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  • Depolarization  (3)
  • Permeability  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Changes in erythrocyte permeability due to palytoxin as compared to amphotericin B
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 688 (1982), S. 486-494 
    Details
    ISSN: 0005-2736
    Keywords: (Erythrocyte) ; Amphotericin B ; Palytoxin ; Permeability
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0005-2736(82)90360-1
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  • 2
    Electronic Resource
    Electronic Resource
    Ouabain inhibits the increase due to palytoxin of cation permeability of erythrocytes (1982)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 319 (1982), S. 101-107 
    Details
    ISSN: 1432-1912
    Keywords: Palytoxin ; Ouabain ; Erythrocytes ; Permeability ; ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Palytoxin in concentrations as low as 1 pM raises the potassium permeability of rat, human and sheep erythrocytes, and the sodium permeability of human erythrocytes. The release of potassium or sodium from human cells also occurs when extracellular sodium is replaced by choline. 2. Ouabain inhibits the release due to palytoxin of potassium ions from human, sheep and rat erythrocytes, and also the release of sodium ions from human cells. The glycoside effect is specific since a) it is already prominent with 5×10−8 M ouabain b) rat erythrocytes are less sensitive than human cells to ouabain c) potassium release due to amphotericin B or the Ca2+ ionophore A23187 is not influenced by ouabain and d) dog erythrocytes are resistant to palytoxin as well as to ouabain. 3. Palytoxin has no direct influence on the Na+, K+-ATPase. It inhibits the binding of [3H]ouabain to erythrocyte membranes within the same concentration range as unlabelled ouabain. It partially displaces bound [3H]ouabain, and partially inhibits the inactivation of erythrocyte ATPase by the glycoside. Depletion of ATP or of external Ca2+ renders the cells less sensitive to palytoxin. Nevertheless inhibition by ouabain can be still demonstrated with human cells whose ATP stores had been largely exhausted, and also in the absence of external Ca2+. 4. Palytoxin decreases the surface tension at the air-water interface. We assume that the formation of nonspecific pores by palytoxin is linked with its surface activity. Further experiments should demonstrate whether ouabain prevents the binding of palytoxin to erythrocytes (“receptor hypothesis”), or whether an ouabain-sensitive hydrolysis of trace amounts of ATP (“metabolic hypothesis”) promotes the palytoxin effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00503920
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  • 3
    Electronic Resource
    Electronic Resource
    Action and binding of palytoxin, as studied with brain membranes (1983)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 323 (1983), S. 269-275 
    Details
    ISSN: 1432-1912
    Keywords: Palytoxin ; Tetraphenylphosphonium ; Depolarization ; Binding ; Borate ; Calcium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Palytoxin in concentrations as low as 10−11 to 10−12 M promotes the outflow of the lipophilic [3H]-tetraphenylphosphonium ion from particulate brain cortex of guinea-pigs and rats, and from preloaded crude synaptosomes of rats, which indicates depolarization. The outflow is not influenced by tetrodotoxin or the calcium channel blocker nimodipin, or by substitution of choline for Na+ ions. It is increased by Ca2+ and by borate, the latter interacting with the toxin itself. To assess the fixation of palytoxin to biological membranes, a binding step was installed before the depolarization step. Palytoxin binds to membranes from rat brain, liver, kidney, human and dog erythrocytes, and to a lesser degree to liposomes made from rat brain or erythrocyte lipids. Binding is reversible. It is decreased by mild physical pretreatments of crude synaptosomes. Palytoxin binding is increased in the presence of micromolar concentrations of Ca2+ or borate. It is concluded that the potentiation of palytoxin actions by Ca2+ or borate is at least partially due to the promotion of its binding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00497673
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  • 4
    Electronic Resource
    Electronic Resource
    Zur Frage der Bedeutung des Kininsystems beim thermischen Ödem der Rattenpfote (1969)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 264 (1969), S. 476-493 
    Details
    ISSN: 1432-1912
    Keywords: Kinins ; Permeability ; Heat ; Inflammation ; Kinine ; Permeabilität ; Hitze ; Entzündung
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The suboutis of rat paws heated (46,5° C) in situ has been perfused. Kinin activity could be demonstrated regularly in the fluid which was collected in ice. When the solutions were tested immediately after having passed the tissue, only some of the experiments yielded positive results. Native and125Jlabelled kininogen as well as kininogenase and kininase activities passed into the perfusates. The sensitivity to dextran and the kinin release on heating were, in contrast to recent reports, not correlated. 2. The release of the components of the kinin system approximately paralleled that of labelled human albumin. Their concentration rose until about 1 hour after the start of the heating. There was no priority of the components of the kinin system when compared with human albumin which can be regarded as permeability indicator. 3. Intravenously injected carboxypeptidase B, because of its lower molecular weight, entered the interstitial fluid more easily than did the plasma carboxypeptidase N. Its blood level decreased rapidly; but sufficient tissue concentrations could be maintained by intravenous infusions. Neither the volume nor the time dependence of the thermic edema changed during carboxypeptidase B-infusions. The same was true for infusions of trasylol, whereas phenylbutazone inhibited the edema significantly. Edema formed by short heating (30 sec, 55° C) was equally resistant to carboxypeptidase B. 4. In the skin and muscles of the heated rat paw, carbon particles mainly stained the capillary walls. This finding argues against a considerable involvement of “classical” mediators which should induce venular lesions. 5. Infusion of large amounts of bradykinin into the arterial supply did not imitate the thermic edema; neither has bradykinin been found in the perfusate of the subcutis. 6. In the light of these findings, a significant role of the kinin system in the thermic edema of the rat paw is to be doubted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01002384
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  • 5
    Electronic Resource
    Electronic Resource
    Depolarization increases inositolphosphate production in a particulate preparation from rat brain (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 334 (1986), S. 1-9 
    Details
    ISSN: 1432-1912
    Keywords: Depolarization ; Ion channels ; Phosphatidylinositol ; Inositol phosphates ; Voltage-dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the accumulation of inositol phosphates (InsP) due to depolarization. A particulate preparation of rat brain was introduced to rule out transmitter activated mechanisms and to allow free access for drugs of high molecular weights. Potassium depolarization doubled InsP within a few minutes. InsP accumulation depended on time and K+ concentration, and was affected neither by tetrodotoxin nor by atropine. Radioactive metabolites co-eluted with inositol mono-phosphate and inositol bis-phosphate, whereas only minor amounts appeared with inositol tris-phosphate. The content in phosphatidylinositols was decreased. No evidence was found for the involvement of a neurotransmitter. Sea anemone toxin II (around 1 μmol/l), which keeps the Na+-channels open, promoted the InsP accumulation in an atropine-resistant manner. Tetrodotoxin prevented it when given before, and inhibited it when given after initiation by sea anemone toxin II. Moreover the K+ channel blockers 4-aminopyridine, dendrotoxin and tetraethylammonium all caused InsP accumulation. Palytoxin was by far the most potent promoter of InsP accumulation with a detection limit below 10 pmol/l, and displayed a unique bell-shaped concentration-effect correlation. Ouabain (3 μmol/l) and above) also elicited the InsP accumulation. The response to carbachol was not only inhibited completely by atropine, but also partially (more than 50%) by tetrodotoxin, which indicates the involvement of voltage-dependent sodium channels in the receptor-triggered InsP accumulation. Thus independent of the causative agent, depolarization promotes an InsP accumulation. We conclude that degradation of phosphatidylinositols is mediated not only by receptor occupation but also by a positive shift in membrane voltage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00498733
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  • 6
    Electronic Resource
    Electronic Resource
    Electrophysiological and neurobiochemical evidence for the blockade of a potassium channel by dendrotoxin (1985)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 330 (1985), S. 77-83 
    Details
    ISSN: 1432-1912
    Keywords: Dendrotoxin ; Potassium channel ; Nerve fibre ; Depolarization ; GABA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of dendrotoxin (DTX), a toxic peptide from Dendroaspis angusticeps venom, were studied electrophysiologically on peripheral frog nerve fibres, and biochemically on large synaptosomes from rat brain. 1. On nerve fibres, DTX reduced the amplitude and prolonged the duration of the action potential; even at 0.1 nmol/l DTX produced significant effects. Maximum block of potassium currents occurred at about 30 nmol/l. Turning on of the remaining current was slowed. Reversibility was incomplete. The reduction of potassium currents was between 31% and 85% at 85 nmol/l DTX (n=8). The remainder appeared to be resistant to DTX. Sodium channels were not affected. 2. On large synaptosomes DTX (above 1 nmol/l) produced a slight depolarization, indicated by an outward shift of the lipophilic cation tetraphenylphosphonium, and promoted the release of radioactivity after preloading with [3H] GABA. DTX had similar potency but lower efficacy in this respect than sea anemone toxin II (ATX II). In contrast to the effects of ATX II, those due to DTX were only partially inhibited by tetrodotoxin. The actions of 4-aminopyridine resembled those of DTX, but the latter was about 500 times more potent. The electrophysiological data provide direct evidence for blockade of a potassium channel by DTX. This action is sufficient to explain the biochemical observations, although additional effects on synaptosomes cannot be excluded.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00499898
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