Influences of sodium and calcium on the recovery process from potassium contracture in the guinea‐pig taenia coli

SUMMARY1. To investigate the mechanism of generation of contractions in tissues from the guinea-pig stomach, the effects of caffeine, procaine, acetylcholine (ACh), diltiazem or MnCl2 on the contraction evoked from small bundles of intact or skinned muscles (50 ,um in width and 250-300 ,um in length) were observed.2. All these agents except for ACh blocked the spontaneously generated contraction. Diltiazem (1 x 10-4 M) had no effect and MnCl2 (3 mM) slightly reduced and caffeine enhanced the tonic contraction evoked in Na-free solution, whereas procaine relaxed the tissue. On the other hand, in the isotonic [K]0 solution, diltiazem, MnCl2 and procaine relaxed the tissue, while caffeine enhanced the tonic contraction.3. Under pre-treatment with Ca-free solution (2 mM-EGTA-containing solution) after depletion of the stored Ca, application of 2-5 mM-Ca and subsequently applied 5 mM-caffeine produced contractions (Ca-and caffeine-induced contractions, respectively). In polarized (5-9 mM-K.) and depolarized (128 mM-KO) muscles, the various agents simultaneously applied with 2-5 mM-Ca modified the amplitude of the Ca-induced and the resulting caffeine-induced contractions. Thus, at least three different Ca influxes required to evoke the Ca-or caffeine-induced contraction were identified; diltiazem-sensitive Ca influx, diltiazem-insensitive but Mn-sensitive Ca influx and Mn-insensitive Ca influx.4. The Ca-and caffeine-induced contractions in Ca-free and 15-5 mM-Na-containing solutions were gradually reduced in amplitude, in proportion to the time of exposure. However, amplitude of the caffeine-induced contractions was inhibited to a greater extent and the duration of the contracts was less prolonged than the case of the Ca-induced contraction.5. In saponin-treated skinned muscles, the minimum concentration of Ca required to produce the contraction was 1 x 10-7 M, and the maximum contraction was evoked by application of 1 x 10-5 M-Ca. The effects ofNa-free solution on the Ca accumulation and release to and from the storage site were also observed in these skinned muscles.

Section: Discussionmentioning

confidence: 80%

Effects of calcium and manganese ions on mechanical properties of intact and skinned muscles from the guinea‐pig stomach

Itoh

Kuriyama

Nanjo

1982

“…The ability of [Na]0 to relax the contracture induced by Na-free solution was too rapid to be accounted for on the basis of the observed decrease in the 45Ca content in the cells ofthe guinea-pig taenia coli on the readmission of [Na]o which was relatively slow. Furthermore, Katase & Tomita (1972) have shown that a dose of 7 mM-[Na]0 is sufficient to relax the contracture maintained in Na-free solution. Although a direct comparison was impossible because of the different experimental conditions, the addition of 7 mM-[Na]o slightly activated the 45Ca efflux.…”

Section: Residual 45ca Effluxmentioning

confidence: 99%

“…In the taenia coli of the guinea-pig, Katase & Tomita (1972) observed that tissues initially contracted in high K solution remained contracted when [K]o was reduced to normal in Na-free (sucrose) solution, but would then relax on re-addition of Na, and more recently, Brading (1978) has also reported evidence suggesting some involvement of the Na gradient in transmembrane Ca movement in this tissue, and Brading & Widdicombe (1976) have demonstrated a [Na]0-dependent Ca efflux and a [Na]i-dependent Ca uptake in intact tissues.…”

Section: Introductionmentioning

confidence: 99%

Effects of external cations on calcium efflux from single cells of the guinea‐pig taenia coli and porcine coronary artery.

Hirata¹,

Itoh²,

Kuriyama³

1981

SUMMARY1. Single smooth muscle cells were prepared from the guinea-pig taenia coli and the porcine coronary artery by treatment with collagenase, in order to measure the 45Ca flux with special reference to the effects of external cations.2. In excess [K]o solution, cell suspensions prepared from both tissues showed an increased 45Ca uptake within 3-5 min. In Na-free solution, the cells prepared from taenia coli, but not from coronary artery showed an increased 45Ca uptake. The Ca uptake of the cells paralleled with the tension increase recorded from tissues of both species.3. The efflux of 45Ca into Ca-free EGTA containing solution was markedly increased by [Na] 7. In cells from the taenia coli, 45Ca efflux could still be observed in nominally Naand Ca-free solution. This residual 45Ca efflux made a large contribution to the total 45Ca efflux.8. When 45Ca uptake was measured in Na-free (Tris) solution, the [Na]o-activated, [Ca]o-activated and residual 45Ca effluxes of cells from the taenia coli were accelerated, non-selectively.9. These results obtained with cells prepared from the guinea-pig taenia coli are comparable to the Ca2+ efflux mechanism seen in the squid axon. However, maintenance of low concentrations of [Ca]i seems to require not only the above three 45Ca efflux mechanisms, but also Ca sequestering mechanisms in the cell.0022-3751/81/3240-0912 $07.50

“…P. AARONSON AND C. VAN BREEMEN DISCUSSION Sucrose was chosen as the primary Na substitute in this study for several reasons. This compound does not penetrate the cell membrane (Casteels, 1970), and its substitution for Na does not cause a membrane depolarization, which might itself influence transmembrane Ca fluxes (Katase & Tomita, 1972). Sucrose appears not to cause the kind of gross damage to the cell membrane which would be evidenced by an increase in the sorbitol space (Fig.…”

Section: P Aaronson and C Van Breemenmentioning

confidence: 99%

Effects of sodium gradient manipulation upon cellular calcium ⁴⁵Ca fluxes and cellular sodium in the guinea‐pig taenia coli

Aaronson

Breemen

1981

SUMMARY1. Sucrose and choline were utilized as NaCl substitutes in order to investigate Na-Ca interactions in the smooth muscle of the guinea-pig taenia coli.2. Progressive substitution of NaCl by sucrose caused a progressive increase in cellular exchangeable Ca. This uptake, which amounted to about 300 smole Ca/kg tissue upon total Na replacement, reached a plateau within 20 min. Complete substitution of NaCl by choline chloride caused cellular Ca to increase rapidly to an initial peak, and then decrease to a stable plateau which was also about 300 ,umole/kg above control.3. Replacement of NaCl by either sucrose or choline chloride caused a transient increase in the Ca influx rate, which was measured using a 3 min pulse labelling with 45Ca. This increase was more pronounced in choline chloride.4. NaCl substitution by either sucrose or choline chloride caused a decrease in the 45Ca efflux rate. Two exponential components of transmembrane 45Ca efflux were found in control and Na-free media.5. Treatment of tissues with 3 x 10-5 M-ouabain did not significantly affect the cellular Ca content after 80 min, at which time the Na and K gradients were largely dissipated.6. Removal of medium K caused a slower dissipation of the Na and K gradients. This treatment decreased cellular Ca, did not affect the Ca influx rate, and increased the 45Ca efflux rate.7. Tissues were incubated in depolarizing media containing 10-4 M-ouabain in order to remove the Na gradient. Subsequent measurement of cellular Na indicated the absence of a significant fraction of bound Na.8. The ratio [Na]o/[Na]i had a value of 6-3 in control medium, and decreased as [Na]o was progressively lowered by sucrose substitution, reaching a value of < 1 in a medium containing 5 mm-Na.9. These experiments provide evidence that a Na-Ca exchange carrier does not play an important role in regulation of tension in this muscle, and also indicate that the Ca gradient is not solely dependent on the Na gradient in guinea-pig taenia coli.