Effect of saikosaponins on dexamethasone suppression of the pituitary-adrenocortical system.

Abstract

The effect of saikosaponins d and a on corticosterone secretion was investigated in dexamethasone-treated rats (250μg/kg, 0.64×10-6mol/kg, i.p. 3h before saponin injection). Plasma corticosterone level 30min after saponin injection was determined by the competitive protein binding method. Saikosaponins d and a both had no effect at low doses, but elevated plasma corticosterone levels at higher doses. ED50 values for corticosterone response to saikosaponins d and a were 1.4mg/kg (1.8×10-6mol/kg) and 3.8mg/kg (4.9×10-6mol/kg) in the dexamethasone-treated rats, and these values were 4.2 and 4.3 times greater than the ED50 values determined in rats without dexamethasone treatment, respectively.