Effect of Manganese Ions on Excitationcontraction Coupling in Frog Sartorius Muscle

Oota, Isao; Takauji, Masa; Nagai, Torao

doi:10.2170/jjphysiol.22.379

Cited by 32 publications

(24 citation statements)

References 20 publications

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“…This was also a transient effect; pre-manganese levels were attained within 10-15 min. A similar inhibitory effect of manganese ions on contractile responses has been reported for the skeletal muscles of the frog (OOTA et al, 1972;CHIARANDINI and STEFANI, (1973) and for the isolated frog atrial trabeculae (CHAPMAN and OCHI, 1971).…”

Section: Propagation In Innervated Fibressupporting

confidence: 76%

Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

López

1979

Jpn.J.Physiol

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Denervated frog's semitendinosus muscles were studied. Fibrillation potentials generate propagated spikes which are conducted at a rate similar to that calculated for innervated muscles. The twitch tension per unit area was similar in denervated and innervated single fibres; the average value corresponded with values reported in the literature for fibres stimulated at 125/sec. Manganese ions (1-3 mM), selectively inhibit fibrillation potentials and have no appreciable effect upon evoked spikes. Mn2+ also inhibits (40-50%) the twitch responses and abolishes the resting tension of muscle fibres. The latter effects were observed in denervated as well as in innervated preparations when the fibres studied belonged to fascicles located at the site of entrance of the nerve. Disruption of the transverse tubular system by glycerol treatment does not interfere with the generation of fibrillation potentials, although the effects on twitching are similar to those reported in the literature. A possible mechanism is proposed to explain the generation of fibrillation potentials in frog denervated muscles.The fibrillatory activity of the denervated semitendinosus muscle of the frog has been described in a previous paper (LOPEZ, 1978). It was mentioned, as a possibility to explain the poor tension development occasionally observed in that study, that fibrillation potentials might not give rise to propagated electrical activity. It was also considered that the transverse tubular system (TTS), a possible site of origin of the discrete depolarizations found in denervated mammalian muscles (PURVES and SAKMANN, 1974;SMITH and THESLEFF, 1976), could provide an explanation to the fact that, in the frog, it is possible to obtain spontaneous depolarizations, and repetitive firing, from any spot along the muscle length.On these bases, the present study was aimed at obtaining further information related to the propagation of fibrillation potentials and inquiring further about the role the TTS may possibly play in the genesis of the electrical fibrillatory activity. The results obtained during the study are described in this paper.

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Section: Propagation In Innervated Fibressupporting

confidence: 76%

Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

López

1979

Jpn.J.Physiol

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“…7A) (Miller & Moiscescu, 1976). If R has a separate activator site like that suggested by Baker et al (1969) (Oota et al 1972;Chiarandini & Stefani, 1973), where it seems likely that these effects are due largely to the neutralization of membrane surface negative charges. 350 Mn AND CONTRACTION As discussed above, extracellular Mn does have effects on the action potential and its threshold, in frog heart, that could be due to the neutralization of negative charges on the surface of the cell membrane.…”

Section: Discussionmentioning

confidence: 92%

The effects of manganese ions on the contraction of the frog's heart

Chapman¹,

Ellis²

1977

The Journal of Physiology

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SUMMARY1. The effects of Mn2+ in particular but also of Ni2+, C02+, Cd2+, verapamil and D600 on the contraction of isolated frog atrial trabeculae have been investigated. Contraction was initiated either by electrical stimulation, or by raising the [K] 3. Mn ions reduce the strength of the regularly evoked heart beats.Prolonged exposure, in beating hearts, results in a rise in resting tension and often a small recovery of the heart beat.4. In normal Ringer solution and in Ringer free of Na ions, the addition of Mn causes the tension-depolarization curve to be displaced by an amount equivalent to an 18 mV hyperpolarization of the membrane potential for a tenfold increase in the divalent cation concentration.5. MIn, Co, Ni and Cd ions all cause a marked reduction in the tension generated by exclusion of Na ions from the bathing fluid. In the presence of these divalent cations the contracture divides into an initial phasic and a later tonic contraction. This inhibition is reversed by raising the [Ca] 6. A similar tonic contracture is initiated after exposure to Na-free fluid containing a high [Mn]o by the addition of a small concentration of Na, Li, hydrazinium or hydroxylammonium ions.7. The organic 'Ca antagonists' verapamil and D600 have little effect on the contracture induced by lowering [Na]o even after prolonged exposure at relatively high concentrations but they do inhibit the twitch contraction and the K contractures.

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“…Post-rest contraction and rapid cooling contracture have been used as an index of SR function. 5 11) but this has to be confirmed in cardiac muscle. Mn 2ϩ was reported to enter the mitochondria and affect Ca 2ϩ efflux into the cytoplasm.…”

Section: Discussionmentioning

confidence: 99%

Effect of Manganese on Guinea Pig Ventricle: Initial Depression and Late Augmentation of Contractile Force.

Tanaka

Ishii

Fujisaki

et al. 2002

Biological & Pharmaceutical Bulletin

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Mn2ϩ is widely used as an inorganic Ca 2ϩ channel blocker to assess the role of slow inward current in myocardial excitation-contraction coupling. In addition to its well documented negative inotropic effects, Mn 2ϩ is also reported to have positive inotropic effects. 1) Enhancement of sarcoplasmic reticulum (SR) function2) and inhibition of Ca 2ϩ extrusion 1) have been proposed to underlie this positive effect. Also in smooth muscles, enhancement of contraction by Mn 2ϩ has been reported, and some investigators propose an intracellular site of action.3) In the present study, we applied Mn 2ϩ to guinea pig papillary muscles to obtain information on its positive inotropic effect. MATERIALS AND METHODSHearts were rapidly isolated from guinea pigs of either sex (250-300 g) and right ventricular papillary muscles were dissected out and placed horizontally in a 20 ml organ bath containing physiological salt solution of the following composition (mM concentration): NaCl 135, KCl 5, CaCl 2 2, MgCl 2 1, NaHCO 3 15 and glucose 5.5 (pH 7.4). The nutrient solution was aerated with 95% O 2 -5% CO 2 and maintained at 36.5°C. The preparations were driven by a pair of platinum plate electrodes (field stimulation) with rectangular current pulses (1 Hz, 5 ms 1.2ϫ threshold voltage) generated by an electronic stimulator (Dia Medical System, DPS-165B). The resting tension applied to each preparation was adjusted so that the muscle was stretched to the peak of its length-tension curve. Developed tension was recorded isometrically with a force-displacement transducer (Nihon Kohden TB-611T) connected to a minipolygraph (Nihon Kohden RM-6100). Mn 2ϩ and drugs were added after preparations were allowed to equilibrate for more than 40 min, after which the developed tension of the preparations was well maintained. All drug solutions were prepared immediately before the start of the experiments by dissolving them in distilled water. A small aliquot of the solution was added to the bath to give the desired final concentration. The contractile force after each addition was expressed as a percentage of the force in the absence of drugs. For rapid-cooling-contracture measurements, the preparations were placed in a stream of physiological salt solution and contractile force was measured as above. Twenty seconds after the termination of normal electrical field stimulation at 1 Hz, contracture was induced by rapidly dropping the temperature of the solution from 36.5 to 1°C. Ventricular myocytes were prepared from adult guinea pigs of both sexes by Langendorf perfusion and collagenase digestion as previously described. 4) Cells were then plated on coverslips attached to an experimental chamber and preincubated for 30 min with 10 mM fura-2-AM, after which the chamber was placed on a fluorescence microscope (Olympus IX70), and the cells were washed by perfusion with the physiological salt solution mentioned above. Cells were excited at 360 nm and fluorescence images were obtained with a cooled CCD camera (C-6970; Hamamatsu Photonics). The fluoresce...

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Effect of Manganese Ions on Excitationcontraction Coupling in Frog Sartorius Muscle

Cited by 32 publications

References 20 publications

Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

Denervated Muscle: Rate of Propagation and Effects of Manganese Ions and Glycerol on the Fibrillatory Activity of Frog Semitendinosus

The effects of manganese ions on the contraction of the frog's heart

Effect of Manganese on Guinea Pig Ventricle: Initial Depression and Late Augmentation of Contractile Force.

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