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Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolated proximal cells from rabbit kidney were seeded on collagen-coated permeable supports. After 8 days, the cultured cells became organized as a confluent monolayer. The proximal origin of the monolayer was confirmed by enzymatic, immunological, electrical and electron microscopical studies. The epithelia exhibited a morphological polarity that allowed for measurements of effluxes across the apical or the basolateral membranes. 86Rb was used as an isotopic tracer to indicate potassium movements. The 86Rb+ efflux across the basolateral face was 1.93-times that across the apical face, and both effluxes were pH dependent. Apical and basolateral 86Rb+ effluxes increased when the Ca2+ ionophore ionomycin (3 microM) was applied and when monolayers were exposed to a hypotonic medium. A pharmacological study revealed that BaCl2 (5 mM), tetraethylammonium (TEA, 20 mM) and Leiurus quinquestriatus hebraeus scorpion venom (from which charybdotoxin is extracted) abolished both ionomycin and hypotonically-stimulated effluxes, whereas apamin had no significant effect on the hypotonically-stimulated 86Rb+ efflux. This stimulated efflux was also abolished when monolayers were preincubated with pertussis toxin, but did not decrease in a Ca2(+)-free medium.
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PMID:Polarized 86Rb+ effluxes in primary cultures of rabbit kidney proximal cells: role of calcium and hypotonicity. 216 8

1. Neurons with a receptor responded to FMRFamide (Phe-Met-Arg-Phe-NH2) were identified in the ganglion of Aplysia kurodai. Ionic mechanism and channel gating system of the FMRFamide-induced responses were investigated by current clamp and voltage clamp methods. 2. The reversal potential of FMRFamide-induced response exactly coincided with the equilibrium potential for K+. This proved that the response was produced by a specific increase in membrane permeability toward K+, exclusively. 3. The FMRFamide-induced response was not affected by the inhibitors for Ca2(+)-activated K(+)-current, i.e., TEA, apamin, and EGTA. This excluded a possibility that FMRFamide-activated K(+)-channel is a Ca2(+)-activated K(+)-channel. 4. Intracellular injection of pertussis-toxin (PTX) caused no change in either resting potential or conductance, but it irreversibly blocked the FMRFamide-induced outward current within 30 min. Similarly applied cholera toxin (CTX) showed no effect on the FMRF-amide response. 5. Intracellular application of guanosine 5'-0-(2-thiodiphosphate) (GDP beta S) caused no effect on either resting potential or conductance, but it blocked the FMRFamide-induced K(+)-current within 3 min. 6. Intracellular application of guanosine 5'-0-(3-thiotriphosphate) (GTP gamma S) alone induced a slowly developing, irreversible outward current associated with an increase in membrane conductance. However, repetitive applications of FMRFamide immediately after the start of GTP gamma S application markedly facilitated the effect of GTP gamma S on the resting membrane. 7. Intracellular application of either adenylate cyclase inhibitor (3'-deoxyadenosine) or A-kinase inhibitor (H-8) did not affect the FMRFamide-induced response. 8. It was concluded that the FMRFamide-induced K(+)-current is mediated by PTX-sensitive GTP-binding protein Gi, Go or Gk. It was also suggested that the FMRFamide-induced response is produced independently of the changes in intracellular Ca2+ or cyclic AMP.
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PMID:[The gating mechanism of K(+)-channels coupled to the FMRFamide receptor in the ganglion cells of Aplysia]. 255 80

There is evidence to suggest that PGE2 plays an important role in the regulation of vascular smooth muscle tone. To determine the cellular basis of this action, we studied the effect of PGE2 on force in helical muscle strips from rat tail artery. PGE2 evoked a sustained contractile response. The contractile response was concentration-dependent, with an EC50 value of 9.6 microM. Patch-clamp studies were conducted to investigate the effects of PGE2 on K channels in isolated vascular smooth muscle cells from rat tail artery. Current-clamp studies showed that PGE2 (1 microM) depolarized the membrane by 15.9 +/- 1.3 mV. Under voltage-clamp conditions, a voltage-dependent, delayed outward rectifier K current was generated by stepwise depolarization from a holding potential of -80 mV. The current, which was activated at -45 to -40 mV and showed almost no inactivation, was inhibited by 45% using 10 mM TEA. PGE2 inhibited the outward K current in a concentration-dependent manner, with EC50 values of 3.5 microM and 4.9 microM in primary and subcultured cells, respectively. The PGE2 receptor antagonist sodium meclofenamate abolished the PGE2-induced K current inhibition. Furthermore, the intracellular application of guanosine 5'-O(-)[2-thiodiphosphate] (GDP beta S), a G protein inhibitor, and pretreatment of the cells with cholera toxin prevented the PGE2-induced inhibition, whereas application of pertussis toxin did not.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Prostaglandin E2 contracts vascular smooth muscle and inhibits potassium currents in vascular smooth muscle cells of rat tail artery. 747 58

Relative changes in volume were registered in single cells by using a microspectrofluorometric equipment and the fluorescent probe fura-2/AM, excited at its isosbestic point. At this wavelength the probe is ion-insensitive and the fluorescent signals emitted is dependent on variations in the concentration of the dye. Variations in cell volume thus lead to changes in fluorescence intensity as the probe concentration is changed in the lightened delimited zone selected for each cell. When changing the excitation wavelength Ca2+ transients can be recorded. Glutamate (Glu) induced swelling of type I astroglial cells in primary culture and a parallel intracellular Ca2+ increase was obtained. A Glu induced swelling was obtained even after blockade of the Glu ionotropic receptors with NBXQ, suggesting that activation of ionotropic receptors might not be necessary for swelling to occur. On the other hand, blockade of the Glu carrier, or of pertussis toxin sensitive G-proteins reduced the Glu induced swelling. Blockade of Ba2+ or TEA sensitive K+ channels completely blocked the Glu induced swelling as did also blockade with furosemide of the Na+/K+/Cl- co-transporter. Glu induced swelling occurred in parallel with intracellular Ca2+ transients but extracellular Ca2+ did not seem necessary for swelling to occur.
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PMID:Mechanisms of glutamate induced swelling in astroglial cells. 797 21

1. We investigated the effects of histamine on membrane currents and contractile state of isolated guinea-pig tracheal myocytes using perforated patch and whole-cell recording techniques. The effects of histamine were compared to those of acetylcholine (ACh) and caffeine. 2. During voltage clamp (Vhold = -60 mV), histamine elicited contraction and an inward current (Ihist) which was often followed by current oscillations. Ihist had a reversal potential (Vrev) of -9 +/- 3 mV. 3. Ihist was dependent on the Cl- gradient and was antagonized by the Cl- channel blocker niflumic acid. Vrev was more positive (+2 +/- 1 mV) when K(+)-selective currents were blocked by Cs+ and TEA. When all external Na+ was replaced with N-methyl-D-glucamine, there was a small reduction in the amplitude of Ihist. 4. The histamine-induced current was similar to that elicited by ACh and by caffeine with respect to time course, amplitude, and current-voltage relationship. Responses to histamine and to ACh were non-additive, consistent with a convergence of histaminergic and cholinergic signalling pathways. Ihist was antagonized by the H1 histaminergic receptor antagonist astemizole, but not by atropine. 5. When recorded using the perforated patch configuration, Ihist could be elicited repeatedly for more than 30 min. When cells were studied in the whole-cell configuration using a pipette solution containing 0.025 mM EGTA, the amplitude of Ihist was initially the same as that obtained using perforated patch but then decreased; the time required for the responses to decrease to 50% (t1/2) was 8.2 +/- 1.0 min. When 1 mM EGTA was included in the pipette solution (whole-cell configuration), the initial response to histamine was significantly decreased in size and t1/2 was reduced to 3.3 +/- 0.7 min. 6. The characteristics of the signalling pathway were examined in cells studied using the whole-cell configuration with 0.025 mM EGTA in the recording pipette. Heparin significantly reduced t1/2 to 4.3 +/- 0.8 min. GTP gamma S elicited inward current and oscillations; both effects were enhanced by histamine. GTP gamma S also reduced t1/2 to 1.4 +/- 0.1 min. Pertussis toxin did not alter the amplitude or time course of Ihist. 7. We conclude that in guinea-pig tracheal myocytes, binding of histamine to H1 receptors leads to release of Ca2+ from intracellular stores and subsequent activation of Cl- and K+ conductances as well as contraction. Furthermore, we demonstrate that ACh elicits similar physiological responses due to a convergence of the histaminergic and muscarinic signalling pathways.
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PMID:Histamine activates Cl- and K+ currents in guinea-pig tracheal myocytes: convergence with muscarinic signalling pathway. 822 56

1. The actions of muscarinic agonists and antagonists upon the Ca2+ current (ICa) in acutely dissociated magnocellular cholinergic basal forebrain neurones from 11 to 14-day-old postnatal rats were studied using the whole-cell patch-clamp technique. 2. In all cells studied, muscarinic agonists inhibited a transient component of high-voltage-activated (HVA) current, but had no effect upon the low-voltage-activated (LVA) current. The mean IC50 values for ACh and oxotremorine methiodide (oxo-M), obtained from non-cumulative dose-response curves, were 204 and 363 nM respectively. Superfusion with the K+ channel blocker, tetraethylammonium chloride (TEA; 30 mM) shifted the ACh dose-response curve to the right giving an IC50 value of 22:9 microM. 3. Pirenzepine (0.1-1 microM) and methoctramine (0.03-0.3 microM) produced parallel shifts to the right in the agonist dose-response curves. Schild analysis of the agonist dose ratios yielded pA2 (negative log of the apparent dissociation constant KB) values for pirenzepine and methoctramine of 6.8 and 8.2 respectively, indicating the involvement of an M2 receptor subtype. 4. In the presence of GTP-gamma-S (10-500 microM) in the patch pipette, the agonist-induced inhibition of ICa became irreversible. Dialysis with GDP-beta-S (1 mM) abolished all agonist-induced inhibition of the Ca2+ current. The agonist-induced inhibition of ICa was totally blocked by pretreatment with pertussis toxin (500 ng ml-1) but unaffected by preincubation with cholera toxin (500 ng ml-1). Superfusion with 8-bromo cAMP (0.5-1 mM) did not mimic or prevent the effect of agonist application. 5. Inhibition of the Ca2+ current by muscarinic agonists was only partially blocked by omega-conotoxin GVIA (omega-CgTX GVIA), with approximately 46% of the agonist-sensitive current being resistant to omega-CgTX GVIA. Both the agonist- and omega-CgTX GVIA-sensitive components of the current were abolished following maximal inhibition of ICa by GTP-gamma-S. 6. These results indicate that inhibition of the Ca2+ current by muscarinic agonists is mediated via an M2 muscarinic receptor coupled to a pertussis toxin-sensitive G-protein. The possible modulation of multiple HVA Ca2+ channels by muscarinic agonists and the role that these receptors may play in presynaptic modulation of neurotransmitter release are discussed.
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PMID:M2 muscarinic receptor-mediated inhibition of the Ca2+ current in rat magnocellular cholinergic basal forebrain neurones. 841 Jun 90

1. Effects of oestradiol on the electrical and mechanical properties of the rabbit basilar artery were investigated by use of microelectrode, patch-clamp and isometric tension recording methods. 2. Oestradiol (10 nM-100 microM) relaxed arterial tissue pre-contracted by excess [K]o solution (30 mM) in a concentration-dependent manner. In Ca-free solution, histamine (10 microM) and caffeine (20 mM) each produced a phasic contraction, but oestradiol (10 microM) did not significantly affect their amplitude. 3. Oestradiol (< or = 100 microM) did not change the resting membrane potential of the artery whether in the presence or absence of TEA (10 mM). Action potentials observed in the presence of 10 mM TEA were abolished by oestradiol (100 microM). 4. Oestradiol (1 microM-100 microM) inhibited the voltage-dependent Ba current in a concentration-dependent manner. Oestradiol (100 microM) inhibited the Ba current observed in the presence of nicardipine (1 microM) more than that in the absence of nicardipine (to 31.0% vs 62.0% of control). 5. GTP gamma S (30 microM) in the pipette enhanced the inhibitory actions of oestradiol on the Ba current. On the other hand, with GDP beta S (1 mM) in the pipette, oestradiol failed to inhibit the Ba current. Pertussis toxin (PTX 3 micrograms ml-1) in the pipette totally prevented the inhibitory action of oestradiol on the Ba current. 6. Oestradiol (< or = 100 microM) had no significant effect on the outward K currents evoked by a membrane depolarization. 7. These results strongly suggest that oestradiol relaxes arterial tissue by inhibition of voltage-dependent Ca channels and that it inhibits both nicardipine-sensitive and -resistant Ca currents via a PTX-sensitive GTP-binding protein. The main target of oestradiol among the arterial Ca channels seems to be the nicardipine-resistant Ca channel, rather than the nicardipine-sensitive one.
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PMID:Oestradiol-induced relaxation of rabbit basilar artery by inhibition of voltage-dependent Ca channels through GTP-binding protein. 878 90

Acetylcholine (ACh)-induced membrane hyperpolarization was studied in freshly isolated endothelial cells from rabbit aorta. Ten microM ACh induced transient hyperpolarization due to the opening of Ca(2+)-sensitive K+ channels, sensitive to TEA and charybdotoxin (CTX). The membrane potential response was accompanied by an increase in intracellular Ca2+ [Ca2+]i. Pretreatment of endothelial cells with 20 microM ATP, 0.2 microM bradykinin or 0.1 microM platelet-aggregating factor, which induced either a transient hyperpolarization or no response, changed the subsequent ACh-induced response to a large maintained hyperpolarization. This sustained membrane hyperpolarization was also due to the opening of Ca(2+)-activated K+ channels as confirmed by CTX and TEA blockade, and was related to elevated [Ca2+]i measured by fura-2 fluorescence. Pertussis toxin blocked potentiation, indicating involvement of a G protein. The linkage to receptor-operated Ca2+ (ROC)-entry was suggested by observations that the maintained hyperpolarization during potentiation was dependent on extracellular Ca2+ and was abolished by the ROC blockers SKF-96365 and Ni2+. Inhibition of the Ca2+ pump of the endoplasmic reticulum mimicked the potentiating effect of the agonists. The results suggest that crosstalk between the agonists in endothelial cells involves Ca2+ movements and that this crosstalk is important for the generation of endothelial secretions.
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PMID:Potentiation of acetylcholine-induced responses in freshly isolated rabbit aortic endothelial cells. 886 47

1. Relaxation of the methoxamine-precontracted rat small mesenteric artery by endothelium-derived hyperpolarizing factor (EDHF) was compared with relaxation to the cannabinoid, anandamide (arachidonylethanolamide). EDHF was produced in a concentration- and endothelium-dependent fashion in the presence of NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) by either carbachol (pEC50 [negative logarithm of the EC50] = 6.19 +/- 0.01, Rmax [maximum response] = 93.2 +/- 0.4%; n = 14) or calcium ionophore A23187 (pEC50 = 6.46 +/- 0.02, Rmax = 83.6 +/- 3.6%; n = 8). Anandamide responses were independent of the presence of endothelium or L-NAME (control with endothelium: pEC50 = 6.31 +/- 0.06, Rmax = 94.7 +/- 4.6%; n = 10; with L-NAME: pEC50 = 6.33 +/- 0.04, Rmax = 93.4 +/- 6.0%; n = 4). 2. The selective cannabinoid receptor antagonist, SR 141716A (1 microM) caused rightward shifts of the concentration-response curves to both carbachol (2.5 fold) and A23187 (3.3 fold). It also antagonized anandamide relaxations in the presence or absence of endothelium giving a 2 fold shift in each case. SR 141716A (10 microM) greatly reduced the Rmax values for EDHF-mediated relaxations to carbachol (control, 93.2 +/- 0.4%; SR 141716A, 10.7 +/- 2.5%; n = 5; P < 0.001) and A23187 (control, 84.8 +/- 2.1%; SR 141716A, 3.5 +/- 2.3%; n = 6; P < 0.001) but caused a 10 fold parallel shift in the concentration-relaxation curve for anandamide without affecting Rmax. 3. Precontraction with 60 mM KCl significantly reduced (P < 0.01; n = 4 for all) relaxations to 1 microM carbachol (control 68.8 +/- 5.6% versus 17.8 +/- 7.1%), A23187 (control 71.4 +/- 6.1% versus 3.9 +/- 0.45%) and anandamide (control 71.1 +/- 7.0% versus 5.2 +/- 3.6%). Similar effects were seen in the presence of 25 mM K+. Incubation of vessels with pertussis toxin (PTX; 400 ng ml-1, 2 h) also reduced (P < 0.01; n = 4 for all) relaxations to 1 microM carbachol (control 63.5 +/- 7.5% versus 9.0 +/- 3.2%), A23187 (control 77.0 +/- 5.8% versus 16.2 +/- 7.1%) and anandamide (control 89.8 +/- 2.2% versus 17.6 +/- 8.7%). 4. Incubation of vessels with the protease inhibitor phenylmethylsulphonyl fluoride (PMSF; 200 microM) significantly potentiated (P < 0.01), to a similar extent (approximately 2 fold), relaxation to A23187 (pEC50: control, 6.45 +/- 0.04; PMSF, 6.74 +/- 0.10; n = 4) and anandamide (pEC50: control, 6.31 +/- 0.02; PMSF, 6.61 +/- 0.08; n = 8). PMSF also potentiated carbachol responses both in the presence (pEC50: control, 6.25 +/- 0.01; PMSF, 7.00 +/- 0.01; n = 4; P < 0.01) and absence (pEC50: control, 6.41 +/- 0.04; PMSF, 6.88 +/- 0.04; n = 4; P < 0.001) of L-NAME. Responses to the nitric oxide donor S-nitroso-N-acetylpenicillamine (SNAP) were also potentiated by PMSF (pEC50: control, 7.51 +/- 0.06; PMSF, 8.00 +/- 0.05, n = 4, P < 0.001). 5. EDHF-mediated relaxation to carbachol was significantly attenuated by the K+ channel blocker tetraethylammonium (TEA; 1 mM) (pEC50: control, 6.19 +/- 0.01; TEA, 5.61 +/- 0.01; n = 6; P < 0.01). In contrast, TEA (1 mM) had no effect on EDHF-mediated relaxation to A23187 (pEC50: control, 6.47 +/- 0.04; TEA, 6.41 +/- 0.02, n = 4) or on anandamide (pEC50: control, 6.28 +/- 0.06; TEA, 6.09 +/- 0.02; n = 5). TEA (10 mM) significantly (P < 0.01) reduced the Rmax for anandamide (control, 94.3 +/- 4.0%; 10 mM TEA, 60.7 +/- 4.4%; n = 5) but had no effect on the Rmax to carbachol or A23187. 6. BaCl2 (100 microM), considered to be selective for blockade of inward rectifier K+ channels, had no significant effect on relaxations to carbachol or A23187, but caused a small shift in the anandamide concentration-response curve (pEC50: control, 6.39 +/- 0.01; Ba2+, 6.20 +/- 0.01; n = 4; P < 0.01). BaCl2 (1 mM; which causes non-selective block of K+ channels) significantly (P < 0.01) attenuated relaxations to all three agents (pEC50 values: carbachol, 5.65 +/- 0.02; A23187, 5.84 +/- 0.04; anandamide, 5.95 +/- 0.02; n = 4 for each). 7. Apamin (1mu M), a selective blocker of small conductance, Ca2+-activated, K+ channels (SKCa), 4-aminopyridine (1mM), a blocker of delayed rectifier, voltage-dependent, K+ channels (Kv), and ciclazindol (10mu M), an inhibitor of Kv and adenosine 5'-triphosphate (ATP)-sensitive K+ channels (KATP), significantly reduced EDHF-mediated relaxations to carbachol, but had no significant effects on A23187 or anandamide responses. 8. Glibenclamide (10mu M), a KATP inhibitor and charybdotoxin (100 or 300nM), a blocker of several K+ channel subtypes, had no significant effect on relaxations to any of the agents. Iberiotoxin (50nM), an inhibitor of large conductance, Ca2+-activated, K+ channels (BKCa), had no significant effect on the relaxation responses, either alone or in combination with apamin (1muM). Also, a combination of apamin (1muM) with either glibenclamide (10muM) or 4-aminopyridine (1mM) did not inhibit relaxation to carbachol significantly more than apamin alone. Neither combination had any significant effect on relaxation to A23187 or anandamide. 9. A combination of apamin (1muM) with charybdotoxin (100nM) abolished EDHF-mediated relaxation to carbachol, but had no significant effect on that to A23187. Apamin (1muM) and charybdotoxin (300nM) together consistently inhibited the response to A23187, while apamin (1muM) and ciclazindol (10muM) together inhibited relaxations to both carbachol and A23187. None of these toxin combinations had any significant effect on relaxation to anandamide. 10. It was concluded that the differential sensitivity to K+ channel blockers of EDHF-mediated responses to carbachol and A23187 might be due to actions on endothelial generation of EDHF, as well as its actions on the vascular smooth muscle, and suggests care must be taken in choosing the means of generating EDHF when making comparative studies. Also, the relaxations to EDHF and anandamide may involve activation of cannabinoid receptors, coupled via PTX-sensitive G-proteins to activation of K+ conductances. The results support the hypothesis that EDHF is an endocannabinoid but relaxations to EDHF and anandamide show differential sensitivity to K+ channel blockers, therefore it is likely that anandamide is not identical to EDHF in the small rat mesenteric artery.
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PMID:A comparison of EDHF-mediated and anandamide-induced relaxations in the rat isolated mesenteric artery. 942 1

Peptides release histamine from enterochromaffin-like (ECL) cells because of elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) by either receptor-operated or voltage-dependent Ca(2+) channels (VDCC). To determine whether VDCCs contribute to histamine release stimulated by gastrin or pituitary adenylate cyclase-activating polypeptide (PACAP), the presence of VDCCs and their possible modulation by peptides was investigated in a 48-h cultured rat gastric cell population containing 85% ECL cells. Video imaging of fura 2-loaded cells was used to measure [Ca(2+)](i), and histamine was assayed by RIA. Cells were depolarized by increasing extracellular K(+) concentrations or by 20 mM tetraethylammonium (TEA(+)). Cell depolarization increased transient and steady-state [Ca(2+)](i) and resulted in histamine release, dependent on extracellular Ca(2+). These K(+)- or TEA(+)-dependent effects on histamine release from ECL cells were coupled to activation of parietal cells in intact rabbit gastric glands, and L-type channel blockade by 2 microM nifedipine inhibited 50% of [Ca(2+)](i) elevation and histamine release. N-type channel blockade by 1 microM omega-conotoxin GVIA inhibited 25% of [Ca(2+)](i) elevation and 14% of histamine release. Inhibition was additive. The effects of 20 mM TEA(+) were fully inhibited by 2 microM nifedipine. Both classes of Ca(2+) channels were found in ECL cells, but not in parietal cells, by RT-PCR. Nifedipine reduced PACAP-induced (but not gastrin-stimulated) Ca(2+) entry and histamine release by 40%. Somatostatin, peptide YY (PYY), and galanin dose dependently inhibited L-type Ca(2+) channels via a pertussis toxin-sensitive pathway. L-type VDCCs play a role in PACAP but not gastrin stimulation of histamine release from ECL cells, and the channel opening is inhibited by somatostatin, PYY, and galanin by interaction with a G(i) or G(o) protein.
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PMID:Role of neuropeptide-sensitive L-type Ca(2+) channels in histamine release in gastric enterochromaffin-like cells. 1060 Aug 25


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