Voltage clamp of bull‐frog cardiac pace‐maker cells: a quantitative analysis of potassium currents.

Giles, Wayne R.; Shibata, Erwin F.

doi:10.1113/jphysiol.1985.sp015857

Cited by 101 publications

(76 citation statements)

References 58 publications

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“…These 'isochronal' current-voltage relationships give a good estimate of the inward rectifier current IK1, since the delayed rectifier current in these cells, IK' has a much slower onset (Hume et al, 1986). This assumption is borne out by the fact that the plots of the CVRs that we obtained showed a prominent inward rectification, as is typical of this current in frog atrial cells (Giles & Shibata, 1985). It was found that aluminium caused small but consistent outward shifts in the current level at membrane potentials positive to -60 or -50 mV.…”

Section: Transmembrane Ionic Currentssupporting

confidence: 52%

“…Single frog atrial cells were isolated by a method described in Giles & Shibata (1985): 1 x 1 mm atrial pieces were cut into a Ca-free Ringer solution. Two enzyme solutions were then added sequentially.…”

Section: Single Cell Experimentsmentioning

confidence: 99%

“…These were prepared by the methods of Giles & Shibata (1985). Briefly, rabbit hearts were perfused retrogradely through an aortic cannula on a Langendorff apparatus.…”

Section: Single Cell Experimentsmentioning

confidence: 99%

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Effects of aluminium on electrical and mechanical properties of frog atrial muscle

Meiri

Shimoni

1991

British J Pharmacology

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The effects of aluminium on membrane ionic currents were studied in single cardiac myocytes. Most of the work was done on frog atrial cells, but some experiments were also carried out on single cells isolated from rabbit ventricles and atria. The effects of aluminium on the force of contraction of frog atrial trabeculae were also investigated. Aluminium was prepared from AlCl3 as a stock 0.5 m solution which has a pH of 3.5. Before each experiment, this solution was added to the control solution, to give a final concentration of 20–100 μg ml−1 aluminium (0.75–3.75 mm AlCl3). The solutions were brought to a pH of 7.4 or 7.6, at which they consist of a mixture of amorphous aluminium hydroxides and a very small amount of soluble ionic aluminium complexes: free aluminium cations (less than 10 pm), aluminohydroxide anions (less than 8 μm). The addition of this suspension reduced the peak inward calcium currents in single rabbit atrial and ventricular cells and in frog atrial cells. In the latter, the peak current was reduced (at + 10 mV) to 45% of control (mean of 9 cells). This effect was reversible upon washout, and was obtained at all membrane potentials, with no shift of the calcium current voltage relationship along the voltage axis. Aluminium also reduced the time‐dependent potassium current IK. This reduction was observed at all membrane potentials. For example, at + 10 mV, the mean reduction of IK (n = 9) was to 69% of the control amplitude. This effect, which was very difficult to reverse, was not due to IK rundown. The fully activated current‐voltage relationships (obtained by standard ‘tail’ analysis) showed that the effect of aluminium was due mainly to a decrease in conductance and not to a shift in the activation range of IK. The mean voltage of half activation was shifted by 8 mV in the depolarizing direction (n = 5). The background potassium current IK1 was also slightly but consistently changed in a complex fashion, with an outward shift at membrane potentials positive to −60 mV. For example, at a membrane potential of −40 mV, the mean shift was by 22 ± 4 pA. At more negative potentials, there was an inward shift in the current amplitudes. For example, for steps to −100 mV the current elicited was larger (more inward) by 53 pA (mean value, n = 10). The reversal potential was slightly shifted (< 10 mV) in the hyperpolarizing direction. The force of contraction of frog atrial trabeculae was altered by aluminium in a complex manner, which showed marked seasonal variation. During most of the year, 50–100 μg ml−1 aluminium caused a biphasic change, with an early small and consistent decrease, followed by a large increase in twitch amplitude. For a short period corresponding to the (local) winter months the sensitivity to aluminium was greatly enhanced. Aluminium 100 μg ml−1 totally abolished contraction (n = 5), while a lower concentration (20 μg ml−1) produced a sustained reduction in the force of contraction. Similar biphasic and seasonal responses have been reported to be induced by lanthanum. The biph...

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Section: Transmembrane Ionic Currentssupporting

confidence: 52%

Section: Single Cell Experimentsmentioning

confidence: 99%

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Effects of aluminium on electrical and mechanical properties of frog atrial muscle

Meiri

Shimoni

1991

British J Pharmacology

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“…4 (Giles & Shibata, 1985;DiFrancesco et al 1986; Ginneken & Giles, 1991) -25 mV, suggesting that If is carried by more than one ion species. Similar results were found in a total of ten experiments.…”

Section: Voltage Dependence Of If Activationmentioning

confidence: 99%

Properties of the pacemaker current (If) in latent pacemaker cells isolated from cat right atrium.

Zhou

Lipsius

1992

The Journal of Physiology

106

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SUMMARY1. Single latent pacemaker cells were isolated from the Eustachian ridge of cat right atrium using Langendorif perfusion and enzyme dispersion techniques. Wholecell patch-clamp techniques were used to study the hyperpolarization-activated inward current (If).2. All cells studied beat rhythmically. Pacemaker activity was recorded in the voltage range -68 +1 to -54 + 2 mV and its cycle length was 901 + 67 ms (72 + 5 beats min-) at 34-36 'C. Cells were elongated with tapered ends, and appeared bent or crinkled without obvious striations. Mean cell diameter and length were 7-4+05,tm and 93-1 +5-9 jtm, respectively (n = 15). Input resistance and total membrane capacitance were 22 +02 GQ and 27-8 + 3-1 pF, respectively.3. Hyperpolarizing clamp steps more negative than -50 mV elicited a timedependent increasing inward current that was maximally activated at -120 mV.

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“…When expressed by microinjection of RNA into Xenopus oocytes, it induces a slow, voltagedependent K+ current that closely resembles the delayedrectifier K+ current expressed from uterine poly(A)+ mRNA isolated from ovariectomized, diethylstilbestrol (DES)-treated rats (12,13). Both of these currents also bear a strong resemblance to the classical delayed outward rectifier (IV,), the main repolarizing K+ conductance in the cardiac ventricle (14,15). To our knowledge, the nature of the proteins underlying these delayed rectifier K+ currents in heart and uterus has not been determined previously.…”

mentioning

confidence: 99%

Cloning and expression of the delayed-rectifier IsK channel from neonatal rat heart and diethylstilbestrol-primed rat uterus.

Folander

Smith

Antanavage

et al. 1990

Proc. Natl. Acad. Sci. U.S.A.

174

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cDNAs encoding a delayed-rectifier-type K+ channel were cloned from both neonatal rat heart and ovariectomized, diethylstilbestrol-primed rat uterus by using the polymerase chain reaction. (12,13). Both of these currents also bear a strong resemblance to the classical delayed outward rectifier (IV,), the main repolarizing K+ conductance in the cardiac ventricle (14, 15). To our knowledge, the nature of the proteins underlying these delayed rectifier K+ currents in heart and uterus has not been determined previously.In this report, we describe the cloning and expression of the (18,19). Oligonucleotides (20-mers to 60-mers) were synthesized on an Applied Biosystems model 380B DNA synthesizer with /3-cyanoethylphosphoramidite chemistry.Cloning of K+ Channel cDNAs. PCR was used to clone cDNAs from the poly(A)+ fraction of mRNAs isolated from neonatal rat heart, ovariectomized and DES-primed rat uterus, and adult rat kidney (20). The oligonucleotide used to prime the first-strand cDNA synthesis was derived from the kidney lsK cDNA sequence (10) and was complementary to the sense strand, 18-42 bases downstream of the protein coding region (nucleotides 408-431 in Fig. 2). The first-strand cDNA was then used directly in the PCR. An upstream oligonucleotide primer was constructed that contained a phage T7 promoter (5'-TAATACGACTCACTATAGG-GAGA-3'; ref. 21) followed by a sequence located upstream of the coding region in the IsK cDNA (from nucleotides -40 to -19 in Fig. 2). The PCR was performed for 40-50 cycles of 1-min strand separation at 94°C, 2-min hybridization at 56°C, and 3-min extension at 72°C. Reaction products of the expected size [-450 base pairs (bp)] were isolated by preparative gel electrophoresis and cloned into pUC13 by standard techniques. Nucleotide sequences of the clones were determined by the chain-termination method (22) with a Abbreviations: DES, diethylstilbestrol; PCR, polymerase chain reaction.

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Voltage clamp of bull‐frog cardiac pace‐maker cells: a quantitative analysis of potassium currents.

Cited by 101 publications

References 58 publications

Effects of aluminium on electrical and mechanical properties of frog atrial muscle

Effects of aluminium on electrical and mechanical properties of frog atrial muscle

Properties of the pacemaker current (If) in latent pacemaker cells isolated from cat right atrium.

Cloning and expression of the delayed-rectifier IsK channel from neonatal rat heart and diethylstilbestrol-primed rat uterus.

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