Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Quinolinium Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed2001

Noninvasive measurement of chloride concentration in rat olfactory receptor cells with use of a fluorescent dye.

Inwardly directed Ca(2+)-dependent chloride currents are thought to prolong and boost the odorant-induced transient receptor currents in olfactory cilia. Cl(-) inward current, of course, requires a sufficiently high intracellular Cl(-) concentration ([Cl(-)](i)). In previous measurements using a fluorescent Cl(-) probe, N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE), [Cl(-)](i) of newt olfactory cells was estimated to be only 40 mM. This low value led us to reexamine the [Cl(-)](i) by an improved procedure. When isolated rat olfactory neurons were bathed in Tyrode's solution (150 mM Cl(-)) at room temperature, the [Cl(-)] was 81.5 +/- 13.5 mM (mean +/- SE) in the tip of the dendrite (olfactory knob) and 81.8 +/- 10.2 mM (mean +/- SE) in the soma. The corresponding Cl(-) equilibrium potentials were -15.4 and -15.3 mV, respectively. Therefore, at resting potentials in the range of -90 to -50 mV, Cl(-) currents are predicted to be inward and capable of contributing to the depolarization induced by odorants. Yet, if the cell was depolarized beyond -15 mV, somal Cl(-) currents would be outward and facilitate repolarization during excitation. The measured [Cl(-)] in soma and knob are of interest, because in the cilia the chloride content may be expected to equilibrate with that of the knob in the resting state. They provide a starting point for the decrease in ciliary [Cl(-)] predicted to occur during transduction.

Animals↗
PubMed1993

Stimulation of Cl permeability in colonic crypts of Lieberkühn measured with a fluorescent indicator.

Crypts of Lieberkühn were isolated from rabbit distal colon and the halide-sensitive dye 6-methoxy-N-[3-sulfopropyl]quinolinium was used to monitor changes in cell Cl by fluorescence microscopy. Distal colon from rabbits actively secretes Cl and K when stimulated with prostaglandin (PG) E2 but secretes only K in response to epinephrine. The secretagogues PGE2 and epinephrine each produced transient decreases of the apparent cell Cl concentration in about one-half of the crypt cells. Permeability to Cl was assessed by brief substitutions with gluconate or Br in the bath. After stimulation of secretion by PGE2 or epinephrine, Cl efflux and Br influx were increased but only in the cells that exhibited the decrease in cell Cl at the onset of stimulation. Although Cl efflux during gluconate substitution was stimulated similarly with either PGE2 or epinephrine, epinephrine stimulation led to a lower apparent Cl concentration after 2 min of gluconate substitution. Together these results support the concept that a particular epithelial cell type in the crypts responds to secretagogues and that the Cl permeability pathways differ between the secretory states induced by PGE2 and epinephrine.

Animals↗
PubMed2002

P2X purinergic receptor channel expression and function in bovine aortic endothelium.

We examined bovine aortic endothelial cells (BAECs) for the functional expression of P2X receptors, the ATP-gated cation channels. We identified the P2X subtypes present in BAECs using RT-PCR. mRNA was present for only three of seven family members: P2X4, P2X5, and P2X7. We then characterized agonist-activated currents in whole cell and outside-out patch recordings using 2-methyl-thio-ATP (MeSATP) as a P2X4 and P2X5 receptor agonist and 2',3'-O-(4-benzoylbenzoyl)ATP (BzATP) as a P2X7 receptor agonist. MeSATP (10-20 microM) produced current with characteristics of P2X4 receptors. The current was an inwardly rectifying current, reversed near 0 mV, slowly desensitized, was not blocked by suramin (300 microM) or reactive blue (60 microM), and had a single channel conductance of 36 pS. BzATP (10-100 microM), on the other hand, activated a 9-pS channel with sustained activity in the continued presence of the agonist. BzATP-activated current was blocked by reactive blue (60 microM) and by suramin (approximately 50% block at 300 microM). We confirmed, by immunocytochemistry, the presence of P2X4 and P2X7 protein. The agonists failed, however, to induce significant uptake of the large molecule YO-PRO, indicating the lack of pore development that has been demonstrated for P2X7 and P2X4 in response to agonist in some cell types.

Adenosine Triphosphate↗
PubMed1992

Differential effects of WEB 2086 and SRI 63-441 on TNF-alpha-induced alterations in cardiopulmonary function.

We hypothesized that platelet-activating factor (PAF) and cyclooxygenase products might be important mediators of the cardiopulmonary effects induced by tumor necrosis factor (TNF-alpha) in anesthetized pigs. A 6-h infusion of human recombinant TNF-alpha caused hypoxemia, leukopenia, thrombocytopenia, decreased cardiac index (CI), increased pulmonary vascular resistance (PVR) and increased mean pulmonary arterial (Ppa) and intratracheal (Pt) pressures. Administration of the PAF receptor antagonist SRI 63-441 or indomethacin blocked the early (0.25-0.5 h) and attenuated the later increases in PVR and Ppa; indomethacin also attenuated the increase in Pt and hypoxemia associated with TNF-alpha infusion. WEB 2086 did not attenuate the TNF-alpha-induced alterations in CI, PVR, Pt, or PaO2. The in vivo specificity of SRI 63-441 and WEB 2086 was tested by infusing exogenous PAF, prostaglandin (PG) F2 alpha, U-46619 [thromboxane (Tx)A2 receptor mimetic], or arachidonic acid (AA) before and during administration of SRI 63-441 or WEB 2086. Both antagonists blocked the cardiopulmonary effects induced by exogenous PAF. SRI 63-441, but not WEB 2086, significantly attenuated the increased PVR caused by PGF2 alpha, U-46619, and AA. We conclude that SRI 63-441 is a less specific PAF receptor antagonist in vivo compared with WEB 2086 and that cyclooxygenase products, but not PAF, contribute significantly to the cardiopulmonary responses induced by exogenously infused TNF-alpha in pigs.

Animals↗
PubMed1994

Use of MQAE for measurement of intracellular [Cl-] in cultured aortic smooth muscle cells.

A novel fluorescent indicator, N-[ethoxycarbonylmethyl]-6-methoxy-quinolinium bromide (MQAE), was used to measure intracellular chloride concentration ([Cl-]i) in primary cultures of rat aortic smooth muscle cells (VSMC). The hydrolytic and fluorescent properties of the dye were characterized. The intracellular Stern-Volmer constant was calculated to be 25 M-1. Cl- efflux curves were characteristic of saturation-type kinetics, with an apparent Michaelis-Menten constant value of 11 +/- 4.8 (SD) mM, a maximum velocity of 0.038 +/- 0.021 mM/s, and a half time (t1/2) of 9.0 +/- 3.7 min. The average efflux rate in the first 10 min (0.023 +/- 0.004 mM/s) was reduced in the presence of either 130 microM 4,4'-diisothiocyanato-dihydrostilbene-2,2'-disulfonic acid (H2DIDS) (0.014 +/- 0.006, P = 0.02) or 40 microM furosemide (0.017 +/- 0.004, P = 0.04). Restoration of physiological extracellular chloride concentration ([Cl-]o) after zero Cl- resulted in net Cl- influx with a t1/2 of 3.6 +/- 1.0 min. The initial Cl- influx rate was reduced after exposure to furosemide, from 0.069 +/- 0.006 to 0.046 +/- 0.008 mM/s, P < 0.002, and was reduced after exposure to H2DIDS from 0.102 +/- 0.013 to 0.033 +/- 0.003 mM/s, P < 0.001. Furosemide reduced the steady-state [Cl-]i from 31.6 +/- 3.2 to 26.1 +/- 2.4 mM, P < 0.01, whereas H2DIDS had little effect on [Cl-]i. Our results demonstrate that MQAE can be used to measure [Cl-]i in primary cultures of VSMC.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

Overexpression of R domain eliminates cAMP-stimulated Cl- secretion in 9/HTEo- cells in culture.

The intracellular hydrophilic region of the cystic fibrosis transmembrane conductance regulator (CFTR), the R domain, has been postulated to be a regulator of the Cl-channel. Under basal conditions R blocks the channel, but when phosphorylated, R undergoes conformational change to open the channel. Overexpression of R in 9/HTEo- cells, a human tracheal epithelial cell line with adenosine 3',5' -cyclic monophosphate (cAMP)-regulated Cl- conductance due to CFTR, caused reduced basal Cl- conductance and elimination of its response to isoproterenol, but ionomycin-stimulated Cl- efflux was preserved. Cells which overexpressed R showed no downregulation of endogenous CFTR mRNA and had normal cAMP production and protein kinase A (PKA) activity, so R did not act at these levels. Although the precise mechanism by which R affects CFTR conductance is undetermined, these cell lines could be useful in separating the cell biological consequences of impaired Cl- transport from those of mutant CFTR per se.

Base Sequence↗
PubMed1988

Renal brush-border chloride transport mechanisms characterized using a fluorescent indicator.

Cl transport mechanisms in brush-border membrane vesicles (BBMV) isolated from rabbit renal cortex were characterized using the Cl-sensitive fluorescent indicator 6-methoxy-N-[3-sulfopropyl]quinolinium (SPQ). In control experiments using 36Cl, SPQ did not itself alter rates for Cl transport. Cl fluxes (JCl) in nanomoles per second per milligram vesicle protein in response to gradients of Cl and other ions were calculated from the SPQ fluorescence time course, fluorescence vs. [Cl] calibration, and BBMV glucose space (microliter/mg protein). For a 50 mM inwardly directed Cl gradient in BBMV (voltage and pH clamped) JCl was 0.26 +/- 0.01 nmol.s-1.mg-1 (mean +/- SD, 4 vesicle preparations). JCl was not altered by a 50 mM inwardly directed Na gradient (0.25 +/- 0.01 nmol.s-1.mg-1) but increased to 0.52 +/- 0.04 nmol.s-1.mg-1 when driven by a 1.5 pH unit inwardly directed proton gradient. The pH driven increase in JCl was blocked by H2DIDS (100 microM, JCl = 0.38 +/- 0.02 nmol.s-1.mg-1). In the absence of a gradient, JCl increased by 64 +/- 4% in the presence of 1 mM formate on both sides of the membrane; the increase was blocked by H2DIDS. JCl increased to 0.38 +/- 0.02 nmol.s-1.mg-1 for a 60-mV K valinomycin diffusion potential (internal positive); the increase was inhibited by the Cl channel blocker diphenylamine-2-carboxylate (DPC, 100 microM, JCl = 0.26 +/- 0.03 nmol.s-1.mg-1). Br and I transport was also blocked by DPC.(ABSTRACT TRUNCATED AT 250 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

Calcium-activated chloride currents in primary cultures of rabbit distal convoluted tubule.

Chloride (Cl-) conductances were studied in primary cultures of rabbit distal convoluted tubule (very early distal "bright" convoluted tubule, DCTb) by the whole cell patch-clamp technique. We identified a Cl- current activated by 2 microM extracellular ionomycin. The kinetics of the macroscopic current were time dependent for depolarizing potentials with a slow developing component. The steady state current presented outward rectification, and the ion selectivity sequence was I- > Br- > > Cl > glutamate. The current was inhibited by 0.1 mM 5-nitro-2-(3-phenylpropyl-amino)benzoic acid, 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, and 1 mM diphenylamine-2-carboxylate. To identify the location of the Cl- conductance, 6-methoxy-N-(3-sulfopropyl)quinolinium fluorescence experiments were carried out in confluent cultures developed on collagen-coated permeable filters. Cl- removal from the apical solution induced a Cl- efflux that was stimulated by 10 microM forskolin. Forskolin had no effect on the basolateral Cl- permeability Cl- substitution in the basolateral solution induced an efflux stimulated by 2 microM ionomycin or 50 microM extracellular ATP Ionomycin had no effect on the apical Cl- fluxes. Thus cultured DCTb cells exhibit Ca(2+)-activated Cl- channels located in the basolateral membrane. This Cl- permeability was active at a resting membrane potential and could participate in the Cl- reabsorption across the DCTb in control conditions.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1999

Regulation of cAMP-dependent chloride channels in DC1 immortalized rabbit distal tubule cells in culture.

Cl- conductances were studied in an immortalized cell line (DC1) derived from rabbit distal bright convoluted tubule (DCTb). The DC1 clone was obtained after transfection of primary cultures of DCTb with pSV3 neo. RT-PCR experiments showed the presence of cystic fibrosis transmembrane conductance regulator (CFTR) mRNA in the DC1 cell line. Using the whole cell patch-clamp technique, we recorded a linear Cl- conductance activated by forskolin (FK). This conductance was insensitive to DIDS and corresponded to a CFTR-like channel conductance. Fluorescence experiments with 6-methoxy-1-(3-sulfonatopropyl)quinolinium (SPQ) showed that FK induced an increase in Cl- efflux and influx in DC1 cells similar to that observed in cultured DCTb cells. 125I- efflux experiments performed on DC1 cells grown on collagen-coated filters showed that exposure of the monolayer to FK led to an increased 125I- loss through the apical membrane only. The addition of 10 microM adenosine activated a linear conductance identical to that recorded with FK and corresponding to the CFTR-like conductance. This conductance was also activated by 5'-(N-ethylcarboxamido)adenosine and CGS-21680 and inhibited in the presence of 8-cyclopentyl-1, 3-diproxylxanthine (DPCPX). This Cl- conductance could also be activated by guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS). The addition of protein kinase A (PKA) inhibitor to the pipette solution inhibited the development of the current activated by CGS-21680. Finally, 125I- efflux showed that adenosine induced an apical efflux mediated through basolateral A2 receptors. Overall, the data show that the DC1 cell line expressed an apical CFTR Cl- conductance that could be activated by adenosine via A2A receptors located in the basolateral membrane and involving G protein and PKA pathways.

Adenosine↗
PubMed2000

A functional angiotensin II receptor-GFP fusion protein: evidence for agonist-dependent nuclear translocation.

We constructed an expression vector for a fusion protein [ANG II type 1a receptor-green fluorescent protein (AT(1a)R-GFP)] consisting of enhanced GFP attached to the COOH terminus of the rat AT(1a)R. Chinese hamster ovary (CHO) cells transfected with AT(1a)R-GFP demonstrated specific, high-affinity (125)I-labeled ANG II binding (IC(50) 21 nM). ANG II exposure stimulated sodium-proton exchange and cytoplasmic calcium release to a similar extent in cells transfected with AT(1a)R or AT(1a)R-GFP; these responses were desensitized by prior exposure to ANG II and were sensitive to the AT(1)R blocker losartan. ANG II-driven internalization of AT(1a)R-GFP in transfected CHO cells was demonstrated both by radioligand binding and by laser scanning confocal microscopy. Colocalization of GFP fluorescence with that of the nuclear stain TOTO-3 in confocal images was increased more than twofold after 1 h of ANG II exposure. We conclude that AT(1a)R-GFP exhibits similar pharmacological behavior to that of the native AT(1a)R. Our observations also support previous evidence for the presence of AT(1a)R in the nucleus and suggest that the density of AT(1a)R in the nucleus may be regulated by exposure to its ligand.

Angiotensin II↗
PubMed1988

Platelet-activating factor antagonists increase vascular reactivity in perfused rat lungs.

Platelet-activating factor (PAF) administered to the pulmonary circulation in low dose (nanogram) has vasodilatory properties. Therefore, we investigated whether endogenous PAF plays a role in the control of tone in the pulmonary circulation. The PAF receptor antagonists, SRI 63-441 (2.6 X 10(-4) M) and L659,989 (1 X 10(-5) M), were the major investigative tools. In isolated perfused rat lungs, both agents caused a persistent increase in base-line perfusion pressure (Ppa), potentiated angiotensin II (ANG II) vasoconstriction, and potentiated hypoxic vasoconstriction (HPV). This potentiation of ANG II and HPV was found to be independent of circulating blood elements. Vasodilation in the presence of PAF blockade was also impaired. The combination of cyclooxygenase inhibition and PAF receptor blockade had an additive effect on ANG II vasoconstriction but did not cause more potentiation of HPV than achieved with PAF antagonism alone. In vivo, SRI 63-441 (10 mg/kg) caused only a transient increase in base-line Ppa without altering ANG II and hypoxic vasoconstriction. These findings support a vasodilatory role for endogenous PAF in the pulmonary circulation.

Angiotensin II↗
PubMed1988

Effects of platelet-activating factor antagonist SRI 63-441 on endotoxemia in sheep.

We investigated whether platelet-activating factor (PAF) mediates endotoxin-induced systemic and pulmonary vascular derangements by studying the effects of a selective PAF receptor antagonist, SRI 63-441, during endotoxemia in sheep. Endotoxin infusion (1.3 micrograms/kg over 0.5 h) caused a rapid, transient rise in pulmonary arterial pressure (Ppa) from 16 +/- 3 to 36 +/- 10 mmHg (P less than 0.001) and pulmonary vascular resistance (PVR) from 187 +/- 84 to 682 +/- 340 dyn.s.cm-5 (P less than 0.05) at 0.5 h, followed by a persistent elevation in Ppa to 22 +/- 3 mmHg and in PVR to 522 +/- 285 dyn.s.cm-5 at 5 h in anesthetized sheep. Arterial PO2 (PaO2) decreased from 341 +/- 79 to 198 +/- 97 (P less than 0.01) and 202 +/- 161 Torr at 0.5 and 5 h, respectively (inspired O2 fraction = 1.0). SRI 63-441, 20 mg.kg-1.h-1 infused for 5 h, blocked the early rise in Ppa and PVR and fall in PaO2, but had no effect on the late phase pulmonary hypertension or hypoxemia. Endotoxin caused a gradual decrease in mean aortic pressure, which was unaffected by SRI 63-441. Infusion of SRI 63-441 alone caused no hemodynamic alterations. In follow-up studies, endotoxin caused an increase in lung lymph flow (QL) from 3.8 +/- 1.1 to 14.1 +/- 8.0 (P less than 0.05) and 12.7 +/- 8.6 ml/h at 1 and 4 h, respectively. SRI 63-441 abolished the early and attenuated the late increase in QL.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Pulmonary vascular reactivity: effect of PAF and PAF antagonists.

We investigated the effects of two different platelet-activating factor (PAF) antagonists, SRI 63-441 and WEB 2086, on PAF-, angiotensin II-, and hypoxia-induced vasoconstrictions in isolated rat lungs perfused with a physiological salt solution. Bolus injection of PAF (0.5 micrograms) increased pulmonary arterial and microvascular pressures and caused lung edema. Both SRI 63-441, a PAF-analogue antagonist, and WEB 2086, a thienotriazolodiazepine structurally unrelated to PAF, completely blocked PAF-induced vasoconstriction and lung edema at 10(-5) M. At a lower concentration (10(-6) M), WEB 2086 was more effective than SRI 63-441. WEB 2086 also blocked the pulmonary vasodilation induced by low-dose PAF (15 ng) in blood-perfused lungs preconstricted with hypoxia. SRI 63-441 and CV 3988 (another PAF analogue antagonist), but not WEB 2086, caused acute pulmonary vasoconstriction at 10(-5) M and severe lung edema at a higher concentration (10(-4) M). PAF-induced but not SRI- or CV-induced pulmonary vasoconstriction and edema were inhibited by WEB 2086. In addition, SRI 63-441 potentiated angiotensin II- and hypoxia-induced vasoconstrictions. This effect of SRI 63-441 is not due to PAF receptor blockade because 1) addition of PAF (1.6 nM) to the perfusate likewise potentiated angiotensin II-induced vasoconstriction and 2) WEB 2086 did not cause a similar response. We conclude that both SRI 63-441 and WEB 2086 are effective inhibitors of PAF actions in the rat pulmonary circulation. However, antagonists with structures analogous to PAF (SRI 63-441 and CV 3988) can have significant pulmonary vasoactive side effects.

Angiotensin II↗
PubMed2004

Firing properties and connectivity of neurons in the rat lateral central nucleus of the amygdala.

Using whole cell recordings from acute slices of the rat amygdala, we have examined the physiological properties of and synaptic connectivity to neurons in the lateral sector of the central amygdala (CeA). Based on their response to depolarizing current injections, CeA neurons could be divided into three types. Adapting neurons fired action potentials at the start of the current injections at high frequency and then showed complete spike-frequency adaptation with only six to seven action potentials evoked with suprathreshold current injections. Late-firing neurons fired action potentials with a prolonged delay at threshold but then discharged continuously with larger current injections. Repetitive firers discharged at the start of the current injection at threshold and then discharged continuously with larger current injections. All three cells showed prolonged afterhyperpolarizations (AHPs) that followed trains of action potentials. The AHP was longer lasting with a larger slow component in adapting neurons. The AHP in all cell types contained a fast component that was inhibited by the SK channel blocker UCL1848. The slow component, not blocked by UCL1848, was blocked by isoprenaline and was significantly larger in adapting neurons. Blockade of SK channels increased the discharge frequency in late firers and regular-spiking neurons but had no effect on adapting neurons. Blockade of the slow AHP with isoprenaline had no effect on any cell type. All cells received a mixed glutamatergic and GABAergic input from a medial pathway. Electrical stimulation of the lateral (LA) and basolateral (BLA) nuclei evoked a large monosynaptic glutamatergic response followed by a disynaptic inhibitory postsynaptic potential. Activation of neurons in the LA and BLA by puffer application of glutamate evoked a small monosynaptic response in 13 of 55 CeA neurons. Local application of glutamate to the CeL evoked a GABAergic response in all cells. These results show that at least three types of neurons are present in the CeA that can be distinguished on their firing properties. The firing frequency of two of these cell types is determined by activation of SK channels. Cells receive a small input from the LA and BLA but may receive inputs that course through these nuclei en route to the CeA.

Action Potentials↗
PubMed2005

Shift of intracellular chloride concentration in ganglion and amacrine cells of developing mouse retina.

GABA and glycine provide excitatory action during early development: they depolarize neurons and increase intracellular calcium concentration. As neurons mature, GABA and glycine become inhibitory. This switch from excitation to inhibition is thought to result from a shift of intracellular chloride concentration ([Cl-]i) from high to low, but in retina, measurements of [Cl-]i or chloride equilibrium potential (ECl) during development have not been made. Using the developing mouse retina, we systematically measured [Cl-]i in parallel with GABA's actions on calcium and chloride. In ganglion and amacrine cells, fura-2 imaging showed that before postnatal day (P) 6, exogenous GABA, acting via ionotropic GABA receptors, evoked calcium rise, which persisted in HCO3- -free buffer but was blocked with 0 extracellular calcium. After P6, GABA switched to inhibiting spontaneous calcium transients. Concomitant with this switch we observed the following: 6-methoxy-N-ethylquinolinium iodide (MEQ) chloride imaging showed that GABA caused an efflux of chloride before P6 and an influx afterward; gramicidin-perforated-patch recordings showed that the reversal potential for GABA decreased from -45 mV, near threshold for voltage-activated calcium channel, to -60 mV, near resting potential; MEQ imaging showed that [Cl-]i shifted steeply around P6 from 29 to 14 mM, corresponding to a decline of ECl from -39 to -58 mV. We also show that GABAergic amacrine cells became stratified by P4, potentially allowing GABA's excitatory action to shape circuit connectivity. Our results support the hypothesis that a shift from high [Cl-]i to low causes GABA to switch from excitatory to inhibitory.

Action Potentials↗
PubMed2002

K+ currents generated by NMDA receptor activation in rat hippocampal pyramidal neurons.

Long lasting outward currents mediated by Ca2+-activated K+ channels can be induced by Ca2+ influx through N-methyl-D-aspartate (NMDA)-receptor channels in voltage-clamped hippocampal pyramidal neurons. Using specific inhibitors, we have attempted to identify the channels that underlie these outward currents. At a holding potential of -50 mV, applications of 1 mM NMDA to the soma of cultured hippocampal pyramidal neurons induced the expected inward currents. In 44% of cells tested, these were followed by outward currents (average amplitude 60 +/- 7 pA) that peaked 2.5 s after the initiation of the inward NMDA currents and decayed with a time constant of 1.4 s. In 43% of those cells exhibiting an outward current, SK channel inhibitors, UCL 1848 (100 nM) and apamin (100 nM) abolished the outward current. In the remainder of the cells, the outward currents were either insensitive or only partly inhibited (44 +/- 4%) by 100 nM UCL 1848. In these cells, the outward currents were reduced by the slow afterhyperpolarization (sAHP) inhibitors, muscarine (3 microM; 43 +/- 9%), UCL 1880 (3 microM; 34 +/- 10%), and UCL 2027 (3 microM; 57 +/- 6%). Neither the BK channel inhibitor, charybdotoxin (100 nM), nor the Na+/K+ ATPase inhibitor, ouabain (100 microM), reduced these outward currents. Irrespective of the pharmacology, the time course of the outward current did not differ. Interestingly, no correlation was observed between the presence of a slow apamin-insensitive afterhyperpolarization and an outward current insensitive to SK channel blockers following NMDA-receptor activation. It is concluded that an NMDA-mediated rise in [Ca2+]i can result in the activation of apamin-sensitive SK channels and of the channels that underlie the sAHP. The activation of these channels may, however, depend on their location relative to NMDA receptors as well as on the spatial Ca2+ buffering within individual neurons.

Action Potentials↗
PubMed2005

Induction of apoptosis of human tumor cells by a 4,9-diazapyrenium derivative and its affects on topoisomerase-II action.

BACKGROUND: 5,10-Diphenyl-4,9-dimethyl-4,9-diazapyrenium hydrogensulfate (FDAP) is a newly synthesized DNA intercalator with strong antiproliferative activity against various human tumor cells. In this study, FDAP's potential to induce apoptosis in human pancreatic (MIAPaCa-2) and colon (Caco-2) carcinoma cells and its effects on topoisomerase-II activity were investigated. METHODS: Cytotoxicity was analyzed using the MTT assay. Antiproliferative activity was measured using a radioactive precursor incorporation assay. DNA fragmentation was analyzed by agarose gel electrophoresis. Apoptosis was detected using annexin-V fluorescein. To screen the topoisomerase-II-targeted effects of FDAP, cell-free assays were used. RESULTS: FDAP at concentrations of 10 and 1 microM caused a strong cytotoxic effect on MIAPaCa-2 cells, but only a slight effect on WI38 cell viability. Inhibition of the DNA, RNA and protein synthesis of the treated tumor cells was dependent on cell type. The DNA of the treated MIAPaCa-2 cells was fragmented. Phosphatidylserine externalization was detected in both tumor cell lines investigated. FDAP caused generation of DNA strand breaks due to interaction with human topoisomerase-IIalpha. CONCLUSION: 1 microM FDAP caused apoptotic cell death of treated tumor cells. FDAP stimulated topoisomerase-II-mediated DNA cleavage and could be considered a topoisomerase-II poison.

Apoptosis↗
PubMed1978

Initial studies on the disposition of quinolinium dibromide (NSC-176319) in mice and rats.

The disposition of quinolinium dibromide (QdB), a highly active agent against murine L1210 leukemia was studied using 14C-labeled drug. Excretion of radioactivity was slow, with only 10 and 16% of the dose eliminated in the urine and 19 and 24% in the feces, 96h after intraperitoneal administration of QdB to mice and rats, respectively. Plasma levels of 14C were low and decreased with time, whereas tissue concentrations were high and remained elevated. Differences in tissue concentrations observed in the rat 96 h following intravenous and intraperitoneal dosing could be explained by QdB binding. A strong association between QdB and DNA was indicated by the effect of DNA on the absorption spectrum and Sephadex G-200 elution profile of QdB.

Animals↗