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

Hirata, Masato; Itoh, Takeo; Kuriyama, Hirosi

doi:10.1113/jphysiol.1981.sp013552

Cited by 49 publications

(20 citation statements)

References 29 publications

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“…It has therefore been suggested that in heart Na+/Ca2 + exchange could contribute not only to Ca2 + extrusion during relaxation but also to Ca2 + entry during depolarization. In intact cells from the taenia coli, Hirata et al (1981) found that the Na +-activated Ca2 + efflux was related to the square of NaO+ concentration and was independent of membrane potential. They concluded that the exchange was electroneutral in smooth muscle.…”

Section: Discussionmentioning

confidence: 97%

“…+ concentration (Casteels & van Breemen, 1975). Interestingly, the physiological importance of Na+/Ca2+ exchange may vary according to the type of smooth muscle, as illustrated by the findings by Hirata et al (1981). They showed that this Ca2 +-extrusion system was absent from single cells prepared from the pig coronary artery, whereas it was operative in cells from the guinea-pig taenia coli.…”

Section: Discussionmentioning

confidence: 99%

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Sodium/calcium exchange in smooth-muscle microsomal fractions

Morel¹,

Godfraind²

1984

Biochemical Journal

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1. The existence of Na+-dependent Ca2 + transport was investigated in microsomal fractions from the longitudinal smooth muscle of the guinea-pig ileum and from the rat aorta, and its activity was compared with that of the plasmalemmal ATPdependent Ca2+ pump previously identified in these preparations. 2. The rate of Ca2 + release from plasmalemmal vesicles previously loaded with Ca2 + through the ATP-dependent Ca2 + pump was transiently faster in the presence of 150 mM-NaCl in the medium than in the presence of 150mM-KCl or -LiCl or 300mM-sucrose. 3. Na+-loaded vesicles took up Ca2 + when an outwardly directed Na+ gradient was formed across the membrane. The Ca ionophore A23 187 induced a rapid release of 85% of the sequestered Ca2 +, whereas only 15% was displaced by La3 +. Ca2 + accumulated by the Na + -induced Ca2 + transport was released by the addition of NaCl, but not KCI, to the medium. 4. Ca2 + uptake in Na+-loaded vesicles was inhibited in the presence of increasing NaCl concentration in the medium. Half-maximum inhibition was observed with 28 mM-NaCl. Data fitted the Hill equation, with a Hill coefficient (h) of 1.9. 5. Na +-induced Ca2 + uptake was a saturable function of Ca2 + concentration in the medium. Half-maximum activity was obtained with 18 M-Ca2+ in intestinalsmooth-muscle microsomal fraction and with 50,uM-Ca2 + in aortic microsomal fraction. 6. The results suggest that in these membrane preparations a transmembrane movement of Ca2+ can be driven by a Nal gradient. However, the Na+-induced Ca2 + transport had a lower capacity, a lower affinity and a slower rate than the ATP-dependent Ca2 + pump.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Sodium/calcium exchange in smooth-muscle microsomal fractions

Morel¹,

Godfraind²

1984

Biochemical Journal

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“…In Ca-free solution, applications of Ca produced the contraction after depletion of the stored Ca in the stomach, whereas no contraction occurred in the mesenteric ahd coronary arteries (Itoh et al 1981 b;Hirata, Itoh & Kuriyama, 1980). In the stomach muscle tissue, the influx of Ca may directly activate the contraction.…”

Section: Discussionmentioning

confidence: 99%

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

Itoh

Kuriyama

Nanjo

1982

The Journal of Physiology

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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.

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“…Measurement of release of Ca from the store site Suspensions of isolated smooth muscle cells were prepared by enzymic digestion (collagenase 607 T. HASHIMOTO AND OTHERS 2 mg/ml, Worthington Biochemicals, CLS type 3; trypsin inhibitor 0 5 mg/ml, Sigma type I-S; bovine serum albumin 2 mg/ml, Sigma Fraction V) of the dog mesenteric artery for 1 h at 36 0C as described by Hirata, Itoh & Kuriyama (1981). To investigate the effects of InsP3 on the Ca stored in cells, the cells were skinned by saponin as described previously (Suematsu et al 1984).…”

Section: Methodsmentioning

confidence: 99%

Inositol 1,4,5‐trisphosphate activates pharmacomechanical coupling in smooth muscle of the rabbit mesenteric artery.

Hashimoto¹,

Hirata²,

Itoh³

et al. 1986

The Journal of Physiology

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225

103

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SUMMARY1. To clarify the nature of the noradrenaline (NA)-induced contraction, the effects of NA on inositol phospholipid metabolism and the actions of inositol 1,4,5-trisphosphate (InsP3) on skinned muscle of the rabbit mesenteric artery were investigated.2. NA, in concentrations over 1 nm, reduced the amount of phosphatidylinositol 4,5-bisphosphate (PI-P2) and increased the amount of phosphatidic acid (PA). The maximum reduction in the amount of PI-P2 and the maximum increase in the amount of PA were observed in the presence of 1 /LM-NA. With prolonged application of NA, the PI-P2 was gradually restored to near the control level, but with repeated applications of NA separated by rinses with Krebs solution, there was a consistent reduction of PI-P2.3. The NA-induced PI-P2 breakdown was inhibited by the ax-adrenoceptor blocking agent, prazosin.4. After incubation of the tissue with radioactive inositol-containing solution, NA transiently increased the amount of radioactive InsP3 which was followed by increases in the amount of inositol 1,4-bisphosphate (InsP2) and inositol monophosphate (InsP).5. After accumulation of Ca by saponin-treated muscle cells of the dog mesenteric artery dispersed by collagenase, InsP3 released Ca stored in cells but InsP2 did not. A23187 (5/M) but not InsP3 (up to 10 tM), depleted Ca accumulated in the presence of ATP.6. In saponin-treated skinned muscle tissues, InsP3 in concentrations over 0 3 ,UM, produced contraction following accumulation of Ca into the store site. InsP3 released Ca from the same source as caffeine. The release of Ca by InsP3 appeared in a concentration-dependent manner and this release also depended on the amount of Ca stored in cells (the median effective dose (ED50) was 3 0 /tM in 0-1 tM-Ca and 1-0/tM in 0-3 /tM-Ca).7. We concluded that NA activates ax-adrenoceptors, thus hydrolysing P1-P2 and synthesizing InsP3. This product can release Ca stored in cells as estimated from the contraction in skinned muscle tissues, and also reduces the residual amount of Ca T. HASHIMOTO AND OTHERS stored in skinned dispersed muscle cells. Contraction evoked by NA through pharmacomechanical coupling can be explained as a function of InsP3.

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

Cited by 49 publications

References 29 publications

Sodium/calcium exchange in smooth-muscle microsomal fractions

Sodium/calcium exchange in smooth-muscle microsomal fractions

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

Inositol 1,4,5‐trisphosphate activates pharmacomechanical coupling in smooth muscle of the rabbit mesenteric artery.

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