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PubMed1999

Simultaneous use of sodium deoxycholate and dipotassium glycyrrhizinate enhances the cellular transport of poorly absorbed compounds across Caco-2 cell monolayers.

The absorption-enhancing effect of a combination of sodium deoxycholate and dipotassium glycyrrhizinate in Caco-2 cell monolayers has been compared with that of the enhancers when used alone, and the mechanism of the enhancement was partially elucidated. The effect of the combined compounds was evaluated by measurement of transepithelial electrical resistance (TEER) and the cellular permeability of the water-soluble model compounds sodium fluorescein (MW 376.3) and fluorescein isothiocyanate dextran (MW 4400). The TEER of the monolayers decreased with increasing concentrations of dipotassium glycyrrhizinate in combination with 0.02% (w/v) sodium deoxycholate for 20 min, and reached a minimum at 1% (w/v) dipotassium glycyrrhizinate. Although a combination of 0.02% (w/v) sodium deoxycholate and 1% (w/v) dipotassium glycyrrhizinate enhanced the cellular permeability of sodium fluorescein and fluorescein isothiocyanate dextran, 0.02% (w/v) sodium deoxycholate and 1% (w/v) dipotassium glycyrrhizinate alone had no effect on either the TEER of the monolayers or the cellular transport of the water-soluble compounds. Sequential and separate exposure of the monolayers to each enhancer for 10 min had no effect on the TEER, but a marked decrease in TEER was observed when both compounds were used in combination. The enhancing effect of the combination of sodium deoxycholate and dipotassium glycyrrhizinate was inhibited by H7, a protein kinase C (PKC) inhibitor, suggesting that dipotassium glycyrrhizinate might enhance the activation of PKC via sodium deoxycholate. The combined use of these two enhancers had no toxic effects. These results provide useful, basic information on the action of these absorption enhancers on drugs for which absorption is limited owing to polarity or molecular size, or both.

Absorption↗
PubMed1998

Actions of the pyrethroid insecticides cismethrin and cypermethrin on house fly Vssc1 sodium channels expressed in Xenopus oocytes.

Voltage-sensitive sodium channels encoded by the Vssc1 gene of the house fly (Musca domestica) were expressed in Xenopus laevis oocytes in combination with the tipE gene product of Drosophila melanogaster and were characterized by two-electrode voltage clamp. Vssc1/tipE sodium channels expressed in oocytes were highly sensitive to tetrodotoxin; half-maximal inhibition of sodium currents by tetrodotoxin was obtained at a concentration of 2.4 nM. Cismethrin, a pyrethroid that produces Type I effects on intact nerve, slowed the inactivation of sodium currents carried by Vssc1/tipE channels during a depolarizing pulse and induced a tail current after repolarization that decayed with a first-order time constant of approximately 650 ms. The voltage dependence of activation and steady-state inactivation of cismethrin-modified channels were shifted to more negative potentials. Cypermethrin, a pyrethroid with Type II effects on intact nerve, also prolonged the inactivation of Vssc1/tipE sodium channels and induced a tail current. However, the cypermethrin-induced tail current was extremely persistent, decaying with a first-order time constant of approximately 42 s. Unlike cismethrin, the effect of cypermethrin was use dependent, requiring repeated depolarizing pulses for the full development of modified sodium currents. The divergent effects of cismethrin and cypermethrin on Vssc1/tipE sodium channels expressed in oocytes are consistent with the actions of these and related compounds on sodium channels in invertebrate and vertebrate nerve preparations and provide insight into the mechanisms underlying the production of Type I and II effects on neuronal excitability.

Animals↗
PubMed2005

Cardiac reporter gene imaging using the human sodium/iodide symporter gene.

OBJECTIVE: Imaging of reporter gene expression holds promise for noninvasive monitoring of cardiovascular molecular therapy. We investigated the feasibility of myocardial gene expression imaging in living rats using the human sodium/iodide symporter gene (hNIS) and widely available scintigraphic techniques. METHODS: We injected adenovirus expressing hNIS under control of cytomegalovirus promoter (Ad(hNIS)) directly into left ventricular myocardium of Wistar rats. For detection of reporter gene expression, dynamic gamma-camera imaging was performed following intravenous injection of (123)Iodide or (99m)Technetium. RESULTS: For both radiotracers, focal cardiac accumulation was identified as early as 10 min, and remained detectable until 2 hrs after injection, while it was not present in animals injected with LacZ control virus. Intensity of tracer accumulation gradually decreased when decreasing titers of Ad(hNIS) were applied. Treatment with sodium perchlorate (a blocker of hNIS) abolished cardiac tracer uptake after Ad(hNIS)-infection. Serial imaging after cardiac gene transfer demonstrated a peak of tracer signal between days 1 and 3, and a subsequent decrease until day 12. Postmortem analysis of hearts yielded significant correlation between in vivo radiotracer accumulation and ex vivo gamma-counting. Autoradiography demonstrated specific regional radioactivity in Ad(hNIS)-infected myocardial areas. CONCLUSIONS: hNIS offers a practical and reliable approach for myocardial gene expression imaging. Using suitable vectors, hNIS may be coexpressed with therapeutic genes or stably expressed in stem cells for future monitoring of cardiovascular molecular therapy.

Animals↗
PubMed2002

Sodium-iodide symporter (NIS)-mediated accumulation of [(211)At]astatide in NIS-transfected human cancer cells.

The cellular expression of the sodium iodide symporter (NIS) has been shown to confer iodide-concentrating capacity in non-thyroid cell types. We examined the role of NIS in the uptake of the alpha-particle emitting radiohalide [(211)At]astatide in the UVW human glioma cell line transfected to express NIS. [(211)At]Astatide uptake is shown to be NIS-dependent, with characteristics similar to [(131)I]iodide uptake. These studies suggest [(211)At]astatide as a possible alternative radionuclide to [(131)I]iodide for NIS-based endoradiotherapy, and provide a model for the study of [(211)At]astatide behavior at a cellular level.

Astatine↗
PubMed2002

Mast cell dynamics and involvement in the development of peritoneal adhesions in the rat.

Mast cells have been implicated in the ethiopathology of post-operative peritoneal adhesions. However an evaluation of their role in this condition is missing. Adhesions were induced in rats using small intestinal scraping. These rats or rats injected ip with either Stem Cell Factor (SCF) or nedocromil sodium or compound 48/80 (day 0-20) were sacrificed for grading of peritoneal adhesions, for evaluating mast cells and inflammatory cells in adhesions and peritoneal lavage (histochemical staining) and for histamine content (peritoneal lavage, radioenzymatic assay) on days 1-21. Mast cell sonicate was added to intestinal fibroblast and their proliferation was assessed (cell counting). All the rats developed adhesions (day 1) and after 3 days the adhesion score remained constant. Early adhesions were avascular and made of fibrinous exudate containing many mast cells. Thereafter adhesions became denser, and the number of stainable mast cells decreased and then stabilized. On the first few days, inflammatory cells in the peritoneal lavage increased while mast cells and histamine content were significantly reduced indicating their activation. Injection of SCF for 1 week slightly increased peritoneal adhesion formation while nedocromil sodium reduced their development. Compound 48/80 had no significant influence. Addition of mast cell sonicate to normal intestine or to peritoneal adhesion fibroblasts resulted in a significant increase of fibroblast proliferation. In conclusion, mast cell presence correlated with the establishment of peritoneal adhesions, and their pharmacological modulation influenced adhesion formation. In vitro mast cell induced fibroplasia. Therefore, mast cells have a profibrogenic role in this model of peritoneal adhesions.

Animals↗
PubMed1997

Comparative cytotoxicity of cisplatin, sodium selenite and selenium-cisplatin conjugate [(NH3)2Pt(SeO3)]; changes of blood platelet activation.

The cytotoxic effects of a novel compound, conjugate Se-Pt [(NH3)2Pt (SeO3)] on blood platelet function (aggregation, release of adenine nucleotides) were studied. Contrary to the action of cisplatin or selenite alone, [(NH3)2Pt(SeO3)] did not inhibit ADP-induced platelet aggregation, thrombin-induced release of adenine nucleotides from platelets, and had no effect on the metabolism of platelet arachidonate. The tested compound seems to be less toxic than cisplatin alone, and has no effect on blood platelet activation.

Adenine Nucleotides↗
PubMed1975

Kinetic and equilibrium studies on the activation of Escherichia coli K12 tryptophanase by pyridoxal 5'-phosphate and monovalent cations.

An improved purification of Escherichia coli K12 tryptophanase is presented. It is shown that the apoenzyme crystals, oxidized by exposure to air, can be reactivated by treatment with a reducing agent. The titration of sulfhydryl groups shows that four --SH groups are exposed and two are masked per protomer. The influence of two effectors, monovalent cations and the coenzyme pyridoxal 5'-phosphate, on the reactivity of --SH groups and the enzymatic activity was investigated. The --SH groups react more slowly in holo- than in apoenzyme in the presence of potassium ions. If these ions are replaced by sodium ions, the reactivity becomes the same. Potassium and ammonium ions, both activators, give sigmoidal activation curves. The sodium ion is a Michaelian inhibitor of potassium activation. The binding of pyridoxal 5'-phosphate was examined by kinetics and at equilibrium. The kinetics are shown to be very slow; the rate constants of the forward and reverse reactions have been measured. The binding equilibrium, examined with 3H-labeled pyridoxal 5'-phosphate, gives one site per protomer with a K-D value of (3.2 plus or minus 0.8) times 10-7 M. The K-m for pyridoxal-P was determined by activity measurements. The binding equilibrium is attained after several hours, giving a value of 4.2 times 10-7 M, being nearly identical with the dissociation constant and 5 times smaller than previously reported.

Apoenzymes↗
PubMed1973

The electrical activity of canine cardiac Purkinje fibers in sodium-free, calcium-rich solutions.

Propagated action potentials can be obtained in canine cardiac Purkinje fibers exposed to Na-free solutions containing no inorganic cation other than Ca and K. Essentially similar action potentials are obtained if Na is replaced by tetraethylammonium (TEA), tetramethylammonium (TMA), or choline. In a solution containing 128 mM TEA and 16.2 mM Ca the characteristics of these electrical responses were: maximum diastolic potential, -59 +/- 3.3 mV; overshoot, 20 +/- 6.8 mV; maximum upstroke velocity, 3.7 +/- 2.3 V/s; conduction velocity, 0.1 m/s; and action potential duration, 360 +/- 45 ms. The magnitude of the overshoot varied with log Ca(o) with a slope of about 30 mV/10-fold concentration change. The upstroke velocity was an approximately linear function of Ca(o). The active response was greatly diminished or abolished by Mn and D-600 but was unaffected by tetrodotoxin. These Ca-dependent responses appeared in a region of transmembrane potential (about -50 mV) at which the rapid Na-dependent upstroke is abolished even when Na is present.

Action Potentials↗
PubMed2000

Mechanism of action of the potent sodium-retaining steroid 11, 19-oxidoprogesterone.

We have demonstrated previously that a planar conformation of the molecular frame is required for steroids to acquire optimal sodium-retaining activity and binding properties to the mineralocorticoid receptor (MR). One of the most active sodium-retaining compounds tested in those studies was 11, 19-oxidoprogesterone. Despite its biological potency, the relative affinity of 11,19-oxidoprogesterone for the MR is 5-fold lower than that of 21-deoxycorticosterone and 10-fold lower than aldosterone. Such a discrepancy may be assigned to uncommon biopharmacological properties of this synthetic steroid or an unusual molecular mechanism of action. In this work, we studied the biopharmacological and mechanistic features of 11,19-oxidoprogesterone. We show that both the pharmacokinetic properties of 11,19-oxidoprogesterone and its ability to transform and translocate the MR into the nucleus are undistinguishable from aldosterone. However, the capability of the serine/threonine phosphatase inhibitor tautomycin to impair nuclear translocation of the aldosterone-MR complex is not observed for the 11,19-oxidoprogesterone-MR complex. In addition, the binding properties of both steroids are differentially affected by modification of crucial lysyl residues of the MR. Kinetic studies performed on the aldosterone-MR complex in the presence of low concentrations of oxidopregnane suggest that 11,19-oxidoprogesterone may bind to the MR in a different binding site from the aldosterone binding pocket. Consistent with this postulate, a biologically inactive dose of 0.6 ng of oxidopregnane is able to potentiate the mineralocorticoid effect of a suboptimal dose of aldosterone.

Aldosterone↗
PubMed2000

Gel-derived materials of a CaO-P(2)O(5)-SiO(2) system modified by boron, sodium, magnesium, aluminum, and fluorine compounds.

Bioactive glass-ceramic materials of the CaO-P(2)O(5)-SiO(2) system modified by adding boron, magnesium, sodium, fluorine, and aluminum were obtained using the sol-gel method. Gel-derived materials were produced in the pellet form obtained by compression of powders as well as in coatings on glass slides. The materials obtained were examined in vitro with regard to the ability of calcium phosphate layer to form on the material surface as the result of contact with simulated body fluid (SBF). SBF pH changes and calcium solubility in this solution were determined and scanning electron microscopy, energy-dispersive X-ray analysis, and infrared spectroscopy studies were conducted before and after contact of the materials with SBF. The gels modified by aluminum were amorphous, whereas the sodium and fluorine additives promoted the bulk crystallization of gel-derived materials. The ability of calcium phosphates to crystallize on the surface of gel-derived materials depended only slightly on the types of additives applied, and the character of this dependence was different from that observed in melted glasses. Moreover, to estimate the biocompatibility of gel-derived coatings, we examined the proliferation, collagen synthesis, adhesion, and morphology of fibroblasts (NRK cells) cultured in the presence of gel-derived materials. The results of these experiments showed that none of the tested materials significantly reduced any cell function.

Animals↗
PubMed1988

Cell growth dynamics in long-term bladder carcinogenesis.

A biologically based probabilistic model of the carcinogenic process has been developed based on a two-stage theory of carcinogenesis. The model has been validated utilizing experimental urinary bladder carcinogenesis studies in the rat, with an emphasis on quantification of cell dynamics. Critical parameters tracked through this process include mitotic rates, cell loss and birth rates, and irreversible cellular transitions from normal to initiated to transformed states. Analyses demonstrate the sensitivity of tumor incidence to the timing and magnitude of changes to these cellular variables. Modeling has been applied to genotoxic compounds, such as N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide, and non-genotoxic compounds, such as sodium saccharin. For the latter compounds, complex administration regimens have been studied, including two-generation experiments, initiation-promotion experiments, and sodium saccharin administration following ulceration and regenerative hyperplasia. Modeling indicates that the effects of such compounds can be explained entirely on the basis of cytotoxicity and consequent hyperplasia. Quantitative modeling based on biological processes has the potential for direct application to carcinogenic risk assessment.

Cell Division↗
PubMed1983

Batrachotoxin-induced depolarization and [3H]batrachotoxinin-a 20 alpha-benzoate binding in a vesicular preparation from guinea pig cerebral cortex.

The sodium channel-specific agent batrachotoxin (BTX) has been shown to induce a time- and concentration-dependent depolarization of a vesicular preparation from guinea pig cerebral cortex. The K0.5 for depolarization by BTX was 0.011 microM at 30 min. Membrane potential was determined by the equilibrium distribution of [3H]triphenylmethylphosphonium ion. A series of seven local anesthetics was shown to inhibit BTX-induced depolarization competitively with Ki values ranging from 0.9 microM for dibucaine to 780 microM for lidocaine ethiodide. The specific binding of labeled batrachotoxinin-A 20 alpha-benzoate ([3H]BTX-B) to voltage-sensitive channels in vesicular preparations from mouse cerebral cortex in the presence of scorpion venom was measured and found to yield a range of Kd values from 25 to 30 nM and Bmax values of 0.5 and 1.0 pmole/mg of protein; the same preparation from guinea pig cerebral cortex was found to yield Kd values from 13 to 56 nM and Bmax values of 0.8-2.2 pmoles/mg of protein. A series of 14 local anesthetics was shown to inhibit the specific binding of [3H]BTX-B with Ki values ranging from 0.6 microM for dibucaine to 400 microM for benzocaine. The rank order of potency of the local anesthetics as antagonists of [3H]BTX-B binding was as follows: dibucaine greater than tetracaine greater than bupivacaine greater than diphenhydramine greater than piperocaine greater than cocaine greater than procaine greater than lidocaine greater than benzocaine. The quaternary local anesthetic dimethyl-di(phenylcarbamoylmethyl)ammonium chloride was comparable in potency to tetracaine. The rank order and relative potency of the local anesthetics tested in both paradigms were similar with the exception of lidocaine ethiodide, which was 18 times more potent as an inhibitor of binding of [3H]BTX-B than it was as an inhibitor of BTX-elicited depolarization.

Anesthetics, Local↗