Sprague-Dawley Rat Plasma Research Articles

Pharmacokinetic study and neuropharmacological effects of atractylenolide Ⅲ to improve cognitive impairment via PI3K/AKT/GSK3β pathway in intracerebroventricular-streptozotocin rats

Ethnopharmacological relevanceThe traditional Chinese herbal remedy Atractylodes macrocephala Koidz is renowned for its purported gastrointestinal regulatory properties and immune-enhancing capabilities. Atractylenolide III (ATL III), a prominent bioactive compound in Atractylodes macrocephala Koidz, has demonstrated significant pharmacological activities. However, its impact on neuroinflammation, oxidative stress, and therapeutic potential concerning Alzheimer's disease (AD) remain inadequately investigated.Aim of the study: This study aims to assess the plasma pharmacokinetics of ATL III in Sprague-Dawley (SD) rats and elucidate its neuropharmacological effects on AD via the PI3K/AKT/GSK3β pathway. Through this research, we endeavor to furnish experimental substantiation for the advancement of novel therapeutics centered on ATL III. Materials and methodsThe pharmacokinetic profile of ATL III in SD rat plasma was analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). AD models were induced in SD rats through bilateral intracerebroventricular (ICV) administration of streptozotocin (STZ). ATL III was administered at doses of 0.6 mg/kg, 1.2 mg/kg, and 2.4 mg/kg, while donepezil (1 mg/kg) served as control. Cognitive function assessments were conducted employing behavioral tests including the Morris Water Maze and Novel Object Recognition. Neuronal pathology and histological changes were evaluated through Nissl staining and Hematoxylin-Eosin (HE) staining, respectively. Oxidative stress levels were determined by quantifying malondialdehyde (MDA) content and total superoxide dismutase (T-SOD) activity. Molecular docking analysis was employed to explore the direct binding between ATL III and its relevant targets, followed by validation using Western blot (WB) experiments to assess the expression of p-Tau, PI3K, AKT, GSK3β, and their phosphorylated forms. ResultsWithin the concentration range of 5–500 ng/mL, ATL III demonstrated exceptional linearity (R2 = 0.9991), with a quantification limit of 5 ng/mL. In male SD rats, ATL III exhibited a Tmax of 45 min, a t1/2 of 172.1 min, a Cmax of 1211 ng/L, and an AUC(0-t) of 156031 ng/L*min. Treatment with ATL III significantly attenuated Tau hyperphosphorylation in intracerebroventricular-streptozotocin (ICV-STZ) rats. Furthermore, ATL III administration mitigated neuroinflammation and oxidative stress, as evidenced by reduced Nissl body loss, alleviated histological alterations, decreased MDA content, and enhanced T-SOD activity. Molecular docking analyses revealed strong binding affinity between ATL III and the target genes PI3K, AKT, and GSK3β. Experimental validation corroborated that ATL III stimulated the phosphorylation of PI3K and AKT while reducing the phosphorylation of GSK3β. ConclusionsOur results indicate that ATL III can mitigate Tau protein phosphorylation through modulation of the PI3K/AKT/GSK3β pathway. This attenuation consequently ameliorates neuroinflammation and oxidative stress, leading to enhanced learning and memory abilities in ICV-STZ rats.

HPLC-MS/MS Method for the Quantitative Determination of Metformin in Rat Plasma and Its Application to Comparative Bioavailability Assessment

Background: Metformin is a biguanide derivative utilized as a first-line treatment for type 2 diabetes for people over 60 years. However, it faces certain limitations due to its incomplete absorption, resulting in a 50-60% bioavailability. In addition to its blood glucose-lowering effect, the antiproliferative effect of metformin has been demonstrated in vitro. Therefore, it is necessary to consider alternative administration routes that can enhance the bioavailability of metformin, expanding its clinical use beyond its role as an antidiabetic agent. Objective: The aim of the study was to develop a reliable bioanalytical method for the quantitation of metformin in male Sprague-Dawley rat plasma and explore the promising alternative administration route for metformin use. Methods: A robust, high-performance liquid chromatography-tandem mass spectrometry method for the quantification of metformin in rat plasma was developed and validated according to the latest regulatory guidance for bioanalysis. Results: Based on the area under the curves obtained from the rat pharmacokinetic study, subcutaneous injection increased the systemic exposure of metformin by 1.79-fold compared to oral administration in rats. Conclusion: Subcutaneous administration of metformin enhances its bioavailability compared to oral administration, leading to increased antidiabetic effects and potential antitumor activity.

Pharmacokinetics, tissue distribution, and excretion study of GL-V9 and its glucuronide metabolite 5-O-glucuronide GL-V9 in Sprague-Dawley rats.

The objective of this study is to explore the pharmacokinetics, tissue distribution, and excretion patterns of GL-V9 and its glucuronide metabolite, 5-O-glucuronide GL-V9, following the administration of GL-V9 to Sprague-Dawley (SD) rats. In this research, we developed and validated rapid, sensitive, and selective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) methods for quantifying GL-V9 and 5-O-glucuronide GL-V9 in various biological samples, including SD rat plasma, tissue homogenate, bile, urine, and feces. Quantification of GL-V9 and 5-O-glucuronide GL-V9 in plasma, tissue homogenate, bile, urine, and feces was performed using the validated LC-MS/MS methods. The bioavailability of GL-V9 in SD rats ranged from 6.23% to 7.08%, and both GL-V9 and 5-O-glucuronide GL-V9 exhibited wide distribution and rapid elimination from tissues. The primary distribution tissues for GL-V9 and 5-O-glucuronide GL-V9 in rats were the duodenum, liver, and lung. GL-V9 was predominantly excreted in urine, while 5-O-glucuronide GL-V9 was primarily excreted in bile. GL-V9 exhibited easy absorption and rapid conversion to its glucuronide metabolite, 5-O-glucuronide GL-V9, following administration.

Establishment and optimization of a high-throughput UPLC-MS/MS method for the simultaneous quantitation of cycloicaritin and its valine carbamate prodrug in rat plasma

An ultra-performance liquid chromatography-tandem mass spectrometry was developed to assay the concentration for the quantification of cycloicaritin and its carbamate prodrug (3-O-L-valyl carbamate prodrug of cycloicaritin) in the plasma of Sprague-Dawley rats. Analytes were separated on an Acquity UPLC BEH C18 (2.1 × 50 mm, 1.7 μm) after liquid–liquid extraction with methyl tert-butyl ether. Acetonitrile and water containing 0.1 % formic acid were the mobile phases of the method. Using electrospray ionization in the positive ion mode, the method was performed with a total run time of 2.60 min. The response of the experiments was linear over the concentration ranges from 1 to 250 ng/mL for cycloicaritin and 1–250 ng/mL for prodrug. The intra- and inter-day precision and accuracy were within the recommended limits of the FDA. The matrix effect that we observed met the criteria. The method was successfully applied to the pharmacokinetics of cycloicaritin and its carbamate prodrug in Sprague-Dawley rats.

The Effect of Dihydromyricetin on the Pharmacokinetics of Fluconazole in Sprague-Dawley Rat Plasma, Based on High-Performance Liquid Chromatography-Tandem Mass Spectrometry.

The synergistic effect of dihydromyricetin (DHM) and fluconazole (FLC) can improve the killing effect of FLC-resistant Candida albicans in vitro and in vivo. However, it is not clear whether DHM affects the pharmacokinetic characteristics of FLC. In this study, 12 Sprague-Dawley (SD) rats were randomly divided into two groups as follows: (1) an FLC group in which rats were administered FLC only (42 mg/kg orally); (2) an FLC with the combined administration of DHM group, in which rats received an equivalent FLC dose immediately following the administration of DHM (100 mg/kg). Blood samples were collected from the ocular choroid vein of rats and converted into plasma. The concentrations of FLC in the rat plasma were then determined by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), and the related pharmacokinetic parameters were analysed. The initial mobile phase included 0.1% acetonitrile and water with gradient elution. Multiple reaction monitoring modes of m/z 307.2→220.1 for FLC, and m/z 237.1→194.2 for carbamazepine, were utilised to conduct quantitative analysis. The calibration curve of FLC in rat plasma demonstrated good linearity in the range of 0.1-30 μg/mL (r > 0.99), and the lower limit of quantification was 0.1 μg/mL. Moreover, the intra- and inter-day precision relative standard deviation of FLC was less than 9.09% and 6.51%, respectively. There were no significant differences in the pharmacokinetic parameters between the two groups. The results showed that DHM administration did not significantly alter FLC pharmacokinetics in SD rat plasma.

A simple LC-MS/MS method for simultaneous determination of cilostazol and ambroxol in Sprague-Dawley rat plasma and its application to drug-drug pharmacokinetic interaction study following oral delivery in rats

Recently, a combination of cilostazol and ambroxol has been used in the clinical treatment of stroke-associated pneumonia (SAP). However, the pharmacokinetic drug-drug interaction (DDI) of cilostazol and ambroxol has not been reported. In this paper, a rapid, reproducible and sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) method for simultaneous determination of cilostazol and ambroxol in Sprague-Dawley (SD) rat plasma was established and validated for the first time. Domperidone was used as the internal standard (IS) and one-step liquid–liquid extraction (LLE) method was used to extract analytes and IS from plasma samples with methyl tert-butyl ether as extractant. A rapid chromatographic separation within 4.8 min was carried on an Ultimate ® XB-C18 column with a mobile phase consisting of methanol–acetonitrile-formic acid (0.1%) aqueous solution (90:2:8, v/v/v) at a flow rate of 500 μL/min. The quantitative detection of the analytes and IS were performed on a positive electrospray ionization mode (ESI), and scanned by multi-reaction monitoring (MRM) with the ion transitions m/z 370.3 → m/z 288.2 for cilostazol, m/z 378.8 → m/z 263.8 for ambroxol and m/z 426.2 → m/z 175.1 for domperidone (IS), respectively. It had good linearity in the range of 5.0–1000 ng/mL for cilostazol and 1.0–200 ng/mL for ambroxol in rat plasma. The methodology was fully validated with selectivity, linearity, lower limits of quantification, precision, accuracy, extraction recovery, matrix effect, stability and carry-over effect. The validated data have met the determination requirements of biological samples in FDA guideline. The method was successfully applied to the pharmacokinetics and DDI study of cilostazol and ambroxol in male SD rats. The current study found that the interaction between cilostazol and ambroxol may be caused by CYP3A4 and the pharmacological properties of cilostazol, which may be helpful for therapeutic drug monitoring, clinical dose reference and provide a valuable tool for drug-drug interactions.

Effects of Bisphenol A and Bisphenol S Exposure at Low Doses on the Metabolome of Adolescent Male Sprague-Dawley Rats.

Toxic effects induced upon exposure to low-dose bisphenol A (BPA) or bisphenol S (BPS) remains controversial. In this study, metabolomics was used to examine the metabolomic perturbation arising from 28 days of exposure to BPA or BPS at 50 μg/kg bw/day in Sprague-Dawley (SD) rats. Endogenous metabolite profiling revealed a clear discrimination of metabolome in the rat plasma among BPA-treatment, BPS-treatment, and control groups. BPA exposure induced the up-regulation of 19 metabolites and down-regulation of 32 metabolites in plasma of SD rats, compared with the control. BPS exposure induced the up-regulation of 15 metabolites and the down-regulation of 33 metabolites in the plasma of SD rats, compared with the control. Joint pathway analysis suggested marked perturbations in the citrate cycle, butanoate metabolism, and alanine, aspartate, and glutamate metabolism for BPA-exposed rats as well as glycerophospholipid metabolism for BPS-exposed rats. These findings provide novel insights into associations between the metabolomic perturbation and phenotypic changes arising from BPA and BPS exposure.

A rapid LC-MS/MS method for simultaneous determination of berberine and irbesartan in rat plasma: Application to the drug-drug pharmacokinetic interaction study after oral administration in rats.

A sensitive, reproducible, and specific liquid chromatography tandem mass spectrometry method was developed and validated to simultaneously determine the concentration of berberine (BBR) and irbesartan in Sprague-Dawley rat plasma, and applied to study the pharmacokinetic drug-drug interaction (DDI) between BBR and irbesartan in rats. In this method, diphenhydramine was used as the internal standard, and the liquid-liquid extraction method using ethyl acetate as the extraction agent was used for sample preparation. After extraction, the prepared samples were run on an Agilent Welchrom C18 column with the mobile phase consisting of methanol-acetonitrile-water solution with 0.5% formic acid (45:50:5, v/v/v) at a flow rate of 0.8 mL·min-1 . The analytes BBR, irbesartan, and diphenhydramine (IS) were detected using multiple reactions monitoring mode, with the ion transitions being m/z 336.1 → m/z 320.0, m/z 429.1 → m/z 206.9, and m/z 256.2 → m/z 167.0, respectively. In the rats' plasma, BBR had good linearity in the range of 0.5-100 ng·mL-1 with the lower limit of quantitation of 0.5 ng·mL-1 , and the accuracy, intra-day, and inter-day precision were less than 12.33%. Irbesartan had good linearity in the range of 20-1200 ng·mL-1 with the lower limit of quantification of 20 ng·mL-1 , and the accuracy, intra-day, and inter-day precision were less than 13.55%. The validated method was verified to meet the determination requirements of biological samples. It was the first time to study the pharmacokinetics of DDI between BBR and irbesartan successfully, which would be necessary and beneficial to explore the clinical safety and efficacy of the combination of BBR and irbesartan in the treatment of diabetic nephropathy.

Potential Biomarkers for Early Detection of 3-MCPD Dipalmitate Exposure in Sprague-Dawley Rats.

3-Chloro-1,2-propandiol (3-MCPD) dipalmitate is one of the major 3-MCPD esters formed during food processing. In this single-dose study, the metabonomic profile changes in the 48 h after orally administrated 3-MCPD dipalmitate at 1600 mg/kg BW to Sprague-Dawley (SD) rats were determined with liquid chromatography (LC) coupled with mass spectrometry (MS) system. The chemical structures of 12 potential biomarkers for 3-MCPD dipalmitate exposures early detection were detected and tentatively identified from the plasma of SD rats, including indoxyl sulfate, phenol sulfate, p-cresol sulfate, 2-phenylethanol glucuronide, p-cresol glucuronide, p-cresol, allantoin, phenylacetylglycine, pyrocatechol sulfate, phenyllactic acid, 5-hydroxyindoleacetic acid, and creatinine. Taking into account the metabolites identified from SD rats' kidney, liver, testes, and spleen samples, 3-MCPD dipalmitate might potentially disturb the phenylalanine, tryptophan, tyrosine, glycine, fatty acid, and purine metabolisms. The results suggested that the 12 plasma metabolites could be potentially applied in detecting the early exposures of 3-MCPD esters.

The experimental application of steam explosion-pre-treated flaxseed meal with hypoglycaemic and lipid-lowering functions in rats on a high-fat-sugar diet

With the increase in populations with suboptimal health and chronic diseases, consumer demands for health foods, especially food products with health functions. The flaxseed was a complex mixture mainly consisting of flaxseed oil, flaxseed protein, dietary fibre (including cellulose and flaxseed gum), carbohydrates and secoisolariciresinol diglucoside (SDG). To investigate the effects of expanded flaxseed meal (EFM) intervention on the hypoglycaemic and lipid-lowering functions of rats on a high-fat, high-sugar (HFHS) diet, EFM was fed to six groups (z = 8) of Sprague–Dawley (SD) rats: normal control, HFHS model, positive treatment control, and low-, medium-, and high-dose EFM (5%, 10% and 20% mass fraction EFM, respectively) groups. The results (8 weeks later) were as follows: (1) medium- and high-dose EFM achieved similar inhibitive effects on blood glucose levels compared with positive treatment (5.94±0.32 mmol/L); (2) all EFM doses significantly reduced total cholesterol, triglyceride and low-density lipoprotein cholesterol levels in the blood plasma of SD rats and (3) EFM significantly increased glutathione peroxidase, superoxide dismutase and catalase activities, increased glutathione levels, and reduced the malondialdehyde content in the plasma of SD rats (P < 0.05). Therefore, EFM mitigated the adverse effects produced by HFHS diet on physiological functions, effectively regulated blood glucose and lipid metabolism, enhanced plasma antioxidant capacity and alleviated oxidative stress in SD rats with a certain dose–effect relationship among the EFM dose groups. Hepatic histological morphologies indicated that EFM also improved the size and density of lipid droplets in the liver of the rats and inhibited the onset of fatty liver. These results suggest that EFM is a potentially useful raw material in the development of blood glucose and lipid-lowering food products.

Development and validation of an ultra-high-performance liquid chromatography-tandem mass spectrometry method to determine the bioavailability of warfarin and its major metabolite 7-hydroxy warfarin in rats dosed with oral formulations containing different polymorphic forms.

A simple, sensitive and rapid ultra-high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry method was developed and validated for the quantification of warfarin and 7-hydroxy warfarin in Sprague Dawley (SD) rats. Animals were administered a single dose of warfarin sodium formulations (crystalline and amorphous) at 12 mg/kg via oral gavage and blood was drawn over a 96-h time course. Sample process recoveries, matrix effect and analyte stability were determined. The linearity for warfarin and 7-hydroxy warfarin was from 5 to 2000 ng/mL in blank SD rat plasma. Correlation coefficients (r2 ) for standard calibration curves were >.98 and analytes quantified within ±15% of target at all calibrator concentrations. The average percent accuracy and precision for intra- and inter-day were 93.7%-113.8% and ≤12.1%, respectively, for warfarin and 7-hydroxy warfarin, across the quality control standards (5, 10, 500, 1800 and 2000 ng/mL). Acceptable analytical recovery (>55%) was achieved with process efficiencies >41.5% and matrix effects <139.9% over the analytical range. Both analytes were stable in stock solution, autosampler, benchtop and three cycles of freeze-thaw with percent accuracy ≥90.2% and precision (percent relative standard deviation) ≤14%. The validated method was successfully applied to a pre-clinical bioavailability study of crystalline and amorphous warfarin sodium formulations in SD rats.

Development and Validation of an Analytical Method for Quantitation of Sulfolane in Rat and Mouse Plasma by GC-MS.

Sulfolane is an industrial solvent commonly used for extraction of aromatic hydrocarbons in the oil refining process, as well in the purification of natural gas. Its wide use and high solubility in water has led to contamination of groundwater. The objective of this work was to develop and validate an analytical method to quantitate sulfolane in rodent plasma in support of the National Toxicology Program toxicology and toxicokinetic studies of sulfolane. The method uses extraction of plasma with ethyl acetate and analysis by gas chromatography-mass spectrometry with electron ionization. The method was validated in male Sprague Dawley (SD) rat plasma over the concentration range of 20-100,000 ng/mL. The method was linear (r ≥ 0.99), accurate (mean relative error (RE) ≤ ±5.1%) and precise (relative standard deviation (RSD) ≤ 2.9%). The absolute recovery was ≥74%. The limit of detection was 0.516 ng/mL. Standards as high as ~2.5 mg/mL could be successfully diluted into the calibration range (mean %RE ≤ ±4.5; %RSD ≤ 4.6). Extracted samples were stable for at least 3 days at ambient and refrigerated temperatures, and freeze/thaw stability in matrix was demonstrated after three cycles over 3 days (calculated concentrations within 90.8-102% of Day 0 concentrations). Sulfolane was stable in frozen plasma for at least 75 days at -80°C (calculated concentrations within 93.0-98.1% of Day 0 concentrations). Matrix evaluation was performed for sulfolane in female SD rat plasma and male and female B6C3F1 mouse plasma (mean %RE ≤ ±4.9; %RSD ≤ 3.3). These data demonstrate that the method is suitable for determination of sulfolane in rodent plasma.

Simultaneous determination of tandospirone and its active metabolite, 1-[2-pyrimidyl]-piperazine in rat plasma by LC-MS/MS and its application to a pharmacokinetic study.

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometry method for the detection of tandospirone (TDS) and its active metabolite 1-[2-pyrimidyl]-piperazine (1-PP) in Sprague-Dawley rat plasma is described. It was employed in a pharmacokinetic study. These analytes and the internal standards were extracted from plasma using protein precipitation with acetonitrile, then separated on a CAPCELL PAK ADME C18 column using a mobile phase of acetonitrile and 5 mm ammonium formate acidified with formic acid (0.1%, v/v) at a total flow rate of 0.4 mL/min. The detection was performed with a tandem mass spectrometer equipped with an electrospray ionization source. The method was validated to quantify the concentration ranges of 1.000-500.0 ng/mL for TDS and 10.00-500.0 ng/mL for 1-PP. Total time for each chromatograph was 3.0 min. The intra-day precision was between 1.42 and 6.69% and the accuracy ranged from 95.74 to 110.18% for all analytes. Inter-day precision and accuracy ranged from 2.47 to 6.02% and from 98.37 to 105.62%, respectively. The lower limits of quantification were 1.000 ng/mL for TDS and 10.00 ng/mL for 1-PP. This method provided a fast, sensitive and selective analytical tool for quantification of tandospirone and its metabolite 1-PP in plasma necessary for the pharmacokinetic investigation.

Simultaneous determination of curcumin, tetrahydrocurcumin, quercetin, and paeoniflorin by UHPLC-MS/MS in rat plasma and its application to a pharmacokinetic study

Curcumin (CUR) is a bioactive compound present in many composite prescriptions of traditional Chinese medicine together with quercetin (QR) and paeoniflorin (PF). Little is known about the influence of QR and PF on the absorption and metabolism of CUR when the three compounds are orally co-administered. In this study, a rapid, sensitive, and reliable ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for the simultaneous determination of CUR, tetrahydrocurcumin (THC), QR, and PF in rat plasma by using tinidazole as the internal standard (IS). A liquid-liquid extraction method with ethyl acetate was used to pre-treat the plasma samples. Chromatographic separation was conducted on a C18 column with isocratic elution using acetonitrile and 0.1% formic acid water solution (80:20, v/v) as the mobile phase at the flow rate of 0.3 mL/min. A TSQ Quantum Access Max API mass spectrometer equipped with electrospray ionisation (ESI) source in selection reaction monitoring (SRM) mode was employed to determine transitions of m/z 369.0 → 176.9, 373.1 → 137.0, 303.0 → 228.9, 478.9 → 120.9, 248.1 → 121.0 for CUR, THC, QR, PF, and IS, respectively. The selectivity, precision, accuracy, extraction recovery, matrix effect, and stability of the method were validated. This developed and validated method was successfully applied in the pharmacokinetic study of CUR, THC, QR, and PF in rats. The effects of QR and PF on the pharmacokinetics of CUR and its metabolite, THC, were evaluated in the plasma of Sprague-Dawley rats that were orally co-administered CUR, QR, and PF. The results showed that the combined use of QR, PF, and CUR has a possible influence on the metabolism and excretion of CUR. Our work provides a fundamental method for the rapid simultaneous determination of CUR, THC, QR, and PF in rat plasma. Furthermore, this study will provide a basic method for the analysis of pharmacokinetic interaction of CUR, QR, and PF and offer a scientific basis for a possible combination therapy with the three compounds.

Analytical performance of a commercial multiplex Luminex-based cytokine panel in the rat

IntroductionMultiplex immunoassays are an important tool in biomarker research during preclinical drug development. However, information regarding analytical performance of commercial multiplex assays for animal species is often limited. To be able to correctly interpret study results, a fit-for-purpose validation approach is recommended. The objective of our study was to provide a realistic example of what level of validation can be expected from this type of assay, using a rat cytokine panel. MethodsThe analytical performance of a commercial Luminex-based multiplex assay comprising IFN-γ, IL-6, IL-10, IL-12p70, IP-10 and TNF-α was evaluated in Sprague-Dawley rat plasma and serum. Calibration curve, working range, precision, accuracy, selectivity, parallelism, dilutional linearity, prozone effect and sample stability were assessed. ResultsAnalytical performance in plasma and serum was comparable. Precision and accuracy results for all analytes were acceptable with coefficient of variation (CV) and relative error (RE) often below 15%, except for serum IL-6. Selectivity results varied per analyte with several cytokines showing CV>30% and no single minimum required dilution (MRD) could be identified. In addition, some striking differences between recombinant and endogenous protein results were observed. A pronounced prozone effect was detected for IP-10. Analytes in samples stored at −70°C were stable (RE<30%) from 1 up to 6months depending on the analyte. DiscussionThe results illustrate the challenges encountered during validation of commercial animal Luminex-based multiplex assays, revealing analytical limitations such as matrix and prozone effects. The Milliplex rat cytokine panel under investigation was deemed suitable for relative quantification of exploratory type biomarkers.

Combined Antihypertensive Effect of Paeoniflorin Enriched Extract and Metoprolol in Spontaneously Hypertensive Rats.

Background:Hypertension is a great global health challenge and it mostly requires drug combination therapy with the various advantages. Metoprolol (MP) and paeoniflorin are both commonly used for the treatment of hypertension. However, whether they exert synergistic effects on antihypertension or not remains unclear, especially on vascular endothelial function.Objective:The purpose of the study is to investigate the advantages of the combined antihypertensive effects of paeoniflorin enriched extract from Radix Paeoniae Alba (RE) and MP in spontaneously hypertensive rats (SHR).Materials and Methods:SHR divided into six groups (n = 8 each group), animals in each group were administrated orally with distilled water, MP (6 and 20 mg/kg), RE (30 and 90 mg/kg), and MP (6 mg/kg) combined with RE (30 mg/kg) (MP + RE), respectively, daily for 6 weeks. Blood pressure (BP) and microcirculation were assessed. The organ bath experiment and hematoxylin and eosin staining were, respectively, performed for the functional and pathological vascular function analysis. Immunohistochemistry was applied to detect endothelial nitric oxide synthase (eNOS) expression in aorta, heart, and kidney. Further, high-performance liquid chromatography was employed to quantitatively determine paeoniflorin in RE and MP + RE sample solvent, as well as in plasma of Sprague-Dawley rats (SD) after single-dose administration of them.Results:The results showed that MP + RE significantly reduced BP, increased microcirculation, improved vascular function and pathological changes, and upregulated eNOS expression. MP was also found to increase the blood concentration of paeoniflorin in SD.Conclusion:The combination of RE and MP could be used for the treatment of hypertension and could improve microcirculation, upregulate eNOS expression, and mitigate endothelial dysfunction in SHR.SUMMARY Paeoniflorin enriched extract from Radix Paeoniae Alba and metoprolol exert synergistic antihypertensive effects. Abbreviations used: RE: Paeoniflorin enriched extract from Radix Paeoniae Alba, MP: Metoprolol, MP + RE: MP combined with RE, NC: Normal control, MC: Model control, SHR: Spontaneously hypertensive rats, SD: Sprague-Dawley rats, H and E: Hematoxylin and eosin, BP: Blood pressure, SBP: Systolic blood pressure, DBP: Diastolic blood pressure, MBP: Mean arterial blood pressure, NA: Norepinephrine, ACh: Acetylcholine, SNP: Nitroprusside, NO: Nitric oxide, eNOS: Endothelial nitric oxide synthase, RPA: Radices Paeoniae Alba, IHC: Immunohistochemistry, Cmax: Peak concentration, Tmax: The time to reach Cmax, t½: Half-life, AUC0-t: Area under the curve of 0-t time; MRT0-t: Mean residence of 0-t time; CL: Clearance rate.

Determination of Tangeretin in Rat Plasma: Assessment of Its Clearance and Absolute Oral Bioavailability.

Tangeretin (TAN) is a dietary polymethoxylated flavone that possesses a broad scope of pharmacological activities. A simple high-performance liquid chromatography (HPLC) method was developed and validated in this study to quantify TAN in plasma of Sprague-Dawley rats. The lower limit of quantification (LLOQ) was 15 ng/mL; the intra- and inter-day assay variations expressed in the form of relative standard deviation (RSD) were all less than 10%; and the assay accuracy was within 100 ± 15%. Subsequently, pharmacokinetic profiles of TAN were explored and established. Upon single intravenous administration (10 mg/kg), TAN had rapid clearance (Cl = 94.1 ± 20.2 mL/min/kg) and moderate terminal elimination half-life (t1/2 λz = 166 ± 42 min). When TAN was given as a suspension (50 mg/kg), poor but erratic absolute oral bioavailability (mean value < 3.05%) was observed; however, when TAN was given in a solution prepared with randomly methylated-β-cyclodextrin (50 mg/kg), its plasma exposure was at least doubled (mean bioavailability: 6.02%). It was obvious that aqueous solubility hindered the oral absorption of TAN and acted as a barrier to its oral bioavailability. This study will facilitate further investigations on the medicinal potentials of TAN.

Preanalytic processing of rat plasma influences thrombin generation and fibrinolysis assays.

Thrombin generation assays (TGA) have potential applications as measures of hemostatic balance in animal models. However, variations in plasma processing greatly influence human TGA, and may also impact on the translational value of TGA in animal studies. The purpose of the study was to compare the performance characteristics of Sprague-Dawley rat plasma prepared by single vs double centrifugation protocols in TGA and fibrinolysis assays. Platelet-poor plasma (PPP) from adult rats (n = 20 males; 20 females) was prepared by centrifugation at 1200g × 12 min, or 2 sequential centrifugations of 2500g × 15 min. Plasma aliquots were assayed fresh and after freeze-thaw in a commercial fluorogenic TGA (Technothrombin TGA, Technoclone) using 2 different trigger reagents containing approximately 7 pM human tissue factor. In addition to TGA variables (lag time, peak thrombin, endogenous thrombin potential), we compared clotting time test and fibrinogen concentration, residual platelet and platelet-derived microparticle (PMP) counts measured by flow cytometry, and variables of fibrin clot formation and lysis measured in turbidimetric assays. Single-centrifugation PPP demonstrated significantly greater thrombin-generating potential regardless of trigger reagent, yielded higher residual platelet and procoagulant PMP counts, and more stable fibrin clot profiles. The influence of a freeze-thaw cycle on TGA varied depending on trigger reagent, and male sex was associated with an overall "procoagulant" phenotype. Preanalytic processing and sex have significant effects on many functional measures of hemostasis in rats. A standardized double centrifugation protocol to prepare PPP is recommended for future studies.

Determination of cepharanthine in rat plasma by LC–MS/MS and its application to a pharmacokinetic study

Context: Cepharanthine (CPA) has been reported to possess a wide range of pharmacological activities. Objective: This study investigates the pharmacokinetic characteristics after oral or intravenous administration of CPA by using a sensitive and rapid LC–MS/MS method. Materials and methods: A sensitive and rapid LC–MS/MS method was developed for the determination of CPA in Sprague–Dawley rat plasma. Twelve rats were equally randomized into two groups, including the intravenous group (1 mg/kg) and the oral group (10 mg/kg). Blood samples (250 μL) were collected at designated time points and determined using this method. The pharmacokinetic parameters were calculated. Results: The calibration curve was linear within the range of 0.1–200 ng/mL (r = 0.999) with the lower limit of quantification at 0.1 ng/mL. After 1 mg/kg intravenous injection, the concentration of CPA reached a maximum of 153.17 ± 16.18 ng/mL and the t 1/2 was 6.76 ± 1.21 h. After oral administration of 10 mg/kg of CPA, CPA was not readily absorbed and reached Cmax 46.89 ± 5.25 ng/mL at approximately 2.67 h. The t 1/2 was 11.02 ± 1.32 h. The absolute bioavailability of CPA by oral route was 5.65 ± 0.35%, and the bioavailability was poor. Discussion and conclusions: The results indicate that the bioavailability of CPA was poor in rats, and further research should be conducted to investigate the reason for its poor bioavailability and address this problem.

The ultra-performance liquid chromatography tandem mass spectrometry method for detection and quantification of C4NP in rat plasma and its application to pharmacokinetic studies.

Combretastatins, which are excellent anticancer agents, are isolated from Combretum. A sensitive ultra-performance liquid chromatography tandem mass spectrometry method was developed and validated for the pharmacokinetic study of a combretastatin analog (C4NP) in rats. Sample pretreatment was finished by simple protein precipitation in which methanol was added to plasma containing an internal standard (buspirone hydrochloride). Liquid chromatograph separation was accomplished on a reverse-phase Kinetex XB-C18 column [50×4.6 mm; internal diameter: 2.6 μm (Phenomenex, Torrance, CA, U.S.A.)] with a gradient mobile phase of acetonitrile (0.05% formic acid, volume for volume) and water (0.05% formic acid) at a flow rate of 0.3 mL/min. The analytes were analyzed in the positive ion by electrospray ionization and quantified in the selective reaction monitoring mode. The entire procedure was validated following the U.S. Food and Drug Administration guidelines for bioanalytical methods validation. Our study investigated, for the first time, the detection and pharmacokinetic characteristics of C4NP in Sprague-Dawley rat plasma. The pharmacokinetic results suggest that C4NP is predominantly restricted to blood or extracellular fluid and is not extensively distributed to most organ tissues. In addition, C4NP can be cleared by renal filtration and active tubular secretion in Sprague-Dawley rats. Toxicokinetics of C4NP in these rats indicate that no saturation of the metabolic or excretion process occurs for C4NP, and metabolic induction and accumulation of toxic injury from multiple dosing are both absent. For 100 μL of analyte, recovery plus high accuracy and reproducibility indicate that our new ultra-performance liquid chromatography tandem mass spectrometry method is a reliable and high-throughput analytical tool for the pharmacokinetic study of C4NP in rats. Those results should be useful for risk assessment.