Effect of polyethylene glycol 400 on the pharmacokinetics and tissue distribution of baicalin by intravenous injection based on the enzyme activity of UGT1A8/1A9.

Baicalin (BG) is a bioactive flavonoid extracted from the dried root of the medicinal plant, Scutellaria radix (SR) (dicotyledonous family, Labiatae), and has several biological activities. Polyethylene glycol 400 (PEG400) has been used as a suitable solvent for several traditional Chinese medicines (TCM) and is often used as an excipient for the compound preparation of SR. However, the drug-excipient interactions between BG and PEG400 are still unknown. Herein, we evaluated the effect of a single intravenous PEG400 administration on the BG levels of rats using pharmacokinetic and tissue distribution studies. A liver microsome and recombinant enzyme incubation system were used to further confirm the interaction mechanism between PEG400 and UDP-glucuronosyltransferases (UGTs) (UGT1A8 and UGT1A9). The pharmacokinetic study demonstrated that following the co-intravenous administration of PEG400 and BG, the total clearance (CLz) of BG in the rat plasma decreased by 101.60% (p < 0.05), whereas the area under the plasma concentration-time curve (AUC)0-t and AUC0-inf increased by 144.59% (p < 0.05) and 140.05% (p < 0.05), respectively. Additionally, the tissue distribution study showed that the concentration of BG and baicalein-6-O-ß-D-glucuronide (B6G) in the tissues increased, whereas baicalein (B) in the tissues decreased, and the total amount of BG and its metabolites in tissues altered following the intravenous administration of PEG400. We further found that PEG400 induced the UGT1A8 and UGT1A9 enzyme activities by affecting the maximum enzymatic velocity (Vmax) and Michaelis-Menten constant (Km) values of UGT1A8 and UGT1A9. In conclusion, our results demonstrated that PEG400 interaction with UGTs altered the pharmacokinetic behaviors and tissue distribution characteristics of BG and its metabolites in rats.

Role of pepsin and pepsinogen: linking laryngopharyngeal reflux with otitis media with effusion in children.

OBJECTIVES/HYPOTHESIS: To analyze the relationship between laryngopharyngeal reflux (LPR) represented by pepsin and pepsinogen, and pathogenesis of otitis media with effusion (OME). STUDY DESIGN: Prospective case-control study. METHODS: Children with OME who required adenoidectomy and tympanostomy/tympanostomy tubes placement were enrolled in OME group, whereas children with adenoid hypertrophy (AH) who required adenoidectomy and individuals who required cochlear implantation (CI) were enrolled in AH and CI groups, respectively. Pepsinogen mRNA and protein levels were assessed by real-time fluorescence-based quantitative polymerase chain reaction and immunohistochemistry in adenoid specimens from the OME and AH groups. Pepsin and pepsinogen concentrations were evaluated by enzyme-linked immunosorbent assay in middle ear fluid and plasma from the OME and CI groups. RESULTS: The levels of pepsinogen protein expressed in cytoplasm of epithelial cells and clearance under epithelial cells in adenoid specimens from the OME group were significantly higher than those in the AH group. Furthermore, the concentrations of pepsin and pepsinogen in the OME group were 51.93±11.58 ng/mL and 728±342.6 ng/mL, respectively, which were significantly higher than those in the CI group (P<.001). In addition, the concentrations of pepsin in dry ears were significantly lower than those in serous and mucus ears in the OME group (F=22.77, P<.001).Finally, the concentration of pepsinogen in middle ear effusion was positively correlated with the expression intensity of pepsinogen protein in cytoplasm of epithelial cells (r=0.73, P<.05) in the OME group. CONCLUSIONS: Pepsin and pepsinogen in middle ear effusion are probably caused by LPR and may be involved in the pathogenesis of OME. LEVEL OF EVIDENCE: 3b.