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PubMed1983

Biliary excretion of [14C]temazepam and its metabolites in the rat.

The excretion of temazepam and its N-desmethyl metabolite, oxazepam, and their respective O-conjugates was examined following a single intravenous dose of [14C]temazepam to two groups of bile fistula rats, with and without bile replenishment to the animals via duodenal cannulae. During an 8-hr collection period, the two groups produced virtually identical bile volumes, and there were no significant differences between them in the amount of total radioactivity, free temazepam, or the identified metabolites in the bile, as determined by TLC and liquid scintillation counting. Elimination of the radioactive dose was rapid during 0-8 hr, with a half-life of approximately 1 hr. Approximately 85-90% of the administered radioactivity was recovered in the bile: less than 1% as free temazepam, 3% as oxazepam, and approximately 10% as their O-conjugates.

Animals↗

PubMed1983

Pharmacokinetic profile of intravenous liposomal triamcinolone acetonide in the rabbit.

The pharmacokinetics of triamcinolone [2-14C]acetonide, encapsulated in neutral multilamellar liposomes, and a control preparation of the steroid in a 3:1 solution of polyethylene glycol-water was investigated in the rabbit after single intravenous bolus injections. Blood samples were obtained at various times up to 7 hr postinjection and assayed for the drug by liquid scintillation counting. Blood drug concentration-time data showed biexponential decay and were analyzed by nonlinear, least-squares regression analysis to obtain the initial (time zero) drug concentration [(Cb)0] and the initial (fast, alpha) and terminal (slow, beta) disposition rate constants. From these estimates the central compartment volume (Vc) and the respective half-lives [(t1/2) alpha, (t1/2) beta] of the fast and slow disposition phases were calculated. The total body clearance (CLT) and the apparent distribution volume (Vd) were obtained by nonparametric analysis. Significant differences were observed between the liposome-encapsulated dosage form and the solution of the steroid in beta and Vd beta. While beta for the liposomal form was smaller than that for the solution, the apparent Vd was larger with the liposome-encapsulated drug. There was no difference in the total body clearance of the drug in the two dosage forms. Results of the study suggest that when administered by the intravenous route, liposome-encapsulated drug may exhibit extensive tissue distribution and a prolonged half-life.

Animals↗

PubMed1984

In vitro dehalogenation of para-substituted aromatic halides in rat liver preparations.

The in vitro dehalogenation of a series of para-substituted halobenzenes was studied using HPLC separation followed by scintillation counting or neutron-activation analysis. Microsomal and cytosolic deiodination were established for iodobenzene substrates whose para-substituents were CO2H, CHO, NO2, OH, and C6H5 but not for para-iodobenzonitrile. A nonglutathione cytosolic deiodinase was only indicated with 4-iodobiphenyl as the substrate. In vitro dehalogenation could not be established for 4-bromobiphenyl using neutron-activation analysis.

Animals↗

PubMed1985

Effect of phenobarbital pretreatment on the plasma and urinary levels of (-)-alpha-acetylmethadol and its metabolites.

The effect of phenobarbital (PB), an inducer of the hepatic microsomal enzyme system, on the plasma levels and urinary elimination of (-)-alpha-acetylmethadol 1 and its metabolites have been examined in the rat. [3H]1 was administered to saline control and PB-pretreated rats at doses of 5 mg/kg ip (55 muCi/kg). The concentration of 1 and its metabolites noracetylmethadol 2, dinoracetylmethadol 3, methadol 4, normethadol 5, and N-acetylnormethadol 6 were quantitated in plasma and urine over 48 h by TLC and liquid scintillation counting. PB pretreatment significantly decreased the plasma total radioactivity and the levels of 1 and its five metabolites over the 48-h period investigated. Urinary total radioactivity and elimination of 1 and its five metabolites were also reduced in PB-pretreated rats. The results indicated that PB pretreatment markedly affects the in vivo transformation and elimination of 1 and its metabolites. The decrease in the levels observed for 1 and its metabolites in the plasma and urine can be due either to an increase in the metabolism of 1 via a different pathway than the formation of the biologically active metabolites 2, 3, 4, and 5, or it may be that PB is enhancing the further metabolism of these compounds to more polar water-soluble products which are mainly excreted through the bile.

Animals↗

PubMed1986

Analysis of chlorhexidine sorption in soft contact lenses by catalytic oxidation of [14C]chlorhexidine and by liquid chromatography.

Two methods are described for the analysis of chlorhexidine sorption in soft contact lenses. The first is an isocratic ion-pairing high-performance liquid chromatographic (HPLC) method with UV detection at 220 nm that allows the determination of chlorhexidine, p-chloroaniline, and other chlorhexidine degradation products in ophthalmic solutions. This procedure had a detection limit of 0.1 ng. The second involves the catalytic oxidation of the lens matrix containing [14C]chlorhexidine to [14C]carbon dioxide and water. The label is then trapped as carbon dioxide in a cocktail and is analyzed by liquid scintillation counting. These methods are sensitive, accurate, and reproducible, and can be used independently or in conjunction for the determination of chlorhexidine sorption in soft contact lenses.

Adsorption↗

PubMed1986

Distribution of polyhexyl cyanoacrylate nanoparticles in nude mice bearing human osteosarcoma.

[14C]Polyhexyl cyanoacrylate nanoparticles (PHCA), with diameters between 200 and 300 nm, were injected intravenously into nude mice bearing a human osteosarcoma. The distribution in liver, spleen, lung, heart, kidney, GI tract, gonads, brain, muscle, as well as in serum and transplanted tumor fragments was investigated by liquid scintillation counting. The peak levels in all organs with the exception of tumor and spleen were reached within 24 h. The highest levels were found in the organs of the reticuloendothelial system, liver, spleen, and lungs. The radioactivity in the other organs was found to be low, approximately 2%. In the tumor and the spleen the highest levels of radioactivity were found at approximately 7 d. At this stage the level of radioactivity in the tumor was 40 times higher than that in muscle. However, the amount of isotope detected in the tumor was still generally less than 1% of the injected dose. The concentration of radioactivity in the tumor was found to be quite variable. Higher levels of radioactivity were correlated with a low amount of tumor necrosis indicating the importance of viable tumor tissue for the accumulation of the radiolabel in this particular animal model.

Adult↗

PubMed1987

Physicochemical determinants of drug diffusion across the conjunctiva, sclera, and cornea.

This investigation examined some of the barrier properties of the conjunctival, scleral, and corneal membranes. The diffusion of nadolol, timolol, propranolol, penbutolol, sucrose, and inulin was measured across the isolated corneal and scleral membranes of the rabbit using a two-chamber glass diffusion cell. Drug absorption across the cornea and the conjunctiva was studied in vivo by measuring precorneal drug clearance. The drug samples were analyzed either by HPLC or liquid scintillation counting (LSC). For all the compounds tested, the scleral permeability was significantly higher than the respective corneal permeability. The permeability coefficients of the beta-blockers varied in the following manner: propranolol > penbutolol > timolol > nadolol for the cornea, and penbutolol > propranolol > timolol > nadolol for the sclera. The cornea offered substantially more resistance to inulin, a polar, macromolecular substance, than did the conjunctiva. However, the cornea and conjunctiva offered comparable resistance to the smaller and less polar drug timolol. This information may serve as a basis for optimizing the intraocular delivery of drugs that are poorly absorbed across the cornea due to their physicochemical properties.

Animals↗

PubMed1987

Disposition and availability of 5-fluorouracil prodrug 5'-deoxy-5-fluorouridine after oral administration in rats.

5'-Deoxy-5-fluorouridine (dFUR) is a prodrug of 5-fluorouracil (FU) and requires metabolic activation by enzymes that are abundant in several tumors as well as in some normal tissues. 5'-Deoxy-5-fluorouridine is presently under investigation as an orally administered anticancer drug. This study examines the absorption and disposition of orally administered dFUR and its systemic availability in female Fischer rats. Animals were given an oral dose of unlabeled dFUR solution (500 mg.kg-1) and, 5 min later, an intravenous (i.v.) tracer dose of [6-3H]dFUR over a period of 1 min. The concomitant i.v. dose was given to assess the drug clearance during absorption of the oral dose. The blood concentrations of radiolabeled and unlabeled dFUR and FU were analyzed by high-pressure liquid chromatography and liquid scintillation counting. The clearance of the i.v. tracer dose of [6-3H]dFUR was 18.5 +/- 2.5 mL.kg-1.min-1 (mean +/- SD, n = 5). The oral bioavailability, calculated using the clearance of [6-3H]dFUR and the area under the blood concentration-time curve (AUC) of unlabeled dFUR, was 63.4 +/- 16.9%. Eighty to ninety percent of the absorption was completed by 8 h. The absorption rate of dFUR, analyzed by the Loo-Riegelman method, suggests that drug absorption took place in part by saturable mechanisms. The AUC of FU after the oral dose was 15-35% higher than that after i.v. injections of dFUR at the same dose. Analysis of the FU data indicates that a fraction of the dFUR dose was metabolized to FU during the presystemic first pass.

Absorption↗

PubMed1988

Distribution of polyhexylcyanoacrylate nanoparticles in nude mice over extended times and after repeated injection.

Carbon-14-labeled polyhexylcyanoacrylate nanoparticles, with diameters between 200 and 300 nm, were injected intravenously into nude mice. The distribution in liver, spleen, lung, heart, kidney, GI tract, gonads, brain, muscle, and serum was investigated by liquid scintillation counting. After a single injection, the radiolabel was cleared slowly with 45% remaining after 28 d and 8% remaining after 140 d. After repeated injection with an interval of 28 d (twice or thrice), relatively higher proportions of the dose were found in the spleen and lung as compared with those in other organs. No histological alterations were observed in the liver, spleen, or lung.

Animals↗

PubMed1990

Pharmacokinetics of falipamil after intravenous administration to humans.

Falipamil (2-[3-[3-(3,4-dimethoxyphenetylmethylamino]propyl]-5,6- dimethoxyphthalamidine; 1) is a new specific bradycardic agent for the treatment of sinus tachycardia. Pharmacokinetics of falipamil in humans (n = 6) was determined in plasma and urine after iv administration of 100 mg (1.85 MBq) per person of 14C-labeled drug by liquid scintillation counting and by a specific, sensitive reversed-phase totally automated HPLC system with fluorimetric detection. Recovery of total radioactivity was 91.8 +/- 3.7%, with 68.2 +/- 4.3% in urine and 23.6 +/- 2.5% in the feces. The majority of radioactivity was excreted within 24 to 48 h. The parent drug, falipamil (1), and its N-desmethyl-metabolite (2), which is approximately 100 times less active than 1, contributed 14.1 +/- 1.6 and 4.5 +/- 0.7%, respectively, of the dose to urinary excretion. Plasma protein binding of 1 and 2 was 87.9 +/- 1.2 (concentration range: 2000-8000 ng/mL) and 89.7 +/- 0.5% (concentration range: 62.5-1000 ng/mL), respectively. Plasma concentrations of 1 peaked at 2 min at 724 +/- 173 ng/mL, declined biphasically, and were fitted to a two-compartment open model. Plasma concentrations of 2 were very low, in all cases ranging from 0 to 35 ng/mL. The dominant terminal half-life (beta-phase) of 1 from plasma was 1.8 +/- 0.6 h (range 1.4-2.9 h), mean residence time was 2.4 +/- 0.4 h, total body clearance was 1108.5 +/- 119 mL/min, and renal clearance was 117 +/- 20 mL/min. All parameters demonstrated very low intersubject variability.

Adult↗

PubMed1993

Zatebradine: pharmacokinetics of a novel heart-rate-lowering agent after intravenous infusion and oral administration to healthy subjects.

Zatebradine (1; UL-FS 49 CL; 1,3,4,5-[tetrahydro-7,8-dimethoxy-3-[3-[ [2-(3,4-dimethoxyphenyl)ethyl]methylamino]propyl]-2H-3-benzazepin- 2-on- hydrochloride) is the proposed INN name for a nonchiral, novel, specific heart-rate-lowering drug that is suitable for the treatment of stable angina pectoris. The pharmacokinetics of 1 and of total radioactivity in healthy volunteers (n = 6) were determined after intravenous infusion and oral administration of an experimental drug solution containing 7.5 mg (1.85 MBq) of 14C-labeled drug. Concentrations in plasma and urine were measured by a specific, sensitive, reversed-phase automated high-performance liquid chromatography system with fluorimetric detection at 285 nm Ex, 315 nm Em and by liquid scintillation counting. Recovery of total radioactivity was 89.8 +/- 2.3% (infusion) and 92.2 +/- 3.0% (oral). Renal elimination of total radioactivity was 62.5 +/- 2.0% (infusion) and 48.8 +/- 3.1% (oral). After intravenous infusion and oral administration, 27.3 +/- 2.4 and 43.4 +/- 3.9%, respectively, of the administered dose was eliminated in the feces. Absorption, based on renal excretion of total radioactivity following oral and intravenous dosing, was 79.2 +/- 15.3% (mean +/- standard deviation). Unchanged parent drug contributed 28.4 +/- 5.8% (infusion) and 12.4 +/- 3.7% (oral) of the dose to renal excretion. Zero to three minutes after cessation of the 20-min infusion, the maximum concentration of parent drug in plasma was 161.9 +/- 70.9 ng/mL. After oral administration, a mean peak concentration in plasma of 24.3 +/- 6.7 ng/mL (0.5-3 h postadministration) was reached. Data regarding levels of 1 in plasma could be adequately fitted with an open, two-compartment model.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1993

Metabolism of 3-indolylacetic acid during percutaneous absorption in human skin.

This study assessed the in vitro percutaneous absorption and metabolism of 3-indolylacetic acid after topical dosing to human skin from four sources. The metabolism of the compound during percutaneous absorption was assessed. The absorbed and metabolized chemicals were analyzed by radioactive scintillation counting and thin-layer chromatography: 1.2% +/- 0.04%, 1.4% +/- 0.07%, 3.0% +/- 1.0%, and 0.1% +/- 0.02% of the applied doses permeated through human skin samples from sources A to D, respectively, whereas 3.4% +/- 0.5% to 20.0% +/- 0.2% of the applied doses were retained by the skin. Of the absorbed dose, 2.1% +/- 1.0% to 12.1% +/- 3.5% was present as metabolites in the receptor fluid, and 2.2% +/- 0.5% to 5.2% +/- 0.1% was present as metabolites retained in the skin. Microsomal fractions were prepared from the skin samples, and the actions of these preparations on 3-indolylacetic acid were estimated. 5'-Hydroxyl-3-indolylacetic acid, 5',6'-dihydroxy-3-indolylacetic acid, and 5,6-dihydroxyindole were formed both during percutaneous absorption and by skin microsomal preparations. In addition, the skin samples biotransformed the acid to metabolic indican (3-indoxylsulfuric acid) and to the glucuronide conjugate of indole. The possible functional significance of the metabolism is discussed.

Administration, Cutaneous↗

PubMed1993

Absorption, bioavailability, and pharmacokinetics of tebufelone in the rat.

Tebufelone (NE-11740) is a member of the new di-tert-butylphenol class of anti-inflammatory agents. It exhibits good inhibitory activity against cyclooxygenase and 5-lipoxygenase in vitro. It also shows excellent anti-inflammatory activity and inhibits bone resorption in vivo in the rat adjuvant arthritis model at an oral dose level of 1 to 2 mg/kg. The absorption, bioavailability, and pharmacokinetics of tebufelone were investigated in male Sprague-Dawley rats. Tebufelone labeled with carbon-14 was administered intravenously at doses of 0.5 and 2 mg/kg and perorally at doses of 2 and 10 mg/kg to fasted rats. Plasma samples taken from the rats at timed intervals were analyzed for total radiolabel by scintillation counting and for tebufelone by a mass spectrometric method. Comparison of the total radiolabel and tebufelone areas under the curves (AUCs) of concentration of tebufelone versus time from the 2-mg/kg intravenous and 2-mg/kg oral doses indicates that tebufelone is completely absorbed and 100% bioavailable at this dose level in the rat. The AUCs are a linear function of dose at the 0.5- and 2-mg/kg dose levels, but the AUC of the 10-mg/kg dose exhibits a nonproportional increase, suggesting saturation of elimination processes at this higher dose.

Absorption↗

PubMed1995

Circulation time and body distribution of 14C-labeled amino-modified polystyrene nanoparticles in mice.

Commercially available amino-modified polystyrene particles of size range 100-1,000 nm were radioactively labeled with [14C]-formaldehyde. A study of the circulation time and body distribution of these particles was carried out in mice. The animals were sacrificed at 1-30 min after intravenous administration of the particles. The blood and organ (liver, spleen, lung) profiles of particles were determined by measuring their radioactivity by means of liquid scintillation counting. In general, larger particles were eliminated from blood faster than smaller particles. The blood elimination half-life ranged from 1.36 to 4.92 min. The particles were mainly taken up by the liver with larger particles being taken up faster than the smaller particles. At 30 min after injection, 60% of the administered 100 nm particles were present in the liver, whereas 85% of the 100 nm particles were found in the liver. Accumulation in the spleen was 1-3% of the total number administered in the entire size range. At 1 min after injection, less than 3% of the total dose administered was present in the lungs and this value decreased rapidly to less than 1% at 2 min. The only exception occurred for 100 nm, where 2.35% was present in the lungs at 2 min after injection.

Animals↗

PubMed2005

Purification of 3-indolylacetic acid by solid phase extraction.

This paper deals with the use of solid-phase extraction (SPE) for the extraction and purification of 3-indolylacetic acid (IAA), the main and most important representative of the plant growth regulators auxins. The procedure is based on the use of C18-SPE columns in two steps. In the first one, raw extract in methanol:water (4:1) is applied on the column in order to remove neutral ballast. In the second step the eluate is diluted with water to a final methanol concentration of 20% (to decrease the elution strength of the solvent) and acidified with formic acid to a final concentration of 1% (to convert the IAA from the anionic to the neutral form). Neutral IAA is then retained on the second SPE column, eluted by (acidified) methanol, and subjected to final analysis. Scintillation counting of tritium labeled IAA standard was used for the investigation and optimization of the SPE procedure. Gas chromatography with mass spectrometric detection was suggested as a convenient method for routine determination of IAA after its methylation with diazomethane. Overall recovery of the procedure was estimated as 89-94% and a physiological level of IAA equal to 0.48 nmol/g (84 ng/g) fresh weight was found using an optimized SPE-GC-MS method.

Chromatography, Liquid↗

PubMed1982

Ara-C cytokinetic studies in normal tissues in vivo.

The importance of including normal tissues in the design of cytokinetic-based chemotherapeutic schedules is becoming increasingly apparent. However, the lack of rapid analytical techniques to obtain quantitative cytokinetic data on target subpopulations in heterogenous normal tissues, such as the gastrointestinal and hematopoietic system, has limited the inclusion of these tissues in therapy design. Once target subpopulations are identified and/or discriminated, flow cytometry in conjunction with radioactivity measurements by liquid scintillation counting can be used to rapidly obtain quantitative cytokinetic data during drug therapy. The present paper reviews our current cytokinetic techniques and the applications and limitations of these techniques in the analysis of Ara-C-induced perturbations in the small intestine and hematopoietic system. Cell cycle information both prior to and 30 hrs following a single Ara-C treatment was obtained in the intestinal crypts and femoral marrow population using radioactive precursor uptake and flow cytometric techniques. In addition, the relationship between crypt cell survival and animal lethality following Ara-C treatment was determined to better understand the impact of a damage to a regenerative population on the "clinical endpoint" of animal survival. Understanding the principles behind the normal tissue toxicity which occurs during multidose treatment will hopefully allow modulation of this toxicity through the rational design of optimal chemotherapeutic schedules.

Animals↗

PubMed1991

Qualitative and quantitative changes in protein synthesis of bovine follicular cells during the preovulatory period.

To understand the mechanisms governing oocyte maturation better, the effects of the gonadotropin surge were studied on follicular cells of bovine preovulatory follicles. For this purpose, qualitative and quantitative changes in protein synthesis by both granulosa cells and cumulus cells were compared relative to the luteinizing hormone (LH) surge and the resumption of meiosis in the oocyte. Follicular cells were collected at different times before and up to 25 hr after the LH surge. For each individual preovulatory follicle, granulosa and cumulus cells were incubated separately for 3 hr with 3H-methionine or with 35S-methionine. Newly synthesized cytosolic proteins from granulosa and cumulus cells and proteins secreted into the medium were analyzed by polyacrylamide gel electrophoresis. The radioactivity was measured by liquid scintillation counting after slicing of the gels or revealed by fluorography. Three major peaks of the newly synthesized proteins, with molecular weights of 76, 56, and 30 kDa, were studied throughout the preovulatory period. After the LH surge, the overall level of protein synthesis increased in granulosa cells. In addition, the pattern of cytosolic proteins in granulosa cells changed, and, in particular, the relative synthesis of the 30 kDa peak decreased. These changes in cytosolic protein synthesis may be due to the action of LH since they could be reproduced in vitro in LH-stimulated granulosa cells. A predominant peak of 56 kDa was secreted by granulosa cells throughout the experimental period. No significant change was observed in proteins synthesized by cumulus cells under the same experimental conditions. The amounts of radioactivity incorporated into the three major proteins secreted by granulosa cells, however, were correlated significantly with the amounts of radioactivity incorporated by similar proteins synthesized by cumulus cells. These results indicate that cumulus cells respond differently from granulosa cells to the gonadotropin surge but not in an independent manner.

Animals↗

PubMed1991

Development of an in vivo 19F magnetic resonance method for measuring oxygen deficiency in tumors.

A 19F magnetic resonance spectroscopy (MRS) approach to measuring hypoxia in experimental tumors in rats at a field strength of 2.35 T has been investigated in a combined study of in situ and excised tumors. The detection of tumor hypoxia is based on the hypoxia marker approach which depends on the selective, covalent binding of a fluorinated 2-nitroimidazole to hypoxic cells. The 19F MRS measurement of in vivo hypoxia marker binding was made at a fixed postinjection time when unbound, circulating marker molecule concentrations had dropped below detectable levels. A correlation between 19F MRS and scintillation counting measures of tumor-bound, tritium-labeled hypoxia marker was observed. There was no correlation between integrated 19F MRS hypoxia marker signals and the in vivo 31P MRS parameters of hypoxia which have been developed to measure normal tissue ischemia. Radiolabeling studies and previous immunohistochemical studies with the fluorinated hypoxia marker support the conclusion that the 19F MRS approach has promise as a physically noninvasive guide to the use of hypoxia-dependent therapies at clinically usable MRS field strengths.

Adenocarcinoma↗