Influence of experimentally induced fever on the disposition of cefpirome in buffalo calves

The influence of Escherichia coli endotoxin-induced fever on the disposition of cefpirome was investigated in five male buffalo calves following a single intravenous dose of 10 mg kg⁻¹. Blood samples were collected from 1 min to 24 h of drug administration. The drug concentration in plasma was estimated by microbiological assay using E. coli as a test organism. The disposition of cefpirome followed two-compartment open model and the drug was detected above the minimum inhibitory concentration in plasma up to 12 h. The Vd_area and AUC were 0.75 ± 0.01 L kg⁻¹ and 35.1 ± 0.46 μg ml⁻¹ h, respectively. The elimination half-life of 1.81 ± 0.009 h and Cl_B of 0.29 ± 0.004 L kg⁻¹ h⁻¹ reflected rapid elimination and body clearance of cefpirome in febrile buffalo calves. Based on the results, a satisfactory dosage regimen of cefpirome in febrile buffalo calves was calculated to be 6 mg kg⁻¹ to be repeated at 8 h intervals.     

The effects of sulfur mustard exposure and freezing on transdermal penetration of tritiated water through ex vivo pig skin

The percutaneous absorption of tritiated water (³H₂O) through sulfur mustard (SM) exposed abdominal pig skin was measured using in vitro Franz-type static diffusion cells. The barrier function to water permeation following exposure to liquid SM for 8 min and excision 3 h later did not change significantly. A small, but statistically significant difference (P < 0.05) in steady state penetration (Jss), permeability coefficient (Kp) and lag time (t_L) of ³H₂O was observed between fresh skin and skin stored frozen (?20 °C) for up to two weeks. Steady-state penetration and Kp values were significantly higher (P < 0.05) in skin stored frozen compared with fresh skin. Fresh naïve skin had an average Kp of 1.65 × 10^?3 cm h^?1, whereas frozen naïve skin was 2.04 × 10^?3 cm h^?1. Fresh SM exposed skin had a mean Kp of 1.72 × 10^?3 cm h^?1, whereas frozen SM exposed skin was 2.31 × 10^?3 cm h^?1. Lag times were also shorter (P < 0.05) in skin that had been stored frozen. Frozen, SM-exposed porcine abdominal skin may be used for in vitro penetration studies, but effects of treatment and storage on the barrier layer should be taken into account.     

In Vitro Regioselective Stability of β‐1‐O‐ and 2‐O‐Acyl Glucuronides of Naproxen and Their Covalent Binding to Human Serum Albumin

β‐1‐O‐ (NAG) and 2‐O‐glucuronides (2‐isomer) of (S)‐naproxen (NA) were prepared to determine which positional isomer‐(s) of the acyl glucuronide of NA is responsible for forming covalent adducts with human serum albumin (HSA). Their comparative stability and covalent binding adduct formation with HSA were investigated at pH 7.4 and at 37 °C. NA and its acyl glucuronides were simultaneously determined by HPLC. Three positional isomers were formed successively after incubation of NAG in the buffer only. However, when NAG was incubated with HSA (30 mg/mL), isomers other than the 2‐isomer were formed in little or negligible quantities. In HSA solution, NAG (k_d = 2.08 ± 0.08 h⁻¹) was four times less stable than 2‐isomer (k_d = 0.51 ± 0.02 h⁻¹). NAG was degraded by hydrolysis (k_hyd = 1.01 ± 0.10 h⁻¹) and isomerization (k_iso = 1.07 ± 0.07 h⁻¹) to the same extent; however, hydrolysis was predominant for the 2‐isomer (k_d = 0.51 ± 0.02 h⁻¹). The incubation of both NAG and 2‐isomer with HSA led to the formation of a covalent adduct; however, the adduct formation from the 2‐isomer proceeded more slowly than that from NAG. The present results suggest that the covalent binding of NA to HSA via its acyl glucuronides proceeds through both transacylation (direct nucleophilic displacement) and glycation mechanisms; NAG rapidly forms an adduct that may be unstable, and the protein adduct from the 2‐O‐acyl glucuronide is as important for the covalent binding as those from the 1‐O‐acyl glucuronides.     

Covalent inhibition of recombinant human carboxylesterase 1 and 2 and monoacylglycerol lipase by the carbamates JZL184 and URB597

Carboxylesterase type 1 (CES1) and CES2 are serine hydrolases located in the liver and small intestine. CES1 and CES2 actively participate in the metabolism of several pharmaceuticals. Recently, carbamate compounds were developed to inhibit members of the serine hydrolase family via covalent modification of the active site serine. URB597 and JZL184 inhibit fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), respectively; however, carboxylesterases in liver have been identified as a major off-target. We report the kinetic rate constants for inhibition of human recombinant CES1 and CES2 by URB597 and JZL184. Bimolecular rate constants (k_inact/K_i) for inhibition of CES1 by JZL184 and URB597 were similar [3.9 (±0.2) × 10³ M^?1 s^?1 and 4.5 (±1.3) × 10³ M^?1 s^?1, respectively]. However, k_inact/K_i for inhibition of CES2 by JZL184 and URB597 were significantly different [2.3 (±1.3) × 10² M^?1 s^?1 and 3.9 (±1.0) × 10³ M^?1 s^?1, respectively]. Rates of inhibition of CES1 and CES2 by URB597 were similar; however, CES1 and MAGL were more potently inhibited by JZL184 than CES2. We also determined kinetic constants for spontaneous reactivation of CES1 carbamoylated by either JZL184 or URB597 and CES1 diethylphosphorylated by paraoxon. The reactivation rate was significantly slower (4.5×) for CES1 inhibited by JZL184 than CES1 inhibited by URB597. Half-life of reactivation for CES1 carbamoylated by JZL184 was 49 ± 15 h, which is faster than carboxylesterase turnover in HepG2 cells. Together, the results define the kinetics of inhibition for a class of drugs that target hydrolytic enzymes involved in drug and lipid metabolism.     

Determination of orbifloxacin in sheep plasma by high performance liquid chromatography with ultraviolet detection after intravenous and intramuscular administration

IntroductionSingle-dose pharmacokinetics of orbifloxacin (2.5 mg/kg body weight) were determined in clinically normal female Patanwadi sheep (n = 6) following intravenous and intramuscular administration.MethodsOrbifloxacin concentrations were determined by high performance liquid chromatography with ultraviolet detection. The concentration–time data were analyzed by non-compartmental kinetic method.Results and discussionFollowing a single intravenous injection, an elimination half-life (t_1/2β) of 8.31 ± 0.102 h. Steady-state volume of distribution (Vd_ss) and total body clearance (Cl_B) were 3.09 ± 0.282 L/kg and 0.158 ± 0.006 L/kg/h, respectively. Following intramuscular administration, an elimination rate constant (β), the area under the curve from zero to infinity (AUC_0 ? ∞) and the mean absorption time (MAT) were 0.015 ± 0.001 h^? 1, 23.49 ± 1.722 μg·h/mL and 7.50 ± 0.58 h, respectively. The peak plasma concentration (C_max) of 1.81 ± 0.005 µg/mL was achieved at 1.00 ± 0.00 h. The mean residence time (MRT) was 26.25 ± 1.083 h and the absolute bioavailability was 150.8 ± 12.35%, respectively. Orbifloxacin could be useful for the treatment of bacterial infections in sheep that are sensitive to this drug.     

Comparison of average,scaled average,and population bioequivalence methods for assessment of highly variable drugs: An experience with doxifluridine in beagle dogs

Several strategies for overcoming the challenge of establishing bioequivalence (BE) for highly variable drugs (HVDs; drugs having within-subject variability >0.3) have been considered in recent years. Within-subject variability of the area under the curve (AUC_4 h) and peak concentration (C_max) of doxifluridine in the minimal group (n = 24) were 0.444 and 0.491, respectively, meeting the criteria for an HVD. For the large group (n = 60), within-subject variability of the AUC_4 h and C_max were 0.431 and 0.493, respectively. The 90% confidence interval for the AUC_4 h and C_max of the ratio of the test drug to the reference drug exceeded the acceptable BE limits (0.80–1.25) of the ABE (average bioequivalence), in both the minimal and large groups. However, the 90% CI fell within the extended BE limits (0.61–1.64) of the SABE (scaled average bioequivalence), calculated using within-subject variability. The 95% CI of the AUC_4 h and C_max of the ratio of test to reference drug were within the extended BE limit (<1.73) of the PBE (population bioequivalence), calculated using total variance. Our results suggest that the SABE method may be useful for evaluating the BE of HVDs and for meeting the need for international guidelines for BE.     

Upgrading bio-oil produced from the catalytic pyrolysis of sugarcane (Saccharum officinarum L) straw using calcined dolomite

In this study, the catalytic pyrolysis of sugarcane straw (SCS) into bio-oil and chemicals using calcined dolomite was applied for upgraded bio-oil production. Experiments were performed in a custom-built SS316 tube reactor, and the effects of the pyrolysis parameters, including the different dolomite calcination conditions, temperature (400-600 °C), biomass feed rate (0.3–1.2 kg h^?1), sweeping gas flow rate (80–200 cm³ min^?1) and average size distribution (250–1000 µm), were systematically investigated. The results showed that the SCS catalytic pyrolysis process obtained liquid yields of 36.15 wt%, gas yields of 52.09 wt% and solid yields of 11.76 wt% when using a pyrolysis temperature, biomass feed rate, nitrogen sweep gas, and average biomass size of 450 °C, 0.6 kg h^?1, 80 cm³ min^?1 and 500 µm, respectively, with 10 wt% calcined dolomite. The calcined dolomite influenced the bio-oil components from the carbonylation and the cracking of volatile vapor and resulted in an upgraded bio-oil with a lower oxygen content, higher gross calorific value and decreased acid corrosion.     

Sustainable succinic acid production from rice husks

In this study, an investigation was carried out into the production of succinic acid by Actinobacillus succinogenes using the residual biomass rice husks as a sustainable carbon source. The rice husks were submitted to acid hydrolysis in autoclave and in a pressurized polytetrafluorethylene vessel. The hydrolysis conditions were optimized with the aid of a factorial design. The best results were obtained with a pressurized reactor using HCl 2.2% (v v^?1), at a temperature of 174 °C (59 bar), 46 min reaction time, and producing 19.0 g L^?1 glucose and 3.01 g L^?1 xylose. The hydrolysate was detoxified through a combination of pH regulation and adsorption on active carbon; it was subsequently, fermented in anaerobic medium at 37 °C; the nutrient concentration and the agitation speed were also optimized by factorial design. After 54 h static fermentation of the rice husks hydrolysate, supplemented with 8.40 g L^?1 yeast extract and 1.40 g L^?1 NaHCO₃, an amount of 12.5 g succinic acid L^?1 was produced, which corresponds to a yield of 59.9%. This confirms that, rice husks can definitely be used as substrate to produce succinic acid and other priority chemicals     

Preparation of estradiol chitosan nanoparticles for improving nasal absorption and brain targeting

The estradiol(E₂)-loaded chitosan nanoparticles (CS-NPs) were prepared by ionic gelation of chitosan with tripolyphosphate anions (TPP). The CS-NPs had a mean size of (269.3 ± 31.6) nm, a zeta potential of +25.4 mV, and loading capacity of E₂ CS-NPs suspension was 1.9 mg ml⁻¹, entrapment efficiency was 64.7% on average. Subsequently, this paper investigated the levels of E₂ in blood and the cerebrospinal fluid (CSF) in rats following intranasal administration of E₂ CS-NPs. E₂-loaded CS-NPs were administered to male Wister rats either intranasally or intravenously at the dose of 0.48 mg kg⁻¹. The plasma levels achieved following intranasal administration (32.7 ± 10.1 ng ml⁻¹; t_max 28 ± 4.5 min) were significantly lower than those after intravenous administration (151.4 ± 28.2 ng ml⁻¹), while CSF concentrations achieved after intranasal administration (76.4 ± 14.0 ng ml⁻¹; t_max 28 ± 17.9 min) were significantly higher than those after intravenous administration (29.5 ± 7.4 ng ml⁻¹ t_max 60 min). The drug targeting index (DTI) of nasal route was 3.2, percent of drug targeting (DTP%) was 68.4%. These results showed that the E₂ must be directly transported from the nasal cavity into the CSF in rats. Finally, compared with E₂ inclusion complex, CS-NPs improved significantly E₂ being transported into central nervous system (CNS).     

Using transdermal iontophoresis to increase granisetron delivery across skin in vitro and in vivo: Effect of experimental conditions and a comparison with other enhancement strategies

The objectives of the study were (i) to investigate the effect of experimental parameters on the iontophoretic transport of granisetron, (ii) to identify the relative contributions of electromigration (EM) and electroosmosis (EO), (iii) to determine the feasibility of delivering therapeutic amounts of drug for the treatment of chemotherapy-induced nausea and vomiting and (iv) to test the in vitro results in a simple animal model in vivo. Preliminary in vitro studies using aqueous granisetron formulations investigating the effect of drug concentration (5, 10, 20 and 40 mM) and current density (0.1, 0.2, 0.3 mA cm^?2) were performed using porcine ear skin. As expected, cumulative delivery in vitro at the 20 and 40 mM concentrations was significantly greater than that at 5 and 10 mM, which were not statistically different (p < 0.05). Increasing the applied current density from 0.1 to 0.3 mA cm^?2 resulted in a ～4.2-fold increase in iontophoretic flux. Furthermore, in the absence of Na⁺ in the formulation, no dependence of iontophoretic flux on drug concentration was reported (at a granisetron concentration of 40 mM, the transport rate was 2.93 ± 0.62 μg cm^?2 min^?1). Co-iontophoresis of acetaminophen was used to show that EM was the predominant transport mechanism accounting for 71–86% of total granisetron delivery. In vivo studies in Wistar rats (40 mM granisetron; application of 0.3 mA cm^?2 for 5 h with Ag/AgCl electrodes and salt bridges) showed an average iontophoretic input rate (k_input) of 0.83 ± 0.26 μg min^?1 and a maximum plasma concentration (C_max) of 0.092 ± 0.004 μg ml^?1. Based on these results and given the known pharmacokinetics, transdermal iontophoresis could achieve therapeutic drug levels for the management of chemotherapy-induced emesis using a reasonably sized (4–6 cm²) patch.     

Down-regulation of carboxylesterases 1 and 2 plays an important role in prodrug metabolism in immunological liver injury rats

Liver plays a central role in xenobiotics metabolism, thus affecting the in vivo disposition and therapeutic effects of drugs. Carboxylesterases (CESs), with the main isoforms CES1 and CES2, are important in the metabolism of ester-type prodrugs. However, influences of immunological liver injury on the activity of CES remain undefined. In the present study, we demonstrated treatment with lipopolysaccharide (LPS) suppressed the activities of CES1 and CES2. The decreased activities of CES1 and CES2 were preliminarily assessed by the hydrolysis assay for their common substrate p-nitrophenyl acetate (PNPA) with rat hepatic microsomal enzyme. Subsequently, RT-PCR results showed that the levels of CES1 mRNA and mRNA of CES2 (AB010635) and CES2 (AY034877) in the model group were significantly lower than those of the normal control group (P < 0.05). Western blot results showed that the expressions of CES1 and CES2 proteins were decreased (P < 0.05). To further clarify the effects of LPS on the metabolic activities of CESs, pharmacokinetic studies were performed in rats by utilizing imidapril and irinotecan (CPT-11) as the specific substrates for CES1 and CES2, respectively. After treatment with LPS, AUC_0 -∞ and C_max of imidaprilat were decreased from 2084.86 ± 340.66 ng · h^− 1 · mL^− 1 and 234.66 ± 68.85 ng · mL^− 1 to 983.87 ± 315.34 ng · h^− 1 · mL^− 1 and 113.1 ± 19.69 ng · mL^− 1 (P < 0.05), respectively. Moreover, AUC_0 -∞ and C_max of SN-38 were decreased from 8100 ± 918.6 ng · h^− 1 · mL^− 1 and 144.67 ± 20.28 ng · mL^− 1 to 3270 ± 500.5 ng · h^− 1 · mL^− 1 and 56.19 ± 10.38 ng · mL^− 1 (P < 0.05), respectively. In summary, immunological liver injury remarkably attenuated the expressions and metabolic activities of CES1 and CES2, which may be associated with the regulatory effects of cytokines under inflammation.     

In vitro screening of reversible and time-dependent inhibition on CYP3A by TM208 and TM209 in rat liver microsomes

TM208 and TM209, dithiocarbamate derivatives with potential anti-cancer effects, were evaluated in reversible and time-dependent cytochrome P450 (CYP) 3A inhibition assays in rat liver microsomes using testosterone as probe substrate. Both compounds were found to be weak reversible inhibitors and moderate mechanism-based inhibitors of rat CYP3A. For reversible inhibition on rat CYP3A, the K_i values of competitive inhibition model were 12.10±1.75 and 13.94±1.31 μM, respectively. For time-dependent inhibition, the inactivation constants (K_l) were 31.93±12.64 and 32.91±15.58 μM, respectively, and the maximum inactivation rates (k_inact) were 0.03497±0.0069 and 0.07259±0.0172 min^?1 respectively. These findings would provide useful in vitro information for future in vivo DDI studies on TM208 or TM209.     

Clinical Pharmacokinetics of Paclitaxel Liposome with a New Route of Administration in Human Based on the Analysis with Ultra Performance Liquid Chromatography

We investigated the clinical pharmacokinetics of paclitaxel liposome with a new route of administration, which was intrapleural infusion, in nine advanced nonsmall-cell lung cancer (NSCLC) patients with malignant pleural effusions after a single administration. Paclitaxel concentrations were measured in pleural fluid and plasma using a simple and rapid ultra performance liquid chromatography (UPLC) method following intra-and inter-day validations. In subjects, AUC_0–96h values in pleural fluid and plasma were 17831 ± 6439 μgh/mL and 778 ± 328 μgh/mL, respectively, and T_max values were initial time and 6.67 h after administration and the corresponding C_max values were 558 ± 44 μg/mL and 12.89 ± 6.86 μg/mL, respectively. The T_{1/2 IP}, CL_IP and Vd_IP values in pleural fluid were 76 ± 48 h, 0.005 ± 0.002 L/hm² and 0.53 ± 0.23 L/m², respectively. The T_1/2,_pla, CL_pla, and Vd_pla values in plasma were 68.34 ± 56.74 h, 0.184 ± 0.080 L/hm², and 17.53 ± 16.57 L/m², respectively. However, some paclitaxel concentrations from several patients in plasma could not be detected at some designed time-points. Our results might offer new opportunities to design and determine individually appropriate therapeutic dosage regimens based on a pharmacokinetic profile.     

Pulmonary delivery of pyrazinamide-loaded large porous particles

We have improved the aerodynamic properties of pyrazinamide loaded large porous particles (PZA-LPPs) designed for pulmonary delivery. To overcome the segregation of the different components occurring during the spray drying process and to obtain homogeneous LPPs, spray drying parameters were modified to decrease the drying speed. As a result, good aerodynamic properties for lung delivery were obtained with a fine particle fraction (FPF) of 40.1 ± 1.0%, an alveolar fraction (AF) of 29.6 ± 3.1%, a mass median aerodynamic diameter (MMAD_aer) of 4.1 ± 0.2 μm and a geometric standard deviation (GSD) of 2.16 ± 0.16. Plasma and epithelial lining fluid (ELF) concentrations of pyrazinamide were evaluated after intratracheal insufflation of PZA-LPPs (4.22 mg kg⁻¹) into rats and compared to intravenous administration (iv) of a pyrazinamide solution (5.82 mg kg⁻¹). The in vivo pharmacokinetic evaluation of PZA-LPPs in rats reveals that intratracheal insufflation of PZA-LPPs leads to a rapid absorption in plasma with an absolute bioavailability of 66%. This proves that PZA-LPPs dissolve fast upon deposition and that PZA crosses efficiently the lung barrier to reach the systemic circulation. PZA concentrations were 1.28-fold higher in ELF after intratracheal administration than after iv administration and the ratio of ELF concentrations over plasma concentrations was 2-fold greater. Although these improvements are moderate, lung delivery of PZA appears an interesting alternative to oral delivery of the molecule and should now be tested in an infected animal model to evaluate its efficacy against Mycobacterium tuberculosis.     

Chemical composition,antiproliferative and antioxidant properties of lipid classes in ordinary and dark muscles from chub mackerel (Scomber japonicus)

This study investigated to compare lipid profiles in ordinary and dark muscles from chub mackerel and to examine antiproliferative and antioxidative properties of lipid classes. The average levels of neutral lipids (NL), glycolipids (GL), and phospholipids (PL) in ordinary muscle were 92.32 ± 0.19%, 5.10 ± 0.48%, and 2.58 ± 0.46%; in dark muscle were 96.88 ± 0.15%, 2.59 ± 0.36%, and 0.54 ± 0.29%, respectively. The fatty acid composition indicated that PL had a higher percentage of PUFA (especially 22:6n?3) with lower percentages of SFA and MUFA compared to NL and GL (p < 0.05). The main ion peaks of GL in ordinary and dark muscles showed that monocharged and bischarged molecular ion were presented at m/z 876.9 and 438.8, respectively. In MTT assay, inhibition of AGS and HT-29 cell proliferation was greatest with the 0.5 and 1.0 mg mL^?1 GL treatments. The GL of ordinary muscle with 0.05 mg mL^?1 concentrations markedly decreased the levels of reactive oxygen species (ROS) induced by H₂O₂ compared to the control (p < 0.05). From our results, GL might have antiproliferative and antioxidant properties based on protective effect against the production of intracellular ROS.     

Reduced Renal Clearance of Cefotaxime in Asians with a Low-Frequency Polymorphism of OAT3 (SLC22A8)

Organic anion transporter 3 (OAT3, SLC22A8), a transporter expressed on the basolateral membrane of the proximal tubule, plays a critical role in the renal excretion of organic anions including many therapeutic drugs. The goal of this study was to evaluate the in vivo effects of the OAT3-Ile305Phe variant (rs11568482), present at 3.5% allele frequency in Asians, on drug disposition with a focus on cefotaxime, a cephalosporin antibiotic. In HEK293- Flp-In cells, the OAT3-Ile305Phe variant had a lower maximum cefotaxime transport activity, V_max, [159 ± 3 nmol*(mg protein)^- 1/min (mean ± SD)] compared with the reference OAT3 [305 ± 28 nmol*(mg protein)^? 1/min, (mean ± SD), p < 0.01], whereas the Michaelis-Menten constant values (K_m) did not differ. In healthy volunteers, we found volunteers that were heterozygous for the Ile305Phe variant and had a significantly lower cefotaxime renal clearance (CL_R; mean ± SD: 84.8 ± 32.1 mL/min, n = 5) compared with volunteers that were homozygous for the reference allele (158 ± 44.1 mL/min, n = 10; p = 0.006). Furthermore, the net secretory component of cefotaxime renal clearance (CL_sec) was reduced in volunteers heterozygous for the variant allele [33.3 ± 31.8 mL/min (mean ± SD)] compared with volunteers homozygous for the OAT3 reference allele [97.0 ± 42.2 mL/min (mean ± SD), p = 0.01]. In summary, our study suggests that a low-frequency reduced-function polymorphism of OAT3 associates with reduced cefotaxime CL_R and CL_sec .©2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:3451–3457, 2013     

Intracellular disposition of arabinogalactan and asialofetuin in HepG2 cells

The binding and uptake of arabinogalactan and asialofetuin in HepG2 cells was kinetically characterized using ^I25I-labeled ligands. The number of binding sites (n) and the association constant (K) of arabinogalactan was 1.9 × 10⁵ ± 1.2 × 10⁵ sites/cell and 5.0 × 10⁶ ± 3.9 × 10⁶ M^? 1, respectively, whereas the n and K_a of asialofetuin was 2.7 × 10⁵ ± 1.1 × 10⁵ sites/cell and 1.1 × 10⁷ ± 0.7 × 10⁷ M^? 1, respectively. These results suggest that the binding capacity of HepG2 cells for arabinogalactan is lower than that for asialofetuin. Moreover, the amount of arabinogalactan uptake by HepG2 cells was lower than that of asialofetuin. Thus, asialofetuin was preferentially bound and internalized by hepatoma cells compared to arabinogalactan.     

Toxicological effects of clofibric acid and diclofenac on plasma thyroid hormones of an Indian major carp,Cirrhinus mrigala during short and long-term exposures

In the present investigation, the toxicity of most commonly detected pharmaceuticals in the aquatic environment namely clofibric acid (CA) and diclofenac (DCF) was investigated in an Indian major carp Cirrhinus mrigala. Fingerlings of C. mrigala were exposed to different concentrations (1, 10 and 100 μg L⁻¹) of CA and DCF for a period of 96 h (short term) and 35 days (long term). The toxic effects of CA and DCF on thyroid hormones (THs) such as thyroid stimulating hormone (TSH), thyroxine (T₄) and triiodothyronine (T₃) levels were evaluated. During the short and long-term exposure period TSH level was found to be decreased at all concentrations of CA (except at the end of 14^th day in 1 and 10 μg L^−l and 21^st day in 1 μg L^−l) whereas in DCF exposed fish TSH level was found to be increased when compared to control groups. T₄ level was found to be decreased at 1 and 100 μg L^−l of CA exposure at the end of 96 h. However, T₄ level was decreased at all concentrations of CA and DCF during long-term (35 days) exposure period. Fish exposed to all concentrations of CA and DCF had lower level of T₃ in both the treatments. These results suggest that both CA and DCF drugs induced significant changes (P < 0.01 and P < 0.05) on thyroid hormonal levels of C. mrigala. The alterations of these hormonal levels can be used as potential biomarkers in monitoring of pharmaceutical drugs in aquatic organisms.     

Quantification of biliary excretion and sinusoidal excretion of 5(6)-carboxy-2′,7′-dichlorofluorescein (CDF) in cultured hepatocytes isolated from Sprague Dawley,Wistar and Mrp2-deficient Wistar (TR−) rats

Hepatic efflux of drug candidates is an important issue in pre-clinical drug development. Here we utilise a method which quantifies and distinguishes efflux of drugs at the canalicular and sinusoidal membranes in rat hepatocyte cultures. Bi-phasic kinetics of transport of 5(6)-carboxydichlorofluorescein (CDF) at the canalicular membrane was demonstrated in Sprague Dawley (SD) and Wistar (W) rat hepatocytes. The high affinity component (Km = 3.2 ± 0.8 μM (SD), 9.0 ± 3.1 μM (W)) was attributed to Mrp2-mediated transport, the low affinity component (Km = 192.1 ± 291.5 μM (SD), 69.2 ± 36.2 μM (W)) may be attributed to transport involving a separate Mrp2 binding site. Data from membranes (Hill coefficient (h) = 2.0 ± 0.5) and vesicles (h = 1.6 ± 0.2) expressing Mrp2 and from SD (h = 1.6 ± 0.4) and Wistar (h = 4.0 ± 0.6) hepatocytes suggests transport involves more than one binding site. In TR⁻ hepatocytes, CDF efflux was predominantly over the sinusoidal membrane (Km = 100.7 ± 36.0 μM), consistent with low abcc2 (Mrp2) expression and compensatory increase in abcc3 (Mrp3) expression. This report shows the potential of using this in vitro method to model changes in biliary excretion due to alterations in transporter expression.     

Novel pH-Sensitive Lipid-Polymer Composite Microspheres of 10-Hydroxycamptothecin Exhibiting Colon-Specific Biodistribution and Reduced Systemic Absorption

Novel lipid-polymer composite microspheres (LP-MS) were prepared by combining pH-sensitive polymer Eudragit S100 with solid lipid Compritol 888 ATO for colonic delivery of 10-hydroxycamptothecin (HCPT), and pH-dependent controlled drug release has been achieved. The colon-specific biodistribution and uptake by the mucosal tissue were examined using coumarin-6-marked LP-MS. It is proved that good in vitro-in vivo relationship has been achieved, with more drugs being delivered to colon and a higher drug level was maintained for a long period. Moreover, in vivo bioavailability of LP-MS was evaluated with conventional enteric microspheres (enteric MS) as reference. After administration of LP-MS, systemic absorption of HCPT was greatly reduced, with area under the curve from 0 to 24 h (AUC_0 -24h, 2.186 ± 0.27) being significantly lower than that of enteric MS group (6.352 ± 0.696). In conclusion, the novel pH-sensitive LP-MS has potential for colon-specific drug delivery.