Selective inhibition of the transmembrane Ca conductivity of mammalian myocardial fibres by Ni, Co and Mn ions

Kohlhardt, M.; Bauer, Benedikt; Krause, H.; Fleckenstein, A.

doi:10.1007/bf00592747

Cited by 156 publications

(32 citation statements)

References 10 publications

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“…Augmenting (Baker, Meves & Ridgway, 1973) and mammalian heart muscle (Kohlhardt, Bauer, Krause & Fleckenstein, 1973). In order further to test the possibility that a small part of the ACh-induced depolarizing current is carried by Ca, some experiments with solutions containing Mn (2 mm) or D-600 (0-1 mm) were carried out.…”

Section: Part I Experiments In Which Ach Was Added Directlymentioning

confidence: 99%

Pancreatic acinar cells: ionic dependence of acetylcholine‐induced membrane potential and resistance change.

Nishiyama¹,

Petersen²

1975

The Journal of Physiology

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SUMMARY1. Intracellular recordings of membrane potential, input resistance and time constant have been made in vitro from the exocrine acinar cells of the mouse pancreas using glass micro-electrodes. The acinar cells were stimulated by acetylcholine (ACh). In some cases ACh was simply directly added to the tissue superfusion bath, in other experiments ACh was applied locally to pancreatic acini by micro-iontophoresis.2. Current-voltage relations were investigated by injecting rectangular de-or hyperpolarizing current pulses through the recording microelectrode. Within a relatively wide range (-20 to -70 9. These results indicate that ACh acts on the acinar cells by increasing the conductance of the plasma membrane to Na and K mainly but possibly 432 ACINAR CELL ELECTROPHYSIOLOGY also to other ions. There is, however, no evidence for an ACh-induced change in membrane Ca conductance. Extracellular Ca appears to control the PNa/PK ratio.

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Section: Part I Experiments In Which Ach Was Added Directlymentioning

confidence: 99%

Pancreatic acinar cells: ionic dependence of acetylcholine‐induced membrane potential and resistance change.

Nishiyama¹,

Petersen²

1975

The Journal of Physiology

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“…Recent investigations have demonstrated that Co inhibits passive Ca2+ influx associated with the action potentials in the barnacle giant muscle fibre (Hagiwara & Takahashi, 1967) and in neurones of the Aplysia visceral ganglion (Geguldig & Junge, 1968) and the slow Ca++ inward current of mammalian cardiac muscle fibres (Kohlhardt, Bauer, Krause & Fleckenstein, 1973). If this is also the case in motor nerve terminals, one may expect that the application of Co2+ may interfere with the quantal release of transmitter at the neuromuscular junction in response to a motor nerve impulse.…”

Section: Introductionmentioning

confidence: 99%

The action of cobalt ions on neuromuscular transmission in the frog

Weakly¹

1973

The Journal of Physiology

208

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SUMMARY1. Cobalt ions, in concentrations of 0-05-2 mm, block neuromuscular transmission in the frog sartorius muscle.2. The reduction in the e.p.p. amplitude produced by Co2+ is due to a decrease in the amount of transmitter released by a nerve impulse (mean quantum content). This reduction is associated with little change in the resting membrane potential of the muscle fibre or in the mean amplitude of spontaneous m.e.p.p.s.3. The reduction in evoked transmitter release produced by Co2+ may be antagonized by elevation of the external Ca2+ concentration. It is suggested that the antagonism between Co2+ and Ca2+ is competitive in nature.4. The mean dissociation constant for Co2+ and its hypothetical membrane complex was found to be 0418 mm. On this basis, it is concluded that Co2+ is about 20 times more potent than Mg2+ in suppressing evoked transmitter release.5. In contrast to the inhibitory action on evoked release, Co2+ increases spontaneous transmitter release. However, concentrations of Co2+ 20-60 times greater than those which decrease the e.p.p. amplitude are needed to produce a significant increase in m.e.p.p. frequency.

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“…The mechanism of increased F,,,a,, by Mn is obscure from the present experiments, however, the paradoxical positive isotropic effect of Mn on isolated guinea-pig myocardium has been reported (5). It has also been reported that Mn blocked Ca influx in various excitable cells (6,7,8). Moreover, the evidence that Mn carried transmembrane inward current suggests that Mn directly affects the contractile protein complex (9,10,11).…”

mentioning

confidence: 84%

Differences in Speed and Degree of Myosin B Superprecipitation in the Presence of Divalent Cations

Yajima

Takeya

1979

Japanese Journal of Pharmacology

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Efforts have been made to acquire precise quantitative evaluation for the superpre cipitation of contractile protein myosin B. Ebashi first reported a method for evaluating the degree of superprecipitation by turbidinietry at 660 m,,i (1). Watanabe used two parameters for study of superprecipitation; the time required to reach the half maximum increase in tur bidity (to .,) and the maximum increase in turbidity* (JOD, extent) (2). In the present experiments, we introduced the velocity of superprecipitation at t0.5 (Vt0.5) in addition to the above two parameters (Fig. 1). The objective was to obtain information concerning the effects of Ca, Mg and Mn on these three parameters.Myosin B was extracted from the leg muscle of rabbit (1). The superprecipitation of myosin B was continuously measured using a spectrophotometer at 660 mgt (Hitachi 100-01) and the findings were displayed on paper (National pen recorder VP-654B). The reaction mixture in a total volume of 3.0 ml, contained 0.6 mg/ml myosin B, 0.06 M Tris-maleate T We termed this parameter F,,, ,,5.

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Selective inhibition of the transmembrane Ca conductivity of mammalian myocardial fibres by Ni, Co and Mn ions

Cited by 156 publications

References 10 publications

Pancreatic acinar cells: ionic dependence of acetylcholine‐induced membrane potential and resistance change.

Pancreatic acinar cells: ionic dependence of acetylcholine‐induced membrane potential and resistance change.

The action of cobalt ions on neuromuscular transmission in the frog

Differences in Speed and Degree of Myosin B Superprecipitation in the Presence of Divalent Cations

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