Inhibitory effect of an aqueous extract of Radix Paeoniae Alba on calcium oxalate nephrolithiasis in a rat model.

OBJECTIVE: To examine the effect of an aqueous extract of Radix Paeoniae Alba (RPA) on the formation of calcium oxalate (CaOx) stones and the potential mechanism underlying the effect. MATERIALS AND METHODS: An in vitro assay was used to determine whether the RPA extract prevents the formation of CaOx or promotes CaOx dissolution. We also investigated the efficacy of the extract in vivo as a preventive and therapeutic agent for experimentally induced CaOx nephrolithiasis in rats. Various biochemical, molecular, and histological parameters were assessed in kidney tissue and urine at the end of the in vivo experiment. RESULTS: Significant dissolution of formed crystals (8.99 ± 1.43) and inhibition of crystal formation (2.55 ± 0.21) were observed in vitro after treatment with 64 mg/mL of the RPA extract compared with a control treatment (55.10 ± 4.98 and 54.57 ± 5.84, respectively) (p < .05). In preventive protocols, the RPA extract significantly reduced urinary and renal oxalate levels and increased urinary calcium and citrate levels compared to the control. In addition, the RPA preventive protocol significantly decreased osteopontin expression, renal crystallization, and pathological changes compared to the control. These changes were not observed in rats on the therapeutic protocol. CONCLUSIONS: RPA is a useful agent that prevents the formation of CaOx kidney stones.