The effect of substances releasing intracellular calcium ions on sodium‐dependent calcium efflux from guinea‐pig auricles.

Jundt, H; Porzig, H.; Réuter, H.; Stucki, Jörg W.

doi:10.1113/jphysiol.1975.sp010888

Cited by 160 publications

(64 citation statements)

References 39 publications

(54 reference statements)

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“…This result is consistent with the finding of Busselen and Van Kerhove (1978) that caffeine increased the efflux of "'Ca from goldfish ventricle in the absence of Na.. However, Jundt et al (1975) noted that in guinea pig atria, caffeine in the absence of extracellular Na produced a contracture, without increasing "Ca efflux . Thus, the relative importance of the Na,,-independent Ca extrusion system in cardiac tissue may vary from preparation to preparation .…”

Section: Discussionsupporting

confidence: 82%

External Na-independent Ca extrusion in cultured ventricular cells. Magnitude and functional significance.

Barry

Rasmussen

Ishida

et al. 1986

The Journal of General Physiology

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The relative magnitudes and functional significance of Ca extrusion by Na-Ca exchange and by an Na.-independent mechanism were investigated in monolayer cultures of chick embryo ventricular cells. Abrupt exposure of cells in 0-Na., nominally 0-Ca. solution to 20 mM caffeine produced a large contracture (3 .94 ± 0.90 um of cell shortening) that relaxed with a tl, of 8.60 ± 1 .22 s. An abrupt exposure to caffeine plus 140 mM Na resulted in a contracture that was smaller in amplitude (1 .53 ± 0.50,um) and relaxed much more rapidly (t,, = 0.77 ± 0 .09 s) . An abrupt exposure to caffeine in 0-Na. solutions produced an increase in "Ca efflux that persisted for 20 s, and a net loss of Ca content, determined by atomic absorption spectroscopy (AAS), of^-4 nmol/mg protein, within 35 s. A comparable net loss of Ca was demonstrated in the presence of 100 jM [Ca]o. The abrupt exposure of cultured cells to 0 Na. in 1 .8 mM Ca produced a Ca uptake, estimated with 45 Ca, of 3.2 nmol/mg protein -15 s, but produced no increase in cell Ca content (AAS). In cells in which a 30% increase in Nai was produced by 5 min exposure to 10 -6 M ouabain, the abrupt exposure to 0 Na. produced a Ca uptake of 6 nmol/mg protein -15 s and an increase in Ca content (AAS) of 4 nmol/mg protein. We conclude that there is an Na.-independent mechanism for Ca extrusion in these cells, presumably a Ca-ATPase Ca pump, with a limited Ca transport capacity of no more than 2 nmol/mg protein -15 s. This is five times smaller than the demonstrated maximum capacity of the Na-Ca exchanger in these cells. The relaxation of twitch tension in these cells seems to be dependent primarily on sarcoplasmic reticulum uptake of Ca, with a secondary role provided by the Na-Ca exchanger. The Ca pump appears to contribute little to beat-to-beat relaxation .

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Section: Discussionsupporting

confidence: 82%

External Na-independent Ca extrusion in cultured ventricular cells. Magnitude and functional significance.

Barry

Rasmussen

Ishida

et al. 1986

The Journal of General Physiology

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“…The late sustained tension seems to be caused by the inflow of Ca from the extracellular sites, because it lasted as long as the muscle was exposed to Ca-rich solution containing caffeine and was dependent on external Ca concentration. JUNDT et al (1975) showed that the Ca turnover rate across the membrane was increased by caffeine in the presence of Na. We have, however, no direct evidence concerning the origin of late tension.…”

mentioning

confidence: 99%

Caffeine Contracture in Frog Cardiac Muscle after Exposure to High Concentrations of Calcium

Matsumura

Narita

1980

Jpn.J.Physiol

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“…This value is not universally accepted (Jundt, Portzig, Reuter & Stucki, 1975), although their appears to be agreement that in squid axons Na-Ca exchange is electrogenic (Blaustein, 1976;Baker & McNaughton, 1976). These experiments do not exclude, for instance, the possibility that the carrier is voltage dependent.…”

Section: Removal Of Acsmentioning

confidence: 99%

Sodium efflux in rabbit myocardium: relationship to sodium—calcium exchange

Bridge

Cabeen

Langer

et al. 1981

The Journal of Physiology

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SUMMARY1. The washout of 22Na, 45Ca and 58CoEDTA-has been observed in arterially perfused rabbit interventricular septa both in the presence and absence ofintoxicating doses of the aglycone, 3 acetylstrophanthidin (ACS).2. The washout of 22Na from paced septa (21P0/min) was rapid with approximately 99 % of the exchange occurring in 30 min.3. Septa labelled with 22Na and washed out in the presence of 10-5 M-ACS were quiescent, exhibited marked contracture and a slowed 22Na exchange with 99 % of the initial 22Na leaving the tissue in approximately 200 min.4. Comparison of the washout of the extracellular marker 58CoEDTA-from paced and intoxicated septa revealed no differences, suggesting that regions of the extracellular space had not become inexchangeable as a result of the contracture that these septa exhibited.5. Simultaneous measurements of the distribution of 22Na and 58CoEDTA-in the presence of 10-5 M-ACS revealed an apparent cellular Na concentration of 54-8 + 10-4 (S.E.). This was considerably in excess of the maximum amount of Na contributing to the slowest component of Na efflux from intoxicated septa. Origins of this discrepancy are considered.6. The slowest component of 22Na efflux from intoxicated septa could be markedly stimulated by increasing the external Ca concentration from a nominal 1-5 to 16 mM.The magnitude of stimulation was 44-3 + 7-8 % (S.E.). Increases in the concentration of Mg from 1-0 to 16-0 mm were without effect on the 22Na efflux.7. Application of 10-5 M-ACS produced marked depolarization of the membrane to new stable levels that lay between -10 and -20 mV.8. Washout of ACS after several hours of intoxication resulted in a partial decline in contracture tension, an acceleration of Ca efflux, little change in 22Na efflux and a repolarization of the cell membrane.

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The effect of substances releasing intracellular calcium ions on sodium‐dependent calcium efflux from guinea‐pig auricles.

Cited by 160 publications

References 39 publications

External Na-independent Ca extrusion in cultured ventricular cells. Magnitude and functional significance.

External Na-independent Ca extrusion in cultured ventricular cells. Magnitude and functional significance.

Caffeine Contracture in Frog Cardiac Muscle after Exposure to High Concentrations of Calcium

Sodium efflux in rabbit myocardium: relationship to sodium—calcium exchange

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