Lipophilic Carrier Research Articles

Soluble filler as a dissolution profile modulator for slightly soluble drugs in matrix tablets

The purpose of this experimental work was the development of hydrophilic–lipophilic matrix tablets for controlled release of slightly soluble drug represented here by diclofenac sodium (DS). Drug dissolution profile optimization provided by soluble filler was studied. Matrix tablets were based on cetyl alcohol as the lipophilic carrier, povidone as the gel-forming agent, and common soluble filler, that is lactose or sucrose of different particle size. Physical properties of tablets prepared by melt granulation and drug release in a phosphate buffer of pH 6.8 were evaluated. In vitro studies showed that used filler type, filler to povidone ratio and sucrose particle size influenced the drug release rate. DS dissolution profile could be changed within a wide range from about 50% per 24 hours to almost 100% in 10 hours. The release constant values confirmed that DS was released from matrices by the diffusion and anomalous transport. The influence of sucrose particle size on the drug release rate was observed. As the particle size decreased, the drug release increased significantly and its dissolution profile became more uniform. Soluble fillers participated in the pore-forming process according to their solubility and particle size. Formulations containing 100 mg of the drug, 80 mg of cetyl alcohol, 40 mg of povidone, and 80 mg of either lactose or sucrose (particle size 250–125 μm) were considered optimal for 24-hour lasting dissolution of DS.

Effects of size and topology of DNA molecules on intracellular delivery with non-viral gene carriers

BackgroundEfforts to improve the efficiency of non-viral gene delivery require a better understanding of delivery kinetics of DNA molecules into clinically relevant cells. Towards this goal, three DNA molecules were employed to investigate the effects of DNA properties on cellular delivery: a circular plasmid DNA (c-DNA), a linearized plasmid DNA (l-DNA) formulated by single-site digestion of c-DNA, and smaller linear gene cassette generated by PCR (pcr-DNA). Four non-viral gene carriers were investigated for DNA delivery: polyethyleneimine (PEI), poly-L-Lysine (PLL), palmitic acid-grafted PLL (PLL-PA), and Lipofectamine-2000™. Particle formation, binding and dissociation characteristics, and DNA uptake by rat bone marrow stromal cells were investigated.ResultsFor individual carriers, there was no discernible difference in the morphology of particles formed as a result of carrier complexation with different DNA molecules. With PEI and PLL carriers, no difference was observed in the binding interaction, dissociation characteristics, and DNA uptake among the three DNA molecules. The presence of serum in cell culture media did not significantly affect the DNA delivery by the polymeric carriers, unlike other lipophilic carriers. Using PEI as the carrier, c-DNA was more effective for transgene expression as compared to its linear equivalent (l-DNA) by using the reporter gene for Enhanced Green Fluorescent Protein. pcr-DNA was the least effective despite being delivered into the cells to the same extent.ConclusionWe conclude that the nature of gene carriers was the primary determinant of cellular delivery of DNA molecules, and circular form of the DNA was more effectively processed for transgene expression.

Perireceptor events in taste.

The microenvironment at chemical receptor sites is important for ligand-receptor interaction as it can influence the entry, residence time or exit of odorant and sapid molecules. The perireceptor milieu at apical taste cell microvilli consists of taste pore mucus and secretions from salivary glands. The majority of taste buds are sheltered in epithelial folds of the foliate and circumvallate papillae where saliva is provided predominantly by the lingual von Ebner's glands (VEGs). To investigate possible saliva-tastant interactions, we have characterized a prominent 18 kDa secretory protein expressed in human, rat and pig VEGs. The human and rat VEG proteins share 60% sequence identity and, by virtue of their protein and gene structure, can be assigned to the lipocalin superfamily of lipophilic ligand carrier proteins. VEG proteins might function as transporters of hydrophobic molecules, for example bitter substances, like the nasal odorant-binding proteins that belong to the same protein family. Because binding experiments using various bitter substances have so far failed, and in light of the species-specific expression, other functions for VEG proteins must be considered. These include the protection of taste epithelia, pheromone transport and lipid binding.

Enfleurage, lipid recycling and the origin of perfume collection in orchid bees

Enfleurage, the extraction of elusive floral scents with the help of a lipophilic carrier (grease), is widely used in the perfume industry. Male neotropical orchid bees (Euglossini), which accumulate exogenous fragrances as pheromone analogues, use a similar technique. To collect fragrances, the bees apply large amounts of straight-chain lipids to odoriferous surfaces from their cephalic labial glands, which dissolve the volatiles, and the mixture is then transferred to voluminous hind-leg pockets. Here, we show that males do in fact operate a lipid conveyor belt to accumulate and concentrate their perfume. From the hind-leg pockets of caged male Euglossa viridissima, deuterated derivatives of carrier lipids were consecutively sequestered, shuttled back to the labial glands and reused on consecutive bouts of fragrance collection. Such lipid cycling is instrumental in creating complex perfume bouquets. Furthermore, we found that labial glands of male orchid bees are strikingly similar to those of scent-marking male bumblebees in terms of size, form and structure. This, and a prominent overlap in secretory products, led us to propose that perfume collection evolved from scent-marking in ancestral corbiculate bees.

Interphotoreceptor Retinoid-Binding Protein Is the Physiologically Relevant Carrier That Removes Retinol from Rod Photoreceptor Outer Segments

Light detection by vertebrate rod photoreceptor outer segments results in the destruction of the visual pigment, rhodopsin, as its retinyl moiety is photoisomerized from 11-cis to all-trans. The regeneration of rhodopsin is necessary for vision and begins with the release of the all-trans retinal and its reduction to all-trans retinol. Retinol is then transported out of the rod outer segment for further processing. We used fluorescence imaging to monitor retinol fluorescence and quantify the kinetics of its formation and clearance after rhodopsin bleaching in the outer segments of living isolated frog (Rana pipiens) rod photoreceptors. We independently measured the release of all-trans retinal from bleached rhodopsin in frog rod outer segment membranes and the rate of all-trans retinol removal by the lipophilic carriers interphotoreceptor retinoid binding protein (IRBP) and serum albumin. We find that the kinetics of all-trans retinol formation in frog rod outer segments after rhodopsin bleaching are to a good first approximation determined by the kinetics of all-trans retinal release from the bleached pigment. For the physiological concentrations of carriers, the rate of retinol removal from the outer segment is determined by IRBP concentration, whereas the effect of serum albumin is negligible. The results indicate the presence of a specific interaction between IRBP and the rod outer segment, probably mediated by a receptor. The effect of different concentrations of IRBP on the rate of retinol removal shows no cooperativity and has an EC50 of 40 micromol/L.

Antiseptic Efficacy of a Low-Dosed Topical Triclosan/Chlorhexidine Combination Therapy in Atopic Dermatitis

The topical application of triclosan as an antistaphylogenic antiseptic has proven beneficial in atopic dermatitis. Especially in lipophilic carriers, triclosan is applied in a concentration range between 1 and 5%, usually 2%. However, as a phenol, triclosan is not undisputed and may result in local exacerbation of the disease by eliciting irritative secondary reactions, especially in high concentrations. Chlorhexidine is also an antiseptic which is very effective against Staphylococciand nearly equivalent to triclosan with respect to its antistaphylogenic efficacy. In light of this, the combination of the two active substances in very low concentrations offers a possible option of using the additive effects of the two substances to minimize the risk of side effects. In a uniform W/O emulsion carrier alternatively containing 0.3% triclosan combined with 0.34% chlorhexidine dihydrochloride or 2.0% triclosan, the antibacterial efficacy against Gram-positive skin bacteria could be proven in a preclinical comparison with a reference preparation containing fusidic acid. Subsequently, the pathogen-reducing effect was examined in a clinical study of the influence on clinical severity in patients with atopic dermatitis. Both investigation methods showed that the two test preparations were slightly inferior to the reference preparation, but result in the same degree of pathogen reduction and improvement in the severity of existing atopic dermatitis in direct comparison. The overall results support the conclusion that a combination of triclosan and chlorhexidine in low concentrations as well as the existing antiseptic standard of a 2% triclosan preparation are suitable for pathogen reduction and thus for improving atopic dermatitis.

Characterization of Lipophilic Gemcitabine Prodrug−Liposomal Membrane Interaction by Differential Scanning Calorimetry

Gemcitabine is an anticancer agent rapidly deaminated to the inactive metabolite 2',2'-difluorodeoxyuridine. Its stability as well as bioavailability can be increased by making prodrugs. A series of lipophilic prodrugs of gemcitabine were synthesized by linking the 4-amino group with valeroyl, lauroyl, and stearoyl linear acyl derivatives. We studied, by the differential scanning calorimetry technique, and compared the interaction of pure gemcitabine and its prodrugs with dimyristoylphosphatidylcholine and distearoylphosphatidylcholine vesicles with the aim of demonstrating if the gemcitabine prodrug is more able than the pure gemcitabine to interact with lipid vesicles employed both as model biomembranes and as carriers in the transport of antitumor drugs. These studies, carried out by static and kinetic calorimetric measurements, give evidence that the increase of the prodrug's lipophilic character improves the interaction with lipid bilayers, favoring the absorption through the lipid barriers and allowing the liposomes to work (when the prodrug is inserted inside the vesicles) as a lipophilic carrier which is able to deliver the drug near the cell surface. The use of different prodrugs modified in their lipophilic character, of different kinds of vesicles (multilamellar and unilamellar), and of different kinds of vesicles forming phospholipids permitted us to determine the better equilibrium between in-vesicle solubility and through-vesicle diffusion of the drug, important in the preformulative studies of antitumor carriers based on phospholipid formulations. Such studies suggest that the prodrug lipophilic tail should modulate the transport and the release of gemcitabine inside the cellular compartments, and the efficiency of the liposomal system is related to the length of the prodrug's acyl chain which has to match the phospholipid acyl chain allowing or retarding the migration through the lipid release device.

Affinity membranes for the extraction of Cd 2+ metal ions by facilitated transport ensured by a new thiacalix[4]arene complexing agent incorporated in supported liquid membranes (SLM)

A thiacalix[4]arene dissolved in NPOE for incorporation in a supported liquid membrane, is shown to ensure a transmembrane transport flux of Cd 2+ ions with an order of magnitude higher than that obtained with a very lipophilic carrier such as Lasalocide A, according to a mechanism of active facilitated transport (coupled to a pH gradient). Liquid–liquid (water-NPOE) extraction experiments confirmed the good affinity of the thiacalix[4]arene for the Cd 2+ ions at the interface between an aqueous medium of pH = 8 and NPOE organic phase, as well as its almost complete release in water when the pH of the aqueous phase is changed to acid.

Synthesis and Evaluation of Novel Prodrugs of Foscarnet and Dideoxycytidine with a Universal Carrier Compound Comprising a Chemiluminescent and a Photochromic Conjugate

To facilitate intracellular delivery of hydrophilic drugs, a general lipophilic carrier molecule was designed and synthesized. The carrier comprised a chemiluminescent-photochromic conjugate that potentiates diffusion across cell membranes to enhance intracellular uptake of the drug. The designed mechanism involves activation of the chemiluminescent moiety by intracellular oxygen free radicals and intermolecular energy transfer of the excited state energy to the photochromic moiety to result in release of the drug to allow the desired pharmacological effect to occur. Prodrugs of foscarnet and dideoxycytidine with several carriers caused suppression of a human immunodeficiency virus infection in human cultured macrophages that was up to five times more effective than the drug alone. Successful in vivo efficacy testing of prodrug has been accomplished by demonstrating the suppression of a retroviral infection of Friend leukemia virus in mice. Acute toxicity studies of the carrier indicated that it was nontoxic. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1320–1336, 2004

Facilitated transport of saccharides through a supported liquid membrane containing a neutral lipophilic resorcinarene carrier

The facilitated transport of several types of saccharidess has been studied across a supported liquid membrane containing a resorcinarene carrier. The rate-determining step is believed to be the migration of a carrier-saccharide-water ternary complex in the organic solvent. The transport kinetics obey a saturation law, that allows the calculation of the stability constants of the various complexes. The stability constants are related to the saccharide structures: important factors are chain length, configuration and substitution of key hydroxyl groups.

Kit Formulation for the Preparation of Radioactive Blue Liposomes for Sentinel Node Lymphoscintigraphy

A radioactively labeled blue liposome formulation was developed for use in presurgical lymphoscintigraphy and intraoperative sentinel node localization to avoid the differing injection site clearance kinetics of the conjunctive use of separate formulations of low molecular weight blue dye and radioactively labeled macromolecular sulfur colloid. Blue liposomes containing glutathione in the internal aqueous phase were prepared from blue dyed lipids obtained by covalently binding Reactive Blue II to phosphatidylethanolamine (PE) fractions of phospholipid extracts. Four phospholipid extracts with differing PE fractions and a centrifugation technique were evaluated with the goal of maximizing the blue color intensity of the formulation. Stability of the formulations was evaluated by studying radiolabeling efficiency (using a membrane permeable lipophilic carrier of the commonly used diagnostic radionuclide, technetium-99m) and particle-size distribution over 30-60-day periods. Blue color was not altered by varying the PE content, while centrifugation was an effective and convenient method to maximize the blue color intensity of the final preparation. The particle size distribution of the prepared liposomes ranged from 200-300 nm (considered ideal for lymphoscintigraphy studies) and did not change significantly, while radiolabeling efficiency exceeded 80% for up to 1 month. The described kit formulation for the preparation of radiolabeled blue liposomes is suitable for commercial production allowing widespread clinical use. The combination of a means of visual identification and tracking of the liposomes through the lymphatic channels along with the ability to trace the preparation using standard radiation detection instrumentation provides the surgeon with an improved radiolabeled compound for lymphoscintigraphy and intraoperative sentinel lymph node identification.

Mammalian lipocalin-type prostaglandin D2 synthase in the fluids of the male genital tract: putative biochemical and physiological functions.

Prostaglandin D2 synthase (PGDS) is a major epididymal secretory protein in several species. We quantified PGDS in ram and bull semen using a specific antiserum. Strong variations in PGDS concentration existed between animals. In the bull, the highest concentrations were found preferentially in animals with normal or high fertility, as was previously suggested. However, low concentrations were found in males with all ranges of fertility, suggesting that the function of PGDS either is not necessary for male fertility or can be assumed by other proteins when its concentration is low. In the ram and stallion, cDNA and deduced protein sequences of PGDS were obtained by reverse transcription-polymerase chain reaction and showed that PGDS possessed the sequences involved in the three-dimensional folding characteristic of the lipocalin family and a cysteine at position 65 that is involved in the enzymatic activity. The enzymatic activity of PGDS was estimated in the ram by in vitro incubation of epididymal-isolated tubules with radioactive arachidonic acid. Prostaglandin (PG) D2 represented approximately 10% of the PGs produced in the lumen, irrespective of the presence or absence of luminal PGDS, suggesting that this protein is not involved in PGD2 biosynthesis. These results were corroborated by the absence of conversion of PGH2 to PGD2 when epididymal fluids were incubated with PGH2. In the rat, inhibition of PG biosynthesis in vivo by nonsteroidal anti-inflammatory drugs for 60 days did not change spermatozoa mobility or male fertility. It is likely that PGDS, which has a structure similar to that of lipocalin, functions as a lipophilic carrier protein, because we have shown that epididymal PGDS binds retinoic acid and testosterone in vitro.

Disubstituted tetrahydro-2H-1,3,5-thiadiazine-2-thiones as lipophilic carriers for glutamine and glutamic acid

L-​Glutamine and glutamic acid were incorporated in a tetrahydro-​2H-​1,​3,​5-​thiadiazine-​2-​thione (THTT) skeleton contg. different alkyl, cycloalkyl and aralkyl groups at N3 of the ring system. These THTT derivs. revealed high lipophilicity compared with L-​glutamine and glutamic acid. The degrdn. kinetics were studied -​in vitro- using aq. buffer solns. of pH values: 1.2, 6.0, 7.4, 7.8 and 9.0 at 37°. From the pH profile, the degrdn. was accounted for, in terms of specific base-​catalyzed reactions. All of the compds. however, showed higher acid-​stability.

Inhibition of DNA methyltransferase inhibits DNA replication.

Ectopic expression of DNA methyltransferase transforms vertebrate cells, and inhibition of DNA methyltransferase reverses the transformed phenotype by an unknown mechanism. We tested the hypothesis that the presence of an active DNA methyltransferase is required for DNA replication in human non-small cell lung carcinoma A549 cells. We show that the inhibition of DNA methyltransferase by two novel mechanisms negatively affects DNA synthesis and progression through the cell cycle. Competitive polymerase chain reaction of newly synthesized DNA shows decreased origin activity at three previously characterized origins of replication following DNA methyltransferase inhibition. We suggest that the requirement of an active DNA methyltransferase for the functioning of the replication machinery has evolved to coordinate DNA replication and inheritance of the DNA methylation pattern.

Transdermal delivery of antiparkinsonian agent, benztropine. I. Effect of vehicles on skin permeation

The influence of pH and various lipophilic and hydrophilic vehicles on the epidermal permeation of benztropine (BZ) free base and its mesylate salt were studied in vitro using the hairless mouse (HLM) and human cadaver (HC) skin membranes. The pH-partition behavior of BZ base (p K a=10) was examined using n-octanol and Britton–Robinson buffers over the pH range of 5–12. Unexpectedly, the ionized species of BZ yielded a high partition coefficient (log K octanol/water=2.14), which was reflected by its relatively high skin permeability ( P=1.6×10 −2cm h −1). BZ base delivered from a lipophilic vehicle with a solubility parameter range of 7.1–10.3 (cal cm 3) 1/2 exhibited a significantly enhanced rate of permeation as compared to that attained from a hydrophilic vehicle of solubility parameter range between 12.5–23.4 (cal cm 3) 1/2. Among the neat solvents examined, a lipophilic carrier, isopropyl myristate (IPM) provided the most enhancing effect on the permeation of BZ base. In addition, the neat IPM carrier offered the maximum BZ base flux of 150 μg per cm 2 h −1 across HC skin, which was approximately 16 times greater than the target delivery rate of BZ from a 10-cm 2 device. In comparison, BZ base exhibited a 2–60 times greater flux than BZ mesylate when delivered from the neat solvents. However, interestingly enough, the binary cosolvents consisting of IPM and short-chain alkanols such as ethanol (EtOH), isopropanol (iPrOH), and tertiary butanol (tBtOH), in particular a 2:8 combination, produced a marked synergistic enhancement of BZ flux from the mesylate salt, whereas a retarding effect was noticed for the permeation of BZ base. The enhancement potency for the BZ mesylate permeation increased linearly with the carbon number of the branched alcohols present in the binary mixtures. A tBtOH-IPM (2:8) combination produced the highest BZ flux from the mesylate salt, i.e., 2016 mg per cm 2 h −1, which was 100-fold greater than from water and 44–540-fold greater than the individual neat solvents, respectively. The observed permeation enhancement of BZ mesylate by the alkanol-IPM mixtures was probably as a result of a combination of decreasing barrier ability of the stratum corneum by the binary vehicles and moderately partitioning BZ mesylate through the viable epidermis/dermis.

Topical use of local anesthetics in neonates.

Various local anesthetics as in lidocaine ointment, amethocaine cream and EMLA cream are used topically for minor invasive interventions, such as venipuncture, both in children and adults. Since neonates have a nervous system that, albeit immature, enables them to feel pain, analgesia for these procedures is also indicated. Several studies in neonates have been carried out to establish effectiveness and safety of topically applied local anesthetics. These studies are reviewed in order to assess effectiveness and safety. A Medline search was made in order to review all studies on effectiveness and safety of topical use of local anesthetics in neonates. Effectivity or safety studies using local anesthetics for circumcision were rejected. Seven studies on effectiveness were found: Three studies examined lidocaine ointment and four examined EMLA cream. Effectiveness of lidocaine ointment was questionable in two studies and negative in one. Effectiveness of EMLA cream was positive in two studies and negative in the other two. Four studies were found on safety of EMLA cream. All studies indicated that use of EMLA cream was safe. The poor effectiveness found in the reviewed studies is possibly due to too long an application time, a lipophilic carrier used and difficulties in assessing pain. The time of application is often based upon studies in children. Since the skin of neonates acts more as a mucosa than as mature skin the local anesthetics are able to cross this barrier more rapidly. Also a high bloodflow in the heel enhances the uptake of the drug. The application time in neonates should therefore be reduced compared to children. The use of a lipophilic carrier should be avoided since a lipophilic carrier impedes the local anesthetic to be absorbed, leading to reduced effect. Various methods of pain assessment were being used. Since not all methods used are validated it is difficult to obtain an objective end point. The articles reviewed are non conclusive in their results of effective analgesia. Due to a lipophilic base form and a hydrophilic matrix EMLA cream is most effective. An application time of 30 minutes is recommended. In spite of the present precautions due to fear of methemoglobinemia, use of EMLA cream proved to be safe when used once a day. Since the clinical situation often requires more than one application a day, more research is needed to establish a safe and effective local anesthetic which can be applied topically several times a day in the neonate.

Iron-salicylate complex induces peroxidation, alters hepatic lipid profile and affects plasma lipoprotein composition

Iron overload, with its associated toxic effects, has serious health consequences and results in damage to the liver, heart and other organs. Salicylate may be used as the lipophilic carrier, transporting more iron into hepatocytes. In this study, we examined the effect of the combined administration of these compounds on plasma lipid profile and lipoprotein composition, as well as on hepatic lipid concentration. Male Spraque-Dawley rats were injected i.p. with Fe (15 mg/kg weight). This injection was repeated 24 h later with a gavage of sodium salicylate (700 mg/kg). Control rats received 0.9% NaCl only. The peroxidation indices TBARS ( P<0.001) and conjugated dienes ( P<0.05) significantly increased in the blood (50 and 122%, respectively) and liver (333 and 101%, respectively) of Fe–salicylate-treated rats. Concomitantly, blood and liver arachidonic acid content was diminished by iron treatment. In parallel, the plasma lipid profile was markedly affected in Fe–salicylate treated-rats. Lower plasma concentrations of total cholesterol (25%, P<0.0001) cholesteryl ester, (34%, P<0.001) and high-density lipoprotein-cholesterol (50%, P<0.001) were observed. Lipoprotein composition analysis revealed enrichment of free cholesterol and depletion of cholesterol ester in very low-density, intermediate-density, low-density and high-density (HDL 2, HDL 3) lipoproteins. Furthermore, SDS-polyacrylamide gel electrophoresis revealed several alterations in the apolipoprotein distribution of these lipoproteins. The activity of lecithin:cholesterol acyltransferase was unchanged and could not account for the reduction of cholesterol esterification. As for the plasma, the liver exhibited a significant ( P<0.001) decrease in total cholesterol (2.42±0.07 versus 1.89±0.06 mg/g liver), essentially due to a reduction in cholesteryl ester (0.93±0.07 versus 0.51±0.03 mg/g liver, P<0.001). Again, the activity of ACAT (dpm/mg microsomal protein) was not lower (12 700±1250) than that of controls (9650±1080). Thus, the iron–salicylate was able to induce peroxidation and to profoundly affect the intravascular and intrahepatic lipid, and plasma lipoprotein metabolism. Additional work is needed to elucidate the mechanisms involved in the underlying lipid and lipoprotein abnormalities.

Determinants of Membrane Association for Poliovirus Protein 3AB

Poliovirus protein 3AB may serve as the lipophilic carrier of a protein primer (VPg or 3B) used for the initiation of genomic viral RNA synthesis. In order to study the membrane-protein interactions of 3AB required for its role in poliovirus RNA replication, we have developed an in vitro membrane association assay capable of distinguishing membrane-bound from non-membrane-bound proteins that are cotranslated together in the presence of canine microsomal membranes. This assay utilizes equilibrium sedimentation analysis in high density sucrose gradients to measure membrane association of both wild type and mutated forms of 3AB. Using this assay and other biochemical assays, we have identified the following properties of the 3AB-membrane interaction: (a) 3AB is able to post-translationally associate with microsomal membranes, (b) 3AB is able to associate with membranes in a manner consistent with that of an integral membrane protein, (c) 3AB contains a critical hydrophobic sequence within the carboxyl-terminal half of the protein that is required for membrane association, and (d) the introduction of charged residues into this hydrophobic sequence disrupts the 3AB membrane-protein interaction. Taken together, these studies indicate that poliovirus protein 3AB associates tightly with biological membranes de novo in a manner that would allow it to serve as a lipophilic anchor for the assembly of the poliovirus RNA replication complex.

Semivolatile long chain C6–C17 alkyl nitrates as trace compounds in air

The analytical chemistry of long chain alkyl nitrates with carbon numbers up to 26 is reported for the first time. The thermolabile long chain alkyl nitrates can be analysed by capillary gas chromatography on short columns (5–10 m) with thin films (0,1–0,25pm). The short column technique combined with on-column injection and the use of hydrogen at high flow rates prevents the thermal degradation of the thermolabile semivolatile organonitrates during the GC separation. HRGC/ECD, and HRGC/MSD using 46 amu as the signal reveal a standard pattern of isomeric organonitrates surprizingly up to only C17 in semirural air. The concentrations decrease continously from 7,3 ng Nm −3 corresponding to 1,11 pptv for the hexyl nitrates to 1,7 ng NM −3 corresponding to 0,15 pptv for the tetradecyl nitrates. No semivolatile alkyl nitrates could be detected in particulates (≥2 micron) collected by a glass fibre filter. Alkyl nitrates are known as reservoir species of NO/NO 2 in air. Their biological potential is also well established. Long chain alkyl nitrates form lipophilic carriers for NO x and therefore nitric acid and nitrate ions.

Metalloporphyrin chloride ionophores: induction of increased anion permeability in lung epithelial cells

5,10,15,20-Tetraphenyl-21H,23H-porphine manganese (III) chloride [TPPMn(III)] is a positively charged lipophilic anion carrier that is widely used as a Cl- sensor. TPPMn(III) increased anion permeability of cultured mouse lung epithelial (MLE) cells as measured by short-circuit current (ISC) to a level similar to that induced by forskolin analogues. Anion permeability was also studied in cultured human lung epithelial (A549) cells by measurement of the rates of change of fluorescence of the anion sensitive fluorescent dye, 6-methoxy-N-(3-sulfopropyl)quinolinium (SPQ). In these studies, cells were incubated with SPQ in SO2-4- medium, washed free of extracellular SPQ, and then perfused with medium containing anions that are known to quench SPQ fluorescence. The effect of TPPMn(III) on anion transport was then determined either microscopically in single cell studies or using cell monolayers mounted in a front face fluorimeter. TPPMn(III) in the range from 1 to 100 micrograms/ml induced a dose-dependent increase in Br- transport. The half-maximal quenching effect was estimated to be approximate 5 micrograms/ml. TPPMn(III) increased the rates of fluorescence quench of anions by up to fourfold. TPPMn(III) was without effect on -Ca2+-i level in A549 cells as measured with fura 2-AM. This indicates that TPPMn(III) effects were not mediated through effects on Ca+2 -activated Cl- channels, or by compromise of energy metabolism or membrane integrity of the cells. This study suggests that TPPMn(III) and, by extension, other lipophilic Mn(III) or Co(III) derivatives wherein the selectivity of lipophilicity is altered, could increase the anion permeability of biological membranes, and suggests a new approach for treatment of diseases such as cystic fibrosis, where transport of Cl- is defective.