ABSTRACT
OBJECTIVE： To establish a method for the determination of related substances in rifabutin crude drug and capsules by HPLC. METHODS： HPLC method was adopted. The determination was performed on Agilent XDB-C8 column with mobile phase consisted of acetonitrile-0.1 mol/L potassium dihydrogen phosphate solution （pH 6.5±0.1） （50 ∶ 50， V/V） at the flow rate of 1.0 mL/min. The detection wavelength was set at 254 nm， the column temperature was 30 ℃， and sample size was 20 μL. The mobile phase was used as solvent to prepare the sample solution with a mass concentration of 1.0 mg/mL. The system suitability test was performed by using newly established method and current method （mass concentration of sample solution 0.5 mg/mL， C18 column） stated in quality standard of rifabutin crude drug and capsules. Related substance test was conducted for 6 batches of rifabutin crude drug and capsule （peak area normalization method）. RESULTS： The linear range of rifabutin was 0.8-16 μg/mL（r＝1.000 0）， RSDs of precision， reproducibility and stability tests （12 h） were all lower than 2.0％ （n＝6）； the limits of detection and quantification were 0.025 4， 0.085 2 μg/mL. In system suitability test， by using new method and current method， separation degree of rifabutin peak and pre-degradation product peak were 7.50 and 3.47. When 6 batches of samples were determined， the number of impurities detected by this method was 1-5 more than that by the current method， and the total amount of impurities was 0.19％-0.55％ higher. CONCLUSIONS： Established new method is well-separated and sensitive， and can be used for the determination of related substance in rifabutin crude drug and capsules， which helps the quality control of drugs.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the effects of angiotensin II type 1 receptor (AT1R) knockdown on the first-phase insulin secretion in isolated islets of db/db mice and explore the possible mechanisms.</p><p><b>METHODS</b>Islets were isolated from db/db and db/m mice and the expression level of AT1R in the islets was assayed. A recombinant adenovirus containing siRNA targeting AT1R (Ad-siAT1R) and a recombinant adenovirus with nonspecific siRNA (Ad-siControl) were constructed to infect the isolated islets for 72 h. AT1R, GLUT-2, and GCK expressions in the islets were investigated and islet perifusion was performed to evaluate the kinetics of insulin release.</p><p><b>RESULTS</b>The expression level of AT1R in the isolated islets from db/db mice was twice that of islets from db/m mice. The islets treated with Ad-siAT1R showed significantly decreased AT1R mRNA and protein levels and significantly increased expression of GLUT-2 (by 190%) and GCK (by 121%) compared to those treated with Ad-siControl (P<0.05). In response to stimulation with 16.7 mmol/L glucose, the first-phase insulin secretion was impaired in both Ad-siControl group and mock infected group with the peak insulin levels only 1.8 times of the basal level; the first-phase insulin secretion was markedly improved in islets treated with Ad-siAT1R, with a peak insulin level reaching 2.8 times of the basal level.</p><p><b>CONCLUSIONS</b>In isolated islets of db/db mice, selective AT1R inhibition can restore the first phase insulin secretion by up-regulating GLUT-2 and GCK, which may be one of the potential mechanisms by which AT1R blockers improve insulin secretion function.</p>