Specific Uncoupling of Excitation and Contraction in Mammalian Cardiac Tissue by Lanthanum

Sanborn, W. G.; Langer, G. A.

doi:10.1085/jgp.56.2.191

Cited by 129 publications

(48 citation statements)

References 30 publications

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“…The increased duration of the Purkinje cell action potential found by us confirms similar findings reported by Sanborn and Langer (20) in rabbit ventricular cardiac cells . These authors reported the displacement by lanthanum of calcium bound superficially, probably to the sarcolemma (20) . In view of these results, the possibility exists that the regions where selective deposition of lanthanum was observed in the present study could represent the sites where contractile dependent calcium is normally bound .…”

Section: Ultrastructural Localization Of Lanthanum Depositsmentioning

confidence: 97%

Selective Deposition of Lanthanum in Mammalian Cardiac Cell Membranes

Martı́nez-Palomo

Benítez

Alanís

1973

The Journal of Cell Biology

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Perfusion of beating false tendons of the dog heart with ionic lanthanum produced drastic but reversible modifications of the excitability and the transmembrane action potential of Purkinje cells . Ultrastructural examination of these cells revealed the appearance of a fine extracellular precipitate detectable on unstained sections . In addition, specimens perfused with La+++ showed a striking increase in the contrast of the sarcolemma, particularly in gap junctions and in pinocytic vesicles . La+++ deposits were restricted to the cytoplasmic leaflets of the sarcolemma ; no precipitates were found at the plasma membrane of fibroblasts, endothelial and smooth muscle cells, or unmyelinated nerve fibers present in the same specimens . A selective deposition of La+++ was also observed in the sarcolemma of atrial and ventricular cells of dog, rabbit, and cat hearts, as well as in the membrane of the transverse tubular system of ventricular cells . Both the electrophysiological effects and the ultrastructural membrane deposits produced by La+++ disappeared when the specimens were subsequently perfused with phosphate-containing tyrode solution . These results tend to demonstrate that a distinctive feature of the sarcolemma of mammalian cardiac cells is the presence of regions with a high surface density of binding sites for polyvalent cations.

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Section: Ultrastructural Localization Of Lanthanum Depositsmentioning

confidence: 97%

Selective Deposition of Lanthanum in Mammalian Cardiac Cell Membranes

Martı́nez-Palomo

Benítez

Alanís

1973

The Journal of Cell Biology

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“…It is generally supposed that a primary and essential step for the influx of Ca2+ is the binding to surface membranes in barnacle muscle (HAGIWARA and TAKA-HASHI, 1967), mammalian myocardial tissues (SANBORN and LANGER, 1970) and isolated skeletal sarcoplasmic reticulum (CHEVALLIER and BUTOW,1971 tonic component was more marked than that of phasic one.…”

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confidence: 99%

Selective Inhibition of Potassium Contracture in Guinea Pig Taenia Coli by Ruthenium Red

Kawamura¹,

Yabu²

1978

Jpn.J.Physiol

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Effects of ruthenium red on isotonic KCl induced contracture (K-contracture), cellular 45Ca uptake and 45Ca binding to surface membranes were examined in the smooth muscle cells of guinea pig taenia coli. These results were compared with those using lanthanum (La3+). The tonic component of the K-contracture was selectively inhibited by 1 mM ruthenium red. In contrast, 1 mivt La3+ inhibited the phasic component of the K-contracture to a large extent. Use of 1 mM ruthenium red selectively inhibited the tonic component of K-contracture and caused a marked decrease in cellular 45Ca uptake in that component of K-contracture. In contrast, 1 mM La3+ largely inhibited the phasic component and caused a significant decrease in cellular 45Ca in that component. According to Scatchard plot analysis, there are two kinds of Ca2+ binding sites of high and low affinity, respectively, on the surface membrane of the taenia coli. One mM ruthenium red suppressed those of low affinity more strongly than those of high affinity. In contrast, 1 mM La3+ suppressed high affinity sites more markedly than low affinity sites. Based on these results, it seems possible to conclude that ruthenium red mainly blocks the initial binding sites linked with Ca2+ influx which is related to the production of the tonic component while La3+ blocks those sites related to the phasic component of the K-contracture of guinea pig taenia coli.

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“…On the other hand, La3+ equally suppressed the actions of HL-A, isoprenaline and ouabain. This is reasonable because La3' decreases any Ca movement across the membrane (Sanborn & Langer, 1970;Langer & Frank, 1972;Reeves & Sutko, 1979;Burt & Langer, 1982). Second, both HL-A and isoprenaline augmented the contraction of partially depolarized muscles depending on the external Ca concentration while ouabain failed to do so.…”

Section: Discussionmentioning

confidence: 91%

Positive inotropic action of saponins on isolated atrial and papillary muscles from the guinea‐pig

Enomoto

Ito

Kawagoe

et al. 1986

British J Pharmacology

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The effects of several saponins of animal and plant origin on the contractile activity of atrial and papillary muscles of the guinea‐pig were tested. In a concentration of 1 × 10−5 M, holothurin‐A (HL‐A), holothurin‐B, echinoside‐A, echinoside‐B and sakuraso‐saponin (Saku) exhibited positive inotropic and chronotropic actions whereas desacyl‐jego‐saponin and ginsenoside‐Rd did not. Saponins having a positive inotropic action caused haemolysis of rabbit erythrocytes whereas those without inotropic action did not cause haemolysis. The positive inotropic action of saponins was not affected by practolol, chlorpheniramine, cimetidine and indomethacin. Verapamil (10−6 M) inhibited the inotropic actions due to HL‐A and isoprenaline (10−8 M) to the same extent but had a small efect on those due to ouabain (10−7 M). In high K+ (30 mM K+) medium where the action potential and the contraction were depressed, HL‐A, Saku and isoprenaline restored the action potential and the contraction of the ‘slow response’ type whereas ouabain failed to do so. In normal medium HL‐A and Saku reduced the resting membrane potential by 15–20 mV. These results suggest that modification of the Ca channel is involved in the positive inotropic action of saponins.

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Specific Uncoupling of Excitation and Contraction in Mammalian Cardiac Tissue by Lanthanum

Cited by 129 publications

References 30 publications

Selective Deposition of Lanthanum in Mammalian Cardiac Cell Membranes

Selective Deposition of Lanthanum in Mammalian Cardiac Cell Membranes

Selective Inhibition of Potassium Contracture in Guinea Pig Taenia Coli by Ruthenium Red

Positive inotropic action of saponins on isolated atrial and papillary muscles from the guinea‐pig

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