ABSTRACT
OBJECTIVE To investigate the effect of hypoxia on the pharmacokinetic process of salidrosidein rats and to explore its underlying mechanisms. METHODS The Caco-2 cell monolayerwas exposed to 1% oxygen (O2) concentration for 24 h to build the hypoxiccell model. The transportation mode of salidroside was investigated with the aid of this hypoxia model by detecting the apparent permeability coefficient(Papp). Healthy Sprague Dawley (SD) rats were exposed to 9% O2 for 72 h for the construction of hypoxic rat model. Liver sample was subsequently collected from the hypoxic rats with an aim to identify enzymes responsible for salidroside metabolism. The expression levels of sali?droside-transporting and salidroside-metabolizing enzymes, including Sodium-dependent glucose cotrans?porters (SGLT1), β-glucosidase (GBA3)and sulfotransferase (SULT2A1), were thereafter detected by RT-PCR and Western blot. The metabolic activity of GBA3 and SULT2A1 was monitored by rat liver microsome incubation.In addition, the renal function of rats under hypoxia was assessed by detecting concentrations of blood urea nitrogen and creatinine. RESULTS The AUC and t1/2 values of salidroside in hypoxic rats were more than doubled, while the in vivo clearance was significantly reduced. Mechanistic study demonstrated that the PappA- B/PappB- A eualsto 10.3, indicating the potential active transport of salidrosile. The expression of SGLT1 and GBA3 was significantly decreased, which indicated a reduced metabolism of salidroside under hypoxia. Moreover, rat under hypoxia was found to suffer from renal dysfunction, with an abnormal value of blood urea nitrogen. CONCLUSION Due to the reduced metabolism and the abnormal renal function under hypoxia, the systemic exposure of salidroside in rats was signifi?cantly enhanced.
ABSTRACT
OBJECTIVE To map a comprehensive metabolic pathway of herbacetin in rats, specifically, to elucidate the biotransformation of herbacetin in vivo and to simultaneously monitor the pharmacokinetic process of both parent drug and its major metabolites. METHODS liquid chromatography/ion trap mass spectrometry (LC/MSn) and ultra-liquid chromatography coupled with mass spectrometry (UPLC/MS) were combined in the current study for qualitative and quantitative determinations of herbacetin and its metabolites in bile, urine and feces after both oral and intravenous administration of herbacetin to rats. Enzyme kinetic studies on the intestinal and hepatic metabolism of herbacetin were further conducted to elucidate metabolic profiles of herbacetin in rat tissues and organs. Additionally, plasma concentration profiles of herbacetin and its metabolites in rats were obtained to characterize the overall pharmacokinetic behavior of herbacetin. RESULTS It was found that herbacetin was excreted primarily from rat urine in the form of glucuronide-conjugations. Subsequent in vitro enzyme kinetic studies and in vivo pharmacokinetic investigations suggested an extensive hepatic metabolism of herbacetin and the high exposure of herbacetin- glucuronides in systemic circulation. The clearance, half- life and bioavailability of herbacetin in rats were determined as (16.4±1.92)mL·kg-1·min-1, (11.9±2.7)min, and 1.32%, respectively. On basis of these findings, a comprehensive metabolic pathway of herbacetin in rats was composed. In addition, a physiology based pharmacokinetic (PBPK) model was successfully developed with the aid of the GastroPlus to simulate the pharmacokinetic process of herbacetin in rats. Application of the PBPK modeling can provide a useful starting point to understand and extrapolate pharmacokinetic parameters among different species, populations, and disease states. CONCLUSION After oral administration, herbacetin was subjected to colonic degradation and extensive first pass metabolism, with glucuronidation as its dominating in vivo metabolic pathway.