sq-23377 and zinc-chloride

The purpose of this study was to determine whether methotrexate modulates bradykinin-induced increase in macromolecular efflux from the in situ oral mucosa and whether this response is mediated by the L-arginine/nitric oxide biosynthetic pathway. Using intravital microscopy, we found that suffusion of methotrexate alone onto the hamster cheek pouch had no significant effects on leaky site formation and increase in clearance of fluorescein isothiocyanate-labeled dextran (molecular mass, 70 kDa). However, methotrexate significantly potentiated bradykinin-induced responses (P < 0.05). These effects were associated with significant increases in nitrites concentration and guanosine 3',5'-cyclic monophosphate-like immunoreactivity in the suffusate and were abrogated by N(G)-nitro-L-arginine methyl ester (L-NAME) but not N(G)-nitro-D-arginine methyl ester (D-NAME). L-Arginine, but not D-arginine, abolished L-NAME-induced responses. ZnCI2 and indomethacin had no significant effects on methotrexate-induced responses. Methotrexate had no significant effects on adenosine- and ionomycin-induced increases in macromolecular efflux. Collectively, these data indicate that methotrexate amplifies bradykinin-induced increase in macromolecular efflux from the in situ oral mucosa in a specific, receptor- and L-arginine/nitric oxide biosynthetic pathway-dependent fashion.

Topics: Adenosine; Animals; Bradykinin; Chlorides; Cricetinae; Enzyme Inhibitors; Indomethacin; Ionomycin; Macromolecular Substances; Male; Mesocricetus; Methotrexate; Mouth Mucosa; NG-Nitroarginine Methyl Ester; Zinc Compounds

We recently described a large, multiple-conductance Cl- channel in excised patches from normal T lymphocytes. The properties of this channel in excised patches are similar to maxi-Cl- channels found in a number of cell types. The voltage dependence in excised patches permitted opening only at nonphysiological voltages, and channel activity was rarely seen in cell-attached patches. In the present study, we show that Cl- channels can be activated in intact cells at physiological temperatures and voltages and that channel properties change after patch excision. Maxi-Cl- channels were reversibly activated in 69% of cell-attached patches when the temperature was above 32 degrees C, whereas fewer than 2% of patches showed activity at room temperature. Upon excision, the same patches displayed large, multiple-conductance Cl- channels with characteristics like those we previously reported for excised patches. After patch excision, warm temperatures were not essential to allow channel activity; 37% (114/308) of inside-out patches had active channels at room temperature. The voltage dependence of the channels was markedly different in cell-attached recordings compared with excised patches. In cell-attached patches, Cl- channels could be open at cell resting potentials in the normal range. Channel activation was not related to changes in intracellular Ca2+ since neither ionomycin nor mitogens activated the channels in cell-attached patches, Ca2+ did not rise in response to warming and the Cl- channel was independent of Ca2+ in inside-out patches. Single-channel currents were blocked by internal or external Zn2+ (100-200 microM), 4-acetamido-4' isothiocyanostilbene-2,2'-disulfonate (SITS, 100-500 microM) and 4,4'-diisothiocyanostilbene 2,2'-disulfonate (DIDS, 100 microM). NPPB (5-nitro-2-(3-phenylpropylamino)-benzoate) reversibly blocked the channels in inside-out patches.

Topics: 4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; 4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; Calcium; Chloride Channels; Chlorides; Electric Conductivity; Humans; Ion Channels; Ionomycin; Membrane Potentials; Membrane Proteins; Nitrobenzoates; T-Lymphocytes; Zinc; Zinc Compounds