: To study the effect of Saponins from Thladiantha dubia roots(TSTR) on serum levels of osteoprotegerin(OPG) and receptor activator of nuclear factor-κB ligand(RANKL) in serum of rat with rheumatoid arthritis(RA). Method: SD rats were randomly taken ten rats as blank control group

the rest of the rats were prepared to RA rat model

which was established by freund's complete adjuvant. RA model rats were randomly divided into model group

positive control group

high dosage TSTR group

middle dosage TSTR group and low dosage TSTR group.TSTR groups were fed with TSTR(40

80

160 mg·kg-1·d-1)

positive control group were fed with tripterygium(12 mg·kg-1·d-1). After intragastric administration for 21 days

serum levels of OPG and RANKL were evaluated by ELISA. Result: The levels of RANKL of the three TSTR groups (98.74±10.17)

(87.81±17.78)

(77.75±14.61) pmol·L-1 were significantly lower than the model group (120.80±12.14) pmol·L-1(P<0.05

P<0.01)

while the levels of OPG (71.67±2.62)

(77.50±0.93)

(91.04±7.26) pmol·L-1 were significantly higher than the model group (53.64±3.46) pmol·L-1(P<0.05

P<0.01). Compared to the model group (0.43±0.06)

the ratio of OPG/RANKL (0.71±0.08

0.89±0.17

1.13±0.24) were increased significantly in the three TSTR groups(P<0.05

P<0.01). Conclusion: The prevention and therapeutic effect of TSTR on rheumatoid arthritis may be via the up-regulation of OPG and down-regulation of RANKL. This would affect the function of osteoclast.