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OBJECTIVE: To establish a measuring method for microdialysis probe recovery of ginsenoside Rg1 and investigate the effects of flow rate, concentration and using times of probe on the recovery in vivo and in vitro. METHODS: Dialysis method and retrodialysis method were used for the study. The concentration of ginsenoside Rg1 in brain and blood dialysate was determined by LC-MS /MS and the probe recovery was calculated. RESULTS: The recoveries of brain and blood microdialysis probes showed good stability within 10 h, with average values of 17.0% and 34.4% respectively for ginsenoside Rg1 at 1.5 μL•min-1. Concentrations (50, 200, 500, 1 000 ng•mL-1) had no obvious effect on recovery. At the same concentration, the recovery of brain and blood probes for ginsenoside Rg1 decreased with the increase of flow rate (0.5, 1.0, 1.5, 2.0, 3.0 μL• min-1) in vitro and in vivo. The dialysis recoveries of brain and blood probes in vitro were (40.6 ± 4.3)%, (23.5 ± 2.3)%, (17.7 ± 0.8 )%, (12.2 ± 1.1)%, (8.8 ± 0.6)% and (70.6 ± 3.6)%, (46.0 ± 2.1)%, (32.9 ± 1.6)%, (25.6 ± 0.7)%, (18.2 ± 1.3)%, respectively. The recoveries of dialysis and retrodialysis in vitro were approximately equal, and the recovery detected by retrodialysis in vivo was similar with the in vitro results. Probe used for no more than 3 times still kept high transmittance by flushing with 2% heparin sodium and ultrapure water successively. CONCLUSION: Retrodialysis method can be used to study brain and blood probe recovery in vivo, and microdialysis can be used for simutaneous pharmacokinetic studies of ginsenoside Rg1 in intercelluar fluid and blood.
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OBJECTIVE: To determine the recovery rates of blood and brain microdialysis probes of acetylglutamine(NAG) and its decomposition products glutamic acid (Glu) and γ-aminobutyric acid (GABA) in vitro, and lay the foundation for the pharmacokinetic study of NAG in blood and brain. METHODS: The concentrations of NAG, Glu and GABA in blood and brain microdialysates were determined by LC-MS /MS and the probe recoveries were calculated. The in vitro recoveries of NAG, Glu and GABA were studied using positive dialysis and retrodialysis methods at different flow rates and concentrations. RESULTS: The in vitro recoveries of blood and brain probes of NAG, Glu and GABA were inversely proportional to the perfusate flow rates while independent of drug concentrations. The recovery rates obtained by positive dialysis and retrodialysis methods in vitro were approximately equal under the same condition, and were stable for at least 6 h. CONCLUSION: Retrodialysis method can be used to study the probe recovery of NAG, and microdialysis can be used for blood and brain pharmacokinetic study of NAG.
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OBJECTIVE: To evaluate the effects of drug concentration and perfusion rate on the recoveries of self-made linear microdialysis probes for further ocular pharmacokinetic study. METHODS :Brimonidine tartrate was selected as the model drug. The in vitro recovery was determined using positive dialysis and retrodialysis at different perfusion rates and drug concentrations. And the in vivo recovery was determined using retrodialysis method. RESULTS: The microdialysis recoveries of brimonidine tartrate were inversely proportional to perfusion rate,while independent of drug concentration. The positive dialysis and retrodialysis recoveries in vitro were different at 1.0 μL•min-1, but no significant difference at 2.0 and 3.0 μL•min-1. The in vitro recoveries were greater than those in vivo. CONCLUSION: The self-made microdialysis probe has stable recovery and can be used in ocular pharmacokinetic study of brimonidine tartrate.
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To further study the brain behavior and the pharmacokinetics of baicalin in intercellular fluid of brain, and study the recovery rate and stability of brain and blood microdialysis probe of baicalin in vitro and in vivo. The concentration of baicalin in brain and blood microdialysates was determined by LC-MS/MS and the probe recovery for baicalin was calculated. The effects of different flow rates (0.50, 1.0, 1.5, 2.0，3.0 μL•min⁻¹) on recovery in vitro were determined by incremental method and decrement method. The effects of different drug concentrations (50.00, 200.0, 500.0, 1 000 μg•L⁻¹) and using times (0, 1, 2) on recovery in vitro were determined by incremental method. The probe recovery stability and effect of flow rate on recovery in vivo were determined by decrement method, and its results were compared with those in in vitro trial. The in vitro recovery of brain and blood probe of baicalin was decreased with the increase of flow rate under the same concentration; and at the same flow rate, different concentrations of baicalin had little influence on the recovery. The probe which had been used for 2 times showed no obvious change in probe recovery by syringe with 2% heparin sodium and ultrapure water successively. In vitro recovery rates obtained by incremental method and decrement method were approximately equal under the same condition, and the in vivo recovery determined by decrement method was similar with the in vitro results and they were showed a good stability within 10 h. The results showed that decrement method can be used for pharmacokinetic study of baicalin, and can be used to study probe recovery in vivo at the same time.
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Aim To establish a LC-MS/MS method to measure the concentration of ginsenoside Rg1 in intrac-erebral dialysate and compare the probe recovery in vitro and in vivo. Methods The assay was conducted with a ACQUITY UPLC BEH C18(2. 1 mm × 50 mm, 1. 7 μm) . The mobile phase consisted of methanol and ultrapure water and it was detected by gradient elution. The flow rate was 0. 4 mL·min-1 . Specificity, linear range, precision and accuracy, stability were evaluated to investigate the reliability of the method. The recov-ery of ginsenoside Rg1 in probe in vitro and in vivo was compared. Results The retention time of ginsenoside Rg1 was 1. 91 min, the linear range was 0. 1 ~50 μg · L-1 , intra-day and inter-day precisions were less than 15%. The recovery of ginsenoside Rg1 was (4. 05 ± 0. 28)% in vitro and(26. 96 ± 4. 45)% in vi-vo. Conclusion The LC-MS/MS method is accurate, sensitive, and reproducible for quantitative determina-tion of ginsenoside Rg1 in microdialysate. The probe recovery of ginsenoside Rg1 in vivo is higher than in vitro, and both are stable in different concentrations.
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Objective To establish a method for determining the recovery of rocuronium microdialysis probe by LC-MS/MS, so as to investigate the stability and reproducibility of microdialysis probe recovery during in vivo and in vitro microdialysis trials and to provide evidence for in vivo microdialysis. Methods The concentration of rocuronium in dialysate was determined by LC-MS/MS and the probe recovery was calculated.The effects of different drug concentrations (50, 200, and 500 ng/mL) and flow rates(0.5, 1.0, 2.0, 3.0, and 4.0 μL/min)on the probe recovery were determined by incremental (dialysis) and reduction (retrodialysis) methods. The in vivo probe recovery in SD rats was determined by reduction method, and its result was compared with that of the in vitro trial. Results The in vitro probe recovery decreased with the increase of flow rate within a range of 0.5-4 μL/min under the same condition. At the same flow rate, different concentrations of rocuronium had little influence on the probe recovery. Under the same condition, the in vitro recovery obtained by incremental and reduction methods were approximately equal and showed a good stability. The in vivo probe recovery obtained by reduction method was similar to the in vitro one. Conclusion Microdialysis can be used for pharmacokinetic study of rocuronium, and retrodialysis method can be used to study probe recovery of rocuronium in vivo.
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OBJECTIVE: To evaluate the effects of drug concentration, perfusion rate and microdialysis method on the recoveries of concentric cannula and linear microdialysis probes.