Single Heart Cells Research Articles

Electrophysiological properties of isolated ventricular myocytes.

There is no doubt that major advances have been made in cardiac electrophysiology using single heart cells. Accurate analysis of rapid inward sodium current and the second inward current carried by calcium has resulted in a major re-examination of the steps involved in excitation-contraction coupling in the heart. Future work using glass microelectrodes, suction pipettes and patch pipettes will yield a vast amount of information highly relevant to mechanisms involved in the initiation of the heartbeat.

Electrophysiology of single cardiac cells.

Whatever techniques of isolation one may use, it is certainly true that the isolated single heart cells are very useful in various physiological experiments. For electrophysiology, the application of the single cell serves to test findings previously obtained in the multicellular preparation. Therefore, summary and comparison of the data will become necessary in the near future. Furthermore, the application of the single cell opens new areas for electrophysiology of the heart, because when using only the single cell preparation, one can dialyse intracellular millieu and can also measure single channel analyses.

Direct effect of ouabain and diltiazem action on cultured single heart cells : T. Samoto, S. Yoneda, N. Ohte and T. Katoh. The 3rd Dep. of Internal Medicine, Nagoya City University Medical School, Nagoya, Japan

Direct effect of ouabain and diltiazem action on cultured single heart cells : T. Samoto, S. Yoneda, N. Ohte and T. Katoh. The 3rd Dep. of Internal Medicine, Nagoya City University Medical School, Nagoya, Japan

Activation of the fast transmembrane sodium current of single heart cells

Activation of the fast transmembrane sodium current of single heart cells

Inactivation of the fast sodium current across the membrane of single heart cells

Inactivation of the fast sodium current across the membrane of single heart cells

Nonspecific proteases: a new approach to the isolation of adult cardiocytes.

The potent collagenolytic activity of nonspecific proteinases suggested their use as enzymatic agents for the dissociation of single adult heart cells. This was assessed in guinea pig hearts perfused for 1 min with solutions containing hyaluronidase (100-10 000 U/mL), trypsin (100-10 000 U/mL), crude collagenase (100-500 U/mL), or nonspecific protease (0.1-100 U/mL). No rod-shaped cells were observed among the cells isolated with these concentrations of hyaluronidase, trypsin, or crude collagenase. By contrast, 45-80% of the cells released with nonspecific protease (5-10 U/mL) were rod shaped and Ca2+ tolerant. Resting and action potentials recorded from cells dispersed with nonspecific protease were similar to those recorded from cells isolated after prolonged collagenase exposure.

Reversal of current through calcium channels in dialysed single heart cells.

Calcium channels contribute to important cellular functions such as impulse conduction, rhythmic activity, muscle contraction, and secretion1 and are a major target for modulation by neurohormones and drugs2,3. Despite their importance, Ca channels are much less well understood than Na and K channels because of several problems reviewed by Hagiwara and Byerly1. First, few preparations allow good control of electrical potential and ionic composition on both sides of the membrane, yet display strong Ca currents. Second, current carried by Ca channels is often obscured by ion movements through other membrane pathways. Third, outward current flow through Ca channels, carried by Ca2+ or any other ion, has been difficult to demonstrate. This is unfortunate because measurements of the potential at which current reverses (Erev) have been crucial in understanding ion permeation and selectivity in other ionic channels (see ref. 4). In molluscan neurones, attempts at recording outward current through the Ca channel have not succeeded, largely because of overlap by nonspecific outward current5–7. In multicellular cardiac muscle preparations, strong depolarizations produce a decaying outward current that Renter and Scholz attributed to K efflux through the Ca channel8. Their interpretation is controversial, however, since the evidence leaves open other explanations for the outward current—for example, Na efflux via Na–Ca exchange9, or K efflux through K-selective channels. To overcome these problems, we studied Ca channels in single isolated heart muscle cells10–12 using a suction pipette method13. We were able to record robust Ca currents with minimal interference from other time-dependent currents while controlling potential and ion composition on both sides of the membrane. Here we present experimental evidence for a genuine reversal of ionic current through Ca channels due to outward movement of K+ ions, in support of the hypothesis of Reuter and Scholz.

Reduction of Intercellular Adhesiveness of Chick Heart Cells by Herpes Simplex Viruses 1 and 2

Infection with herpes simplex viruses type 1 or 2 prevented the aggregation of 7-day-old chick heart cells into smooth, spheroidal, spontaneously beating aggregates. Virus infection also caused a loosening of peripheral cells in aggregates formed from initially uninfected cells. Measurements of rate of attachment of labelled single heart cells to a monolayer of like cells (homotypic), to HEp-2 cells (heterotypic), or to plastic substrata (nonspecific adhesion) indicated that virus infection caused a significant but differential loss of homotypic and nonspecific adhesiveness, but no alteration in heterotypic attachment rates. These observations indicate that those cells surface changes induced by viruses which are related to cell adhesion can be quantified by techniques measuring attachment rates.

The effects of prostaglandins on the beating activity of cultured heart cells

The effects on the beating behavior of cultured rat heart cells of fourteen prostaglandins of the A, B, D, E, and F series were investigated, together with adrenaline and ouabain, at dose levels of 10 −7 and 10 −5M. Single heart cell beating activity was monitored photo-electrically and five parameters of beating behavior measured. Only PGF 2a markedly increased rate while PGF 2B reduced it. Maintenance of a stable rate (rate range) was minimally affected by prostaglandins with PGF 2β possibly reducing, and PGF 1α and 2-decarboxy E 1 possibly increasing, rate range. PGF 1α and F 2α both statistically reduced the percentage of cells beating while the other prostaglandins had no effect. Most of the prostaglandins either produced no change, or reduced, indices of contractile force (optical density changes with contractions and its first derivative (dOD/dt)). Only the negative chronotropic agent PGF 2β positive density effect. In conclusion, except for PGF 2α, prostaglandins generally have limited actions on the beating activity of cultured heart cells.

Amino acid transport by aggregates of cultured chicken heart cells. Effect of insulin.

Single heart cells dissociated from 14-day-old chicken embryos were reagregated into spheroidal clusters on a gyratory shaker and centrifuged to form cohesive discs of approximately 400 aggregates. These cultured cells accumulated 2-amino[1-14C]isobutyric acid against a gradient. When incubated for 3 hours in a protein-free, buffered, balanced salt solution, concentrative transport decreased to a stable basal level. Incubation in the presence of sodium bovine insulin prevented this fall in transport activity and resulted in increased 2-aminoisobutyric acid uptake to concentrations 40 time sthat in the medium during a subsequent 3-hour transport assay. Intracellular accumulation of 2-aminoisobutyric acid was linear during the initial 15 min of transport in the presence and absence of added insulin. Basal transport of 2-aminoisobutyric acid was temperature-dependent, requied extracellular sodium greater than 125 meg/liter, and demonstrated saturation with an apparent Vmax of 3.4 mmol/liter/10 min and an apparent Km of 2.6 mM. Basal transport activity was not reduced by cycloheximide or puromycin even after 3 hours of exposure...

Effects of Conditioning of Medium on Beating of Single Myocardial Cells In vitro

Heart cells singly dissociated from mouse embryos were cul-tured at high (4 × 105 cells per plate) or low (0.5 × 105 cells per plate) density. After cultivation for one day, the percentages of beating cells were 51 % and 75 %, respectively, and the average beating rates were 39 beats/min (b/m) and 70 b/m, respectively. The average beating rate of single heart cells cultured at low density in the medium consisting of 3 parts of conditioned medium and 1 part of fresh medium was 72-85 b/m, while the value in the fresh medium was 40-57 b/m. Lung, kidney, skeletal muscle and L cells from mice, FL cells, chick embryonic cells and reptilian iguana heart cells were effective at high density in increasing both the percentage of beating cells and the average beating rate of mouse myocardial cells cultured at low density.

Electro-optical system for monitoring activity of heart cells in culture: Application to the study of several drugs and scorpion toxins

An electro-optical system for monitoring and recording contractile activity of cultured heart cells is described. The system is based on the use of a commercially available electro-optical displacement follower aimed at the image of a cell membrane-medium interface viewed on a television screen. The system allows the continuous recording of rate, amplitude and rhythm of contractions of single or clustered heart cells. Cultures of heart cells obtained from 11-day chick embryos were used to test the activity of several pharmacological agents including adrenoceptor stimulants, calcium channel-blocking agents, ouabain, tetrodotoxin and scorpion toxins.

Measurement of the rate and velocity of movement by single heart cells in culture

A new method for the quantification of velocity of movement of single muscle cells in culture is described. The method involves television monitoring of microscope images and video analysis to yield data in chart form. Recorder printout is linearly related to distance of cell movement. Two new modifications of techniques for measuring the number of muscle cell movements are also described. These include television video analysis and a light-sensitive field effect transistor (Photo-fet). Application of both techniques to the measurement of contractions of single beating heart cells is shown, and the chronotropic effect of norepinephrine is monitored with increasing concentrations of the drug. Application of video analysis to the inotropic effect of the same drug also is studied, and quantitative data for velocity of contraction and relaxation are determined in microns per second.

Development of sensitivity to tetrodotoxin in beating chick embryo hearts, single cells, and aggregates.

The spontaneous activity of intact embryonic heart becomes progressively more sensitive to tetrodotoxin block with increasing age of the embryo. The activity of isolated single heart cells in culture was relatively insensitive, independent of embryo age. Aggregates formed from single cells responded to tetrodotoxin in the same manner as intact hearts; aggregated cells from older hearts were sensitive.

The Effect of Acetylcholine on Single Embryonic Chick Ventricle Cells

SummaryThe effect of acetylcholine on the beating rate of single chick embryo heart cells cultured from 8 to 10 day ventricles was determined using a new television monitor optical system. Acetylcholine had a clear negative chronotropic effect on these cells, with a threshold at 10-8-10-7 g/ml. The slowing in beating rate after the addition of acetylcholine was reversible, and was not associated with any detectable change in the inotropic state of the cells. These findings are consistent with the effect of acetylcholine on non-cultural chick embryo ventricular tissue of the same age.

Effect of low temperature on single heart cells from an adult hibernator and non-hibernator

Rhythmically contracting single heart cells from adult thirteen-lined ground squirrels ( Citellus tridecemlineatits, a hibernator) and white rats ( Rattus norvegiens, a non-hibernator) were obtained by treatment with trypsin and collagenase. The effect of low temperature was tested in these preparations. In contrast to isolated whole hearts, there was no difference in the response of the single cells from the two species, for some cells in each group continued to beat at 0 °C.