ObjectivesThe study focuses on the establishment of diabetic rat model by inducing with streptozotocin and the investigation of the stability of rat model, the effects of Yuquan pill on the hypoglycemic activity and pharmacokinetics of metformin in rats. Simultaneously, the effect of Yuquan pill on the activity of cytochrome P450 was investigated in rats.MethodsThe diabetic rat model was induced by peritoneal injecting 60 mg·kg~(-1) streptozotocin. The rats, which the value of blood glucose exceeded 16.9 mmol·l~(-1) determined with the glucose oxidase method, were selected as diabetic model rat. Simultaneously, the stability of rat model was investigated during 14 days.As for the hypoglycemic experiment, forty of diabetic model rats were randomly divided into diabetic model group (treated with normal saline 10 ml·kg~(-1)·d~(-1)), metformin (350 mg·kg~(-1)·d~(-1)) treated group, Yuquan pill (6.0 mg·kg~(-1)·d~(-1)) treated group, and Yuquan pill co-administration metformin treated group. All rats were oral administrated corresponding drugs with 7 days according the divided groups. After oral administration different drugs, the blood of rats was collected to determine the level of blood glucose at 1, 3, 5, 7, 10 and 14 day. Simultaneously, other ten of normal rats were selected as control group. The blood glucose value of rats in every group was regarded as the standard for evaluation the effect of Yuquan pill on the hypoglycemic activity of metformin.As for the pharmacokinetics study, ten of diabetic rats model were randomly divided into normal saline treated group (10 ml·kg~(-1)·d~(-1)) and Yuquan pill treated group (6.0 mg·kg~(-1)·d~(-1)), which were selected to study on the effects of Yuquan pill on the pharmacokinetics of metformin. After oral administration Yuquan pill and normal saline for 7 days, metformin was administrated at a dose of 350 mg·kg~(-1) at eighth day. The blood of rats was collected from femoral artery at special time. The concentration of metformin in plasma was determined using HPLC. In addition, the curve of concentration versus time was drawn, and the main pharmacokinetics parameters of metformin were calculated with the software of DAS1.0. The pharmacokinetics parameters of metformin in two group rats were regarded as the standard for evaluation the effect of Yuquan pill on the pharmacokinetics of metformin.As for the last part, 32 of normal rats were randomly divided into normal saline treated group (10 ml·kg~(-1)·d~(-1)), Yuquan pill treated group (6.0 g·kg~(-1)·d~(-1)), enzyme inducing group (treated with cimetidine 40 mg·kg~(-1)·d~(-1)), and enzyme inhibiting group (treated with phenobarbital sodium 3.0 mg·kg~(-1)·d~(-1)). After oral administration of corresponding drugs for 7 day, phenacetin (probe drug) was administrated by peritoneal injection at a dose of 40 mg·kg~(-1). The concentration of phenacetin in rat plasma was determined by HPLC, and the pharmacokinetics parameters of phenacetin were calculated with the software of DAS1.0. The difference of t_(1/2) value of phenacetin were compared in each group and regarded as the standard for evaluation the effect of Yuquan pill on the activity of cytochrome P450 in rats.ResultsAfter 3 days for peritoneally injecting of 60 mg·kg~(-1) streptozotocin, the achievement ratio of model was 75%, and the average value of blood glucose in rats was 19.46±1.53 mmol·l~(-1). The diabetic rat model was stable during 14 days.After co-administrating Yuquan pill and metformin 7 days, the blood glucose value of co-administration treated group rats were clearly decrease to 9.65±1.66 mmol·l~(-1). There had a significant difference compared with the blood glucose of model group rats (p0.05).ConclusionsUsing streptozotocin for inducing the diabetic rat model, the mortality of rats was low, and the stability of diabetic model was satisfactory. Streptozotocin could be regarded as an excellent inductor for inducing the diabetic rat model.There was no synergistic effect between Yuquan pill and metformin in the hypoglycemic activity. Furthermore, it seemed that Yuquan pill could inhibit the hypoglycemic activity of metformin, which may reduce the incidence rate of hypoglycemia. Moreover, Yuquan pill could reparir the injured kidney of the diabetic rat model.After Yuquan pill co-administration with metformin, the active component of Yuquan pill may compete with metformin in glomerular filtration, which resulted in an accumulation of metformin in rats. Consequently, Yuquan pill should influence on the pharmacokinetics of metformin in rats.Yuquan pill may induce the activity of cytochrome P450 in rats.