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PubMedDate not supplied

Disposition of intravenous theophylline-7-acetic acid in rabbits.

Theophylline-7-acetic acid (T7AA) was administered intravenously to rabbits so that its distribution and rate of elimination could be ascertained. The analytical techniques used were liquid scintillation counting (14C) and high pressure liquid chromatography. T7AA was eliminated rapidly in the urine; the T 1/2 was 11.6 min. This drug appears to accumulate in the kidney because after 60 min, approximately 15 per cent of the intravenous dose was found in that organ.

Animals↗
PubMedDate not supplied

Intestinal lymphatic absorption of cyclosporin A following oral administration in an olive oil solution in rats.

The intestinal lymphatic absorption of cyclosporin A (CyA) following oral administration of 6.5 +/- 0.6 and 25.2 +/- 1.4 mg kg-1 doses of the drug dissolved in an olive oil solution was studied using a thoracic duct-cannulated rat model. Cumulative lymph samples were collected for up to 114 h post-dosing and assayed by liquid scintillation counting. In this study, the estimated amount of lymphatically absorbed CyA was 0.35 +/- 0.13 and 0.47 +/- 0.29 per cent of the respective doses. In terms of the overall oral bioavailability of CyA (Fpo) by all absorptive mechanisms, the intestinal lymphatics accounted for the absorption of approximately 2 per cent of the total amount of absorbed drug. Fpo was 21.3 +/- 2.5 per cent. The results of this study suggested that lipophilicity alone was not the only factor governing intestinal lymphatic drug absorption. An explanation for the low level of lymphatic CyA absorption is presented. In addition, some reasons for the low overall oral bioavailability of CyA are discussed.

Administration, Oral↗
PubMedDate not supplied

Pharmacokinetics and pharmacodynamics of bromocriptine in the rat.

The absorption, distribution, and excretion of bromocriptine were studied following oral and parenteral administration of non-radioactive and 14C-labelled drug in the rat. Total radioactivity was measured in blood, tissues, and excreta by liquid scintillation counting while the parent drug was determined in plasma and selected tissues by radioimmunoassay. The pharmacokinetic observations were compared with the time course of drug-induced hypothermia in cold-room acclimatized rats. The results indicated that oral doses of bromocriptine were rapidly, though incompletely (32-40 per cent), absorbed, but underwent extensive first-pass metabolism, resulting in an absolute bioavailability of only 6 per cent. The bioavailability increased to approximately 22 per cent in rats pretreated with the hepatic microsome inhibitor proadifen, thus suggesting the liver as the principal site of biotransformation. Absorbed bromocriptine showed preferential distribution into the tissues, although no apparent accumulation of drug-related material occurred in the body. The drug was eliminated almost exclusively by metabolism and biliary excretion into the faeces. Comparison of the pharmacodynamic and the pharmacokinetic profiles indicated a dose relationship between hypothermia and plasma bromocriptine concentrations but not total radioactivity levels. The hypothermic response was also intensified by proadifen pretreatment, thus confirming the parent drug as the pharmacologically active entity. It is believed that the previously reported delay in the onset of bromocriptine activity is not pharmacokinetic in nature, but is related to the properties of the receptors at the target site or to the pharmacologic events that result in the observed effects.

Animals↗
PubMedDate not supplied

Amiodarone pharmacokinetics. II. Disposition kinetics following subchronic administration in rats.

A 30 mg kg-1 intravenous bolus of 14C-amiodarone (19 microCi kg-1) was given to male Sprague-Dawley rats pretreated with 0 (vehicle), 25 or 100 mg kg-1 day-1 of amiodarone HCl orally for 37-42 days to determine the effects of dose and duration of administration on the disposition kinetics of amiodarone. Serial blood samples and total urine were collected over 48 hours and assayed for 14C-amiodarone by liquid scintillation counting following separation by HPLC. In all three groups, the blood 14C-amiodarone concentration-time curves declined bioexponentially with terminal half-lives (t1/2 beta) ranging from 14-22 hours. No differences in beta, t1/2 beta, or central compartment volume (Vc) were observed between the three groups of rats. In the rats pretreated with 100 mg kg-1 day-1 of amiodarone HCl for 5-6 weeks, amiodarone clearance (CL) and steady state volume of distribution (Vss) were reduced 52 per cent (12.2 to 5.9 ml min-1 kg-1) and 41 per cent (11.73 to 6.97 l kg-1), respectively. At the lower amiodarone daily dose, no changes in CL or Vss were observed. Negligible levels of radioactivity were detected in the urine. Amiodarone accounted for approximately 30-40 per cent of the total radioactivity in each blood specimen. This study demonstrated that CL and Vss were dose-dependent, and that beta, t1/2 beta and Vc were dose-independent. The results further suggested that the disposition kinetics of amiodarone were independent of the duration of drug administration.

Amiodarone↗
PubMed1994

Disposition of 14C-dapoxetine in rats: complementary experiments with whole-body autoradiographic and tissue dissection techniques.

Tissue distribution studies, utilizing whole-body autoradiography and organ dissection techniques, were conducted in male Fischer 344 rats following the oral administration of 14C-dapoxetine HCl, a potent serotonin reuptake inhibitor. The preliminary study using whole-body autoradiography proved invaluable in locating radioactivity in an organ not usually harvested in a tissue distribution study, namely the preputial gland. Selected organs, based on whole-body autoradiography findings, were dissected from rats and analyzed for radiocarbon content by liquid scintillation counting and for parent drug and N-dealkylated metabolites by extraction and HPLC analysis. Highest concentrations of radiocarbon were observed in the organs of absorption and elimination (ileum, cecum, stomach, duodenum, liver, colon, and kidney) but notable quantities were observed in the lung and preputial and Harderian glands. Most tissues had returned to background radioactive levels 72 h after dosing but persistent concentrations of radiocarbon were present in the preputial gland and liver one week after the single dose of 14C-dapoxetine. Analysis by HPLC demonstrated the presence of parent drug and N-desmethyl metabolite (nor-dapoxetine) in those organs examined; however, the majority of the radioactivity remained unidentified.

Animals↗
PubMed2001

In vitro protein binding studies with BMS-204352: lack of protein binding displacement interaction in human serum.

BMS-204352, a maxi-K channel opener, is currently under development for the treatment of stroke. Protein binding of BMS-204352 was determined in sera from several species, namely, rat, monkey, dog, and human. Data indicated that the compound was shown to be highly protein bound in serum from all species (ca. 99.6%). In order to test for the potential for drug-drug interactions and competitive displacement of BMS-204352 by diazepam, phenytoin, propranolol, and warfarin, in vitro experiments were performed using spiked human serum and ex vivo human plasma samples. Protein binding was determined using equilibrium dialysis for 4 h at maximal therapeutic concentrations for each drug alone or in appropriate combination in spiked serum samples. Ex vivo samples from a clinical BMS-204352 study (0, 1, and 24 h) were dialyzed separately after addition of diazepam, phenytoin, propranolol, or warfarin. Drug content in biological matrices was measured for radioactivity using liquid scintillation counting. Results indicated that (1) addition of diazepam, phenytoin, propranolol, or warfarin did not alter the free fraction of BMS-204352; (2) BMS-204352 did not displace diazepam, phenytoin, propranolol, or warfarin from their protein binding sites, and (3) comparison of ex vivo plasma samples after BMS-204352 dosing indicated no impact of BMS-204352 and/or its metabolites on the free fraction of diazepam, phenytoin, propranolol, or warfarin. In conclusion, the potential for a drug-drug interaction due to alterations in protein binding with BMS-204352 is unlikely.

Animals↗
PubMed2002

Disposition of radiolabeled BMS-204352 in rats and dogs.

BMS-204352, a maxi-K channel opener, is currently under development for the treatment of stroke. The objective of this study was to determine the pharmacokinetics, mass balance and absolute oral bioavailability of [(14)C]-BMS-204352 in rats and dogs. [(14)C]-BMS-204352 was administered, to rats (n=10/group; parallel design, 6 mg/kg) and dogs (n=4/group; crossover design, 2 mg/kg), as an oral (PO) or as a 3-min intraarterial (IA) infusion in rats and a 6-min intravenous (i.v.) infusion in dogs. Blood, urine, and feces samples were collected and analyzed for unchanged BMS-204352 (plasma) using a validated LC/MS assay and for total radioactivity (plasma, urine, feces) using liquid scintillation counting. The mean total body clearance (CLT) and steady-state volume of distribution (VSS) values for the unchanged BMS-204352 were 2.58 +/- 0.48 l/h/kg and 6.3 +/- 1.14 l/kg, respectively, in rats and 0.21 +/- 0.02 l/h/kg and 4.06 +/- 0.47 l/kg, respectively, in dogs. In both species, the elimination half-life of total radioactivity was significantly longer as compared to the unchanged drug. After IA administration of radiolabeled BMS-204352 to rats, ca. 5.9 and 85% of radioactivity was recovered within 7 days in urine and feces, respectively; corresponding recoveries after PO dosing were 4.5 and 99.5%, respectively. The recoveries were similar in dogs, i.e., ca. 5.2 and 83% of administered radioactivity recovered in urine and feces, respectively, for IV dose and ca. 4 and 86%, respectively, for PO dose. These data indicate that nonrenal (biliary) elimination in both species was predominant. Based on comparable urinary recovery of radioactivity and plasma AUCs of radioactivity, the extent of oral absorption of BMS-204352 appeared to be complete in both species. The absolute oral bioavailability was 55% in rats and 79% in dogs. Bioavailability and extent of absorption data suggest evidence of first pass metabolism of BMS-204352 in the rat and dog.

Administration, Oral↗
PubMed2006

Evidence of a flip-flop phenomenon in acamprosate pharmacokinetics: an in vivo study in rats.

The pharmacokinetics of acamprosate were examined in the rat after oral and intravenous administration in order to detect the possible presence of a flip-flop phenomenon. Rats received 9.3 or 73.3 mg/kg of the drug as an intravenous bolus. The same doses were orally administered via gastric intubation. Plasma samples were taken from the jugular vein for determination of acamprosate concentration by liquid scintillation counting. The drug content was also quantified in urine and faeces. The acamprosate bioavailability was close to 20%, the amount recovered in the faeces being around 80% of the administered dose. The terminal slope of the oral plasma curve was significantly lower than that obtained after intravenous administration of the drug at both doses tested (p<2 x 10(-6) in both cases). Moreover, the downward slope after oral administration (lambda2=0.006 +/- 0.001 min(-1)) practically coincided with the first-order absorption rate constant, previously reported by us, obtained using an in situ rat gut technique. It is concluded that the acamprosate absorption rate is considerably slower than its elimination rate so that the drug exhibits flip-flop pharmacokinetics after oral administration. The lower intrinsic first-order absorption rate constant, ka, is responsible for this phenomenon.

Acamprosate↗
PubMed1994

Sinusoidal 60 Hz electromagnetic fields failed to induce changes in protein synthesis in Escherichia coli.

Escherichia coli JM83 [F- ara delta(lac-proAB) rpsL [phi 80d delta (lacZ)M15]] in midlog growth phase at 30 degrees C were exposed to 60 Hz sinusoidal magnetic field of 3 mT of nonuniform diverging flux, inducing a nonuniform electric field with a maximum intensity of 32 microV/cm using an inductor coil. Exposed and unexposed control cells were maintained at 30.8 +/- 0.1 degrees C and 30.5 +/- 0.1 degrees C, respectively. Quadruplicate samples of exposed and unexposed E. coli cells were simultaneously radiolabeled with 35S-L-methionine at 10 min intervals over 2 hr. Radiochemical incorporation into proteins was analyzed via liquid scintillation counting and by denaturing 12.5% polyacrylamide gel electrophoresis. The results showed that E. coli exposed to a 60 Hz magnetic field of 3 mT exhibited no qualitative or quantitative changes in protein synthesis compared to unexposed cells. Thus small prokaryotic cells (less than 2 microns x 0.5 micron) under constant-temperature conditions do not alter their protein synthesis following exposure to 60 Hz magnetic fields at levels at 3 mT.

Autoradiography↗
PubMed2003

Release kinetics of transforming growth factor-beta1 from fibrin clots.

In any therapeutic model involving a tissue-engineering approach to the repair of partial-thickness articular cartilage defects, a chondrogenic differentiation factor is required to ensure tissue-specific healing. Transforming growth factor-beta1 (TGF-beta1) is known to act in this capacity, but at such high concentrations as to render its direct injection into the joint cavity inadvisable. This situation calls for a delivery system that can be applied directly to the defect site and that will release the drug gradually over a period of some weeks. Liposome encapsulation represents one such system, and has been recently implemented with some success in an animal model for cartilage repair. However, the kinetics of TGF-beta1 release have not been determined, it was the purpose of the present study to characterize these. The liberation of [(125)I]-labeled TGF-beta1 from fibrin matrices containing this agent in either a free or liposome-encapsulated form was monitored by liquid scintillation counting for 25 days in vitro. During the initial 5 days, fibrin clots containing liposome-encapsulated TGF-beta1 released this cytokine at a slower rate (2% to 4% per day) than did those containing the free molecules (10% to 20% per day); thereafter, the release rates were similar. At the end of the incubation period, only 40% of the liposome-encapsulated TGF-beta1 had been released from the fibrin clots, as compared with 68% from those containing the free molecules. Liposome encapsulation thus represents a suitable means of establishing a slow-delivery system in tissue-engineering approaches to articular cartilage repair.

Adsorption↗
PubMed1994

Bacterial translocation during peroperative colonic lavage of the obstructed rat colon.

Peroperative antegrade colonic lavage is often performed before primary anastomosis in emergency colonic surgery. The influence of colonic lavage on bacterial translocation from the obstructed colon was determined. Forty female Wistar rats were studied in four groups: (1) control; (2) non-obstructed with lavage; (3) obstructed; and (4) obstructed with lavage. Ligature obstruction of the rectum was performed in groups 3 and 4. Some 4 days later 35S-radiolabelled Escherichia coli was inoculated into the colon of all animals. Groups 2 and 4 underwent colonic lavage. Lavage in the group 4 animals with left-sided colonic obstruction significantly increased the levels of E. coli in regional nodes, liver, spleen, lung, kidney and blood (as assessed by organ culture and scintillation counting) compared with those in groups 1, 2 and 3 (P < 0.05). These results suggest that peroperative lavage of the obstructed colon significantly increases the level of bacterial translocation.

Anastomosis, Surgical↗
PubMed1979

A microprocessor controlled mass spectrometer for the fully automated purification and isotopic analysis of breath carbon dioxide.

Breath tests that measure the oxidative utilization of 13C labeled substrates have been shown to be clinically useful, but have failed to gain wide acceptance because of the slow and costly isotopic analysis of the breath samples. Therefore we have developed a fully automated, microprocessor controlled CO2 purification and isotopic analysis system. The breath CO2 is cryogenically purified by passage through cold traps of -94 degrees C and -196 degrees to condense water and CO2, respectively. The CO2 is intorduced into a dual inlet, peak-stepping mass spectrometer and analyzed for isotopic content by comparison with a known standard. Thirty samples can be analyzed without operator intervention. Analysis time average 14 minutes per sample, and the analysis has a precision of 0.3% which corresponds to 3 parts excess 13C per 10(6) parts CO2. The speed of analysis is comparable with scintillation counting and permits next day reporting of clinical breath test results. The precision is sufficient for clinical applications as it is less than 0.7% isotopic variation in basal breath CO2.

Breath Tests↗
PubMed1988

Are (13C)cortisol and (3H)cortisol metabolized identically to natural cortisol in adrenalectomized piglets?

Adrenalectomized piglets were intravenously administered a mixture of (13C4)cortisol and (3H)cortisol and natural cortisol to determine if the two tracers are metabolized identically to natural cortisol. Urine was collected after 0.5, 1.0, 1.5 and 2.0 days and the isotope dilution was measured in the four major urinary cortisol metabolites, namely tetrahydrocortisone (THE), tetrahydrocortisol (THF), alpha- and beta-cortolone in the cumulative urines. In contrast to other studies, because of the sensitivity of the method used to measure the 13C4 enrichment, non-cumulative urine collections were also analysed. Quantification of the 13C4 isotope enrichment was carried out by gas chromatography/mass spectrometry with selected ion monitoring. The specific activities of the metabolites from the cumulative urine collections were determined by high-performance liquid chromatography and scintillation counting. Small secondary isotope effects seemed to occur during the metabolism of (13C4)cortisol, as a decrease in isotope enrichment in all four metabolites was measured. These effects were easily observed with alpha- and beta-cortolone isolated from the cumulative urine collections; the enrichment decreased by 19% and 14%, respectively. The lowering in isotope dilution in THE observed in the 2.0 day cumulative urine collection in piglets 1 and 2 were 4% and 3%, respectively. A lowering in isotope dilution in THF in the 2.0 day cumulative urine collection could be observed in piglet 2, namely 7%, but no change in isotope dilution could be seen in piglet 1. These secondary isotope effects could only be observed in the 2 days cumulative urine, and not in the cumulative urines collected over shorter times. The non-cumulative urines collected at half-day periods showed a significant decrease in isotope dilution in THE and THF isolated from the urine collected after 1 day. No statistically significant isotope effects were observed with the metabolism of (3H)cortisol, except at 0.5 day when the specific activity in the cortolones was lower and that in THF was higher. However, at 0.5 day with THE and 1.0 day with THF and the cortolones the specific activities remained approximately 6% higher than that administered in the cortisol. Secondary isotope effects with tritiated cortisol may have occurred but because of the relatively large imprecision of the measurement (SD = 3-4% with THE and THF and the cortolones (SD approximately 8%) compared to the measurements of the 13C4 enrichment (SD approximately 2%) these effects could not statistically be proven.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenalectomy↗
PubMedDate not supplied

Pharmacokinetics of 14C-etretinate in healthy volunteers and two patients with biliary T-tube drainage.

The pharmacokinetic profile of 14C-etretinate, a retinoid that is effective in the treatment of psoriasis, was studied in six healthy male volunteers and two biliary T-tube patients. Following a 100 mg oral dose of 14C-etretinate (20 microcurie), etretinate and its major blood metabolites (etretin, isoetretin) were measured by HPLC and total carbon-14 was measured in blood, bile, urine, and feces by liquid scintillation counting. Etretinate was extensively metabolized in healthy volunteers and in T-tube patients. During the absorption phase, 75 per cent of the total radioactivity in the blood could be accounted for as etretinate, etretin, and isoetretin whereas these compounds accounted for only approximately 12 per cent of the blood radioactivity in T-tube patients over the same time period. The blood concentrations of etretinate, etretin, and isoetretin appeared to be substantially reduced in T-tube patients compared to those in healthy volunteers. A higher proportion of the total drug was excreted in the feces and bile of the T-tube patients (84 per cent) than in the feces of healthy volunteers (62 per cent). The major factor responsible for the observed decrease in etretinate blood concentrations following biliary cannulation appears to be the reduced absorption of etretinate due to the elimination of solubilizing bile salts in the duodenum. Carbon-14 related material was detected in urine and feces for as long as 3 weeks in healthy subjects supporting the previous observation that a long terminal elimination half-life exists for etretinate, even following a single dose of the compound.

Bile↗
PubMed1990

Distribution of mu, delta, and kappa opioid receptor binding sites in the brain of the one-day-old domestic chick (Gallus domesticus): an in vitro quantitative autoradiographic study.

Three highly specific opioid ligands--[D-Ala2,Gly-ol]-enkephalin (DAGO) for mu (mu) receptor sites, [D-Pen2,D-Pen5]-enkephalin (DPDPE) for delta (delta) sites, and U-69593 for kappa (kappa) sites--were used to determine the regional distribution of the three major subtypes of opioid receptor binding sites in the brains of 1-day-old domestic chicks by the technique of quantitative receptor autoradiography. Whilst there was a degree of heterogeneity in the binding levels of each of the ligands, some notable similarities existed in the binding of the mu and kappa ligands in several forebrain regions, and in the optic tectum of the midbrain where mu and delta binding was very high. In the forebrain there was a high level of binding of mu and kappa ligands in the hyperstriatum, and for the mu ligand there was a very distinct lamination of binding sites in hyperstriatum accessorium, intercalatum supremum, dorsale and ventrale. Levels of binding of the mu and kappa ligands were also high in nucleus basalis, and (for mu only) in the neostriatum. The distribution of binding of the delta specific ligand in the forebrain showed marked differences to that of mu and kappa, being particularly low in the hyperstriatum and neostriatum. Very high levels of labelling of delta binding sites were, however, found in the nucleus rotundus. Binding of the three ligands was generally low or absent in the cerebellum and medulla, apart from a distinct labelling of the granule cell layer by the mu-ligand. A kinetic analysis was made of the binding of the three ligands to whole forebrain sections using scintillation counting methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗
PubMed1991

Conditioning nerve crush accelerates cytoskeletal protein transport in sprouts that form after a subsequent crush.

To examine the relationship between axonal outgrowth and the delivery of cytoskeletal proteins to the growing axon tip, outgrowth was accelerated by using a conditioning nerve crush. Because slow component b (SCb) of axonal transport is the most rapid vehicle for carrying cytoskeletal proteins to the axon tip, the rate of SCb was measured in conditioned vs. sham-conditioned sprouts. In young Sprague-Dawley rats, the conditioning crush was made to sciatic nerve branches at the knee; 14 days later, the test crush was made where the L4 and L5 spinal nerves join to form the sciatic nerve in the flank. Newly synthesized proteins were labeled in motor neurons by injecting 35S-methionine into the lumbar spinal cord 7 days before the test crush. The wave of pulse-labeled SCb proteins reached the crush by the time it was made and subsequently entered sprouts. The nerve was removed and sectioned for SDS-PAGE and fluorography 4-12 days after the crush. Tubulins, neurofilament proteins, and representative "cytomatrix" proteins (actin, calmodulin, and putative microtubule-associated proteins) were removed from gels for liquid scintillation counting. Labeled SCb proteins entered sprouts without first accumulating in parent axon stumps, presumably because sprouts begin to grow within hours after axotomy. The peak of SCb moved 11% faster in conditioned than in sham-conditioned sprouts: 3.0 vs. 2.7 mm/d (p less than 0.05). To confirm that sprouts elongate more rapidly when a test crush is preceded by a conditioning crush, outgrowth distances were measured in a separate group of rats by labeling fast axonal transport with 3H-proline 24 hours before nerve retrieval.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Influence of methylxanthine-containing foods on theophylline metabolism and kinetics.

The metabolism and kinetics of 14C-labeled theophylline have been studied after intravenous doses of 100 mg to healthy subjects, keeping to their usual diets after 7 days of abstention from methylxanthine-containing foods and beverages and again after such abstention while taking caffeine and theophylline in tablet form. The metabolism of oral 14C-theophylline has also been investigated. Metabolites were separated and quantitated by ion-exchange column chromatography, ion-exchange paper chromatography, and liquid scintillation counting. Three major metabolites were found in urine in addition to theophylline, namely 3-methylxanthine, 1,3-dimethyluric acid, and 1-methyluric acid, and 2 minor metabolites were detected but not identified. The elimination kinetics were studied after intravenous administration; theophylline, 1,3-dimethyluric acid, and 1-methyluric acid were eliminated by first-order processes, while elimination of 3-methylxanthine was described by Michaelis-Menten kinetics. Abstention from methylxanthine-containing foods and beverages led to a significant decrease in the urinary elimination half-life of 14C from 9.8 to 7.0 hr (p less than 0.02) due to increases in the elimination constants for theophylline, 3-methylxanthine, and 1,3-dimethyluric acid. When the methylxanthine content of the methylxanthine-containing foods and beverages was replaced by caffeine and theophylline in table form, kinetics and metabolism of theophylline were the same as in subjects on usual diets.

Administration, Oral↗
PubMed1989

Detection of mRNA in flow-sorted cells.

Cells were sorted onto nitrocellulose filters which were saturated with a lysing cocktail designed to preferentially immobilize cellular mRNA. After washing, these filters were incubated with 32P-labeled specific DNA probes. We used the phorbol ester/lipopolysaccharide (PMA + LPS) co-induction of IL-1 mRNA and CD13 expression in U937 cells to demonstrate the specificity of the technique. In addition we used the abundant expression of c-fos in U937 to demonstrate linearity. IL-1 beta mRNA is readily discernable autoradiographically from as few as 5,000 PMA + LPS-induced cells sorted onto a filter. With liquid scintillation counting we demonstrate good linearity of the c-fos quantitation over the range of 1,000 cells to 60,000 cells per filter target. The technique is easily adapted to any sorting flow cytometer and should prove useful to help correlate any flow cytometric cell phenotype with specific mRNA abundance.

Flow Cytometry↗