Tamoxifen and raloxifene modulate gap junction coupling during early phases of retinoic acid-dependent neuronal differentiation of NTera2/D1 cells.

Gap junctions (GJ) represent a cellular communication system known to influence neuronal differentiation and survival. To assess a putative role of this system for neural effects of tamoxifen (TAM) and raloxifene (RAL), we used the human teratocarcinoma cell line NTera2/D1, retinoic acid (RA)-dependent neuronal differentiation of which is regulated by gap junctions formed of connexin43 (Cx43). As demonstrated by Western blot analysis, concentrations above 1 µmol/l for TAM, and 0.

DNA taxonomy, cryptic speciation and diversification of the Neotropical-African liverwort, Marchesinia brachiata (Lejeuneaceae, Porellales).

The Neotropical-African liverwort Marchesinia brachiata has long been regarded as a polymorphic species. This hypothesis is examined using a dataset including sequences of the nuclear internal transcribed spacer region and the plastidic trnL-trnF region of 39 Marchesinia accessions. Maximum parsimony, maximum likelihood and Bayesian analyses indicate that Marchesinia robusta is nested within M.

Bodipy-FL-verapamil: a fluorescent probe for the study of multidrug resistance proteins.

Most of the substances used as fluorescent probes to study drug transport and the effect of efflux blockers in multidrug resistant cells have many drawbacks, such as toxicity, unspecific background, accumulation in mitochondria. New fluorescent compounds, among which Bodipy-FL-verapamil (BV), have been therefore proposed as more useful tools. The uptake of BV has been evaluated by cytofluorimetry and fluorescence microscopy using cell lines that overexpress P-glycoprotein (P388/ADR and LLC-PK(1)/ADR) or MRP (multidrug resistance-related protein) (PANC-1) and clinical specimens from patients.

Expression and function of P-glycoprotein and absence of multidrug resistance-related protein in rat and beige mouse peritoneal mast cells.

To clarify the function of the multidrug transporter P-glycoprotein in mast cells we used the green fluorescent compound Bodipy-FL-verapamil, which is a substrate of P-glycoprotein. This compound is also transported by Multidrug Resistance-related Protein (MRP), another membrane transport protein expressed in many tumour resistant cells as well as in normal cells. When rat peritoneal mast cells were incubated with Bodipy-verapamil, a rapid uptake of this compound was observed.

Biochemical and microscopic evidence for the internalization of drug-containing mast cell granules by macrophages and smooth muscle cells.

During mast cell degranulation the soluble component of the granule is released into extracellular fluid, whereas two neutral proteases and heparin proteoglycans form the extracellular granule remnants. These structures are negatively charged and bind with high affinity LDL and other basic molecules. In this study we show that granule remnants expelled into extracellular fluid are able to bind the aminoglycoside antibiotic gentamicin and the anticancer agent doxorubicin in a dose-dependent manner.

Cytofluorimetric analysis of a renal tubular cell line and its resistant counterpart.

P-glycoprotein (P-gp) and multidrug resistance related protein (MRP) overexpression is often responsible of the development of multidrug resistance in cancer therapy. These proteins are also expressed in normal tissues, where their physiological role is related to the extrusion of endogenous toxins or to secretory function in liver and kidney. The LLC-PK1 cell line is derived from normal pig proximal renal tubule and physiologically expresses low levels of P-gp and MRP.

Kinetics of doxorubicin handling in the LLC-PK1 kidney epithelial cell line is mediated by both vesicle formation and P-glycoprotein drug transport.

The subcellular distribution of doxorubicin was evaluated in living non-fixed LLC-PK1 cells, which maintain the structural and functional characteristics of the kidney proximal tubule epithelium and also express P-glycoprotein. After 10 min incubation, doxorubicin fluorescence was detectable in the nucleus. The intensity of nuclear fluorescence progressively increased, reaching the maximum at the end of the first hour.

Endocytosis of gentamicin in a proximal tubular renal cell line.

The mechanisms by which aminoglycosides are accumulated in renal proximal tubular cells remain unclear. Adsorptive mediated endocytosis, via a common pathway for cationic proteins, or receptor endocytosis, mediated by the glycoprotein 330/megalin, have been proposed to be involved in gentamicin transport in renal cells. We used the LLC-PK1 cell line, derived from the pig proximal tubule, to explore further the regulation of gentamicin endocytosis in these cells and to determine the role of clathrin mediated endocytosis and G proteins in this function.

Adriamycin induces exocytosis in rat and beige mouse peritoneal mast cells: an ultrastructural, morphometric and biochemical study.

The process of exocytosis was studied in rat and beige mouse peritoneal mast cells stimulated by adriamycin (ADR) at 37 degrees C and 22 degrees C. ADR induces a non cytotoxic histamine release that is followed by a significant uptake of the drug. Examination was performed by transmission electron microscopy and, at the same time, histamine release and ADR uptake were measured by spectrofluorimetry.

Transport of doxorubicin in mast cell granules and the effect of the calcium antagonist verapamil.

P-glycoprotein has been identified in mast cells stabilized in culture as well as in rat peritoneal mast cells, and is primarily concentrated on the granular membrane. This study aimed to define the role of this protein in the transport and accumulation of doxorubicin in mast cell granules and in its histamine releasing effect. The reverting agent verapamil, that is a substrate for P-glycoprotein, inhibited doxorubicin uptake in intact mast cells in a dose and time dependent manner, but had no effect on the exocytotic action of the antineoplastic drug.

Handling of doxorubicin by the LLC-PK1 kidney epithelial cell line.

The characteristics of doxorubicin handling have been studied in the cultured kidney epithelial cell line LLC-PK1, which has structure and function similar to those of renal tubular cells and expresses P-glycoprotein. The uptake of doxorubicin by LLC-PK1 cells was time dependent, reaching a steady state at about 4 hr, and reduced at low temperature; the initial uptake was saturable. The efflux of doxorubicin from LLC-PK1 cells was also temperature dependent but, even at 37 degrees C, a significant percentage of the drug remained associated with the cells after 180 min, which suggests a strong cellular binding, and the fluorescence microscopy revealed that the drug was concentrated in intracellular organelles.

Stimulation of rat peritoneal mast cells induces phagocytosis of adriamycin by rat peritoneal macrophages.

Rat and beige mouse peritoneal mast cells, induced to exocytose with the antineoplastic agent adriamycin, extrude their granule remnants in the extracellular medium. These granules are loaded with the fluorescent drug adriamycin and exhibit intense yellow-reddish fluorescent staining. Granules extruded from mast cells were ultimately phagocytosed and could be observed inside the macrophages by fluorescence microscopy.

Adriamycin binds to the matrix of secretory granules during mast cell exocytosis.

The antineoplastic drug adriamycin induces exocytosis in rat peritoneal mast cells followed by a significant uptake of the drug into the secretory granules. The drug is fluorescent, allowing visualization of its accumulation and binding to mast cell granules by fluorescence microscopy. At the same time, the well known inorganic dye ruthenium red was used as a probe because of its great affinity for heparin in the mast cell secretory granules as visualized by bright field microscopy.

Adriamycin-induced histamine release from heart tissue in vitro.

It has been proven that the anthracyclines induce an important, noncytotoxic histamine release from rat peritoneal mast cells. As mast cells derived from different tissues exhibit marked heterogeneity, the effect of Adriamycin in comparison with other antineoplastic agents was tested on fragments of the right heart auricle, which contain a great number of mast cells. In this experimental model, Adriamycin induced a dose-dependent histamine release that was significantly limited by the antiexocytotic drug sodium cromoglycate.

Binding of aminoglycoside antibiotics by degranulating mast cells.

The aminoglycoside antibiotics are polycationic at physiological pH and hence do not enter most cells. Indeed, when intact mast cells were incubated with gentamicin or tobramycin, extremely low concentrations of the two drugs could be measured. In contrast, when a controlled, specific degranulation of mast cells was induced by treating the cells with compound 48/80, Adriamycin or concanavalin A, a dose-dependent histamine release was observed and a significant increase of the intracellular concentrations of the aminoglycosides resulted.

Optimised method for determination of ticlopidine in serum by high performance liquid chromatography.

In this study we verified whether high performance liquid chromatography with UV detection (HPLC-UV) could be optimised and hence become a useful method for measuring ticlopidine concentrations in patient blood. The extraction step was improved by adding isoamylic alcohol in the extraction mixture, resulting in a better recovery. Moreover, the extraction efficiency was consistently ameliorated by evaporation to dryness of the organic extract; we could therefore utilise a lower (213 nm) wavelength, corresponding to the maximum of absorption, achieving a better sensitivity.

Evidence of an adriamycin binding site in the secretory granules of the mast cell.

Adriamycin induced significant non-cytotoxic histamine release from rat peritoneal mast cells to which the drug showed a very high affinity. The relationship between adriamycin-induced exocytosis and its uptake by purified rat peritoneal mast cells was studied. Adriamycin induced histamine release and was highly concentrated in mast cells at 37 degrees C but not at 0 degrees C.

Effect of lysosomotropic and membrane active substances on adriamycin uptake and histamine release.

It has recently been shown that adriamycin is accumulated in mast cells by an active transport system, which closely resembles the outward transport system of multidrug resistant (MDR) cells. The present study was undertaken in order to test the effect of substances which are known to limit or reverse resistance in MDR cells on adriamycin uptake and histamine release in rat peritoneal mast cells. The lysosomotropic amines chloroquine, nicotine, propranolol, atropine, methylamine, ammonium chloride and quinacrine were only slightly effective at very high concentrations; no effect could be observed with the lysosomotropic amine amantadine.

Uptake of adriamycin by rat and mouse mast cells and correlation with histamine release.

It has been shown recently that anthracyclines induce an important, noncytotoxic histamine release from rat and mouse peritoneal mast cells. In the present study we evaluate if histamine release is related to Adriamycin uptake; in addition the uptake of this antineoplastic drug is studied in other normal or tumor cells. In rat and mouse peritoneal mast cells, Adriamycin-induced histamine release is quantitatively related to its intracellular concentrations.

Interaction of adriamycin with rat and mouse mast cells: histamine release and cellular uptake.

In the present study, we evaluated in mouse and rat mast cells if adriamycin uptake is related to histamine release. In addition, the uptake of the antineoplastic drug and histamine release were studied in other normal and neoplastic cell lines. The effect of sodium cromoglycate was also examined.

Amelioration of 4'-epidoxorubicin-induced cardiotoxicity by sodium cromoglycate.

Epirubicin induces an important noncytotoxic release of histamine from rat peritoneal cells in vitro. This exocytotic response is inhibited by sodium cromoglycate, similarly to that elicited by the classic mast cell secretagogue, compound 48/80. Mast cells obtained from the peritoneal cavities of rats treated with epirubicin in vivo were extensively degranulated; in contrast, samples obtained from rats pretreated with sodium cromoglycate showed normal appearing mast cells.

Adriamycin-induced histamine release from rat peritoneal mast cells: role of free radicals.

The effect of pretreatment with various concentrations of catalase, superoxide-dismutase, D-mannitol, alpha-tocopherol, n-acetylcysteine and reduced glutathione on the release of histamine induced by adriamycin (100 micrograms/ml) on rat peritoneal mast cells was studied. Adriamycin caused an important histamine release in vitro which was not affected by pretreatment with the tested substances. Only n-acetylcysteine, at a very high concentration (1 X 10(-1) M) significantly limited this release.

Dimethyl sulfoxide inhibits histamine release induced by various chemicals.

Dimethyl sulfoxide was found to inhibit histamine release induced by compound 48/80 at concentrations ranging from 0.6 to 10%. At higher concentrations (20 and 40%) the substance caused histamine release by itself.

Inhibitors of adriamycin-induced histamine release in vitro limit adriamycin cardiotoxicity in vivo.

The activity of theophylline and disodium cromoglycate was tested on adriamycin-induced histamine release in vitro and on adriamycin cardiotoxicity in vivo. Both substances significantly inhibited the release of histamine induced by 100 micrograms ml-1 of adriamycin on rat peritoneal cells and produced significant protection against adriamycin-mediated acute and chronic cardiotoxicity in mice. N-acetylcysteine, a free radical scavenger, successfully used in the prevention of the cardiomyopathy, was also found to be an inhibitor of histamine release induced by adriamycin and compound 48/80 on rat peritoneal cells.