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S Sunano

Publications and source records attributed to S Sunano.

At least 91 records · Page 5Linked to original sources
PubMed1980

Comparison of effects of low temperature and metabolic inhibition on high-K induced contracture of vas deferens.

The effects of temperature on high-K induced contracture of guinea-pig vas deferens were studied and compared with those of metabolic inhibitions. The rate of rise and fall of the phasic contraction decreased with the decrease in temperature. At 5 degrees C, the time to peak tension and half relaxation time increased to 25 times and to 38 times of those observed at 35 degrees C, respectively. The height of the phasic contraction increased by lowering of the temperature. The height of the tonic contraction also increased by lowering the temperature down to 15 degrees C but then decreased. Glucose removal and anoxia showed no effect on the phasic contraction, whereas the tonic contraction was abolished by these treatments. Metabolic inhibitors such as DNP, NaN3 or KCN, caused the depression of both the phasic and tonic contractions, being more effective on the tonic contraction. The tonic contraction was abolished before the phasic contraction was depressed by 50%. The time to peak tension and half relaxation time were not affected by metabolic inhibitions. These results suggest that low temperature causes the reduction in the rate of contractile reaction of muscle protein and in the rate of Ca accumulation and/or of Ca extrusion. Metabolic inhibition, on the other hand, caused reduction in the energy supply for the contraction and brought about depression of the contraction.

Animals↗
PubMed1980

[Contraction of rabbit cerebral artery caused by elevated K+ in vitro (author's transl)].

1. When the blood from rabbit or from human was subjected to hemolysis in the test tubes, K-concentration of serum was elevated to about 40 mEq/l. According to these result, the effects of K ion of the concentration up to 30 mM on the contractile response were studied. 2. When the K-concentration was elevated to 10 mM or 20 mM, a transient relaxation was observed. The relaxation, however, was transient and reversed into contraction. No relaxation was observed when K-concentration was elevated gradually. 3. Basilar artery showed higher sensitivity than carotid artery to the elevation of extracellular K-concentration and showed a contractile response to lower K-concentration. Sensitivity to noradrenaline, on the other hand, was lower than that of carotid artery. 4. The contraction by K was stronger in the preparation which showed spontaneous contractions. The contractile response to K was abolished by Ca removal, verapamil (10(-5) M), La (10(-4) M) or Mn (2 mM). 5. Phentramine (2 x 10(-5) M) depressed the contractile response. TTX (5 x 10(-7) g/ml), atropine(10(-6) M) or methysergide (5 x 10(-5) M) showed no effect on the contraction by K. It was suggested that, although the contractile response to elevated K may be due, in part, to the released cathecholamine, it was caused mainly by the direct action of K, especially by its depolarizing action. Since the action was stronger in the preparation which showed spontaneous contraction, the spike activity, in addition to the depolarization, might have important role for this contraction. The contraction may be brought about by influxed Ca caused by the depolarization and/or action potential (Ca spike). It was also suggested that this effect can be one of the cause of the spasm of cerebral blood vessels.

Animals↗
PubMed1978

The role of membrane electrical activities and extracellular calcium in high-K-induced contracture of guinea pig ureter.

Electrical and mechanical activities in high-K-induced contracture of guinea pig ureter and taenia coli were studied using the sucrose-gap method. Ureter immersed in high-K solution showed a contracture consisting of three components as well as twitch contractions evoked by a few spikes which were observed during the depolarizing phase. Reapplication of high-K solution after a short washing procedure with normal solution induced a contracture composed of only the first and the third components. No action potential was observed during the course of membrane depolarization by this procedure. High-K-induced contracture was highly sensitive to extracellular Ca: no tension development of the ureter despite the membrane depolarization was observed in Ca-free high-K solution. The addition of Ca to Ca-free high-K solution caused a contracture similar to that by high-K solution in the presence of Ca. Verapamil (10(-5) M) blocked all three components, leaving only slightly depressed twitch contractions initiated by action potentials. The possibility that all of these components of high-K-induced contracture were initiated by influxed Ca from extracellular space was also strengthened.

Animals↗
PubMed1977

[Effects of dantrolene sodium on some types of visceral muscles (author's transl)].

Twitch contraction height of the outer layer of esophagus was reduced by 5 X 10(-6) g/ml of dantrolene to 7% of the height observed before the application. High-K induced contracture of this preparation and of cremaster muscle were also depressed to 14% and to 18% of the control, respectively. When dantrolene (25 X 10(-6) g/ml) was applied during the contracture induced by 9.7 X 10(-4) g/ml of caffeine, a complete relaxation was observed. Dantrolene had no effect either on the evoked twitch contraction of the smooth muscle of vas deferens or on spontaneous contractions of the taenia coli. High-K induced contracture of these smooth muscles was not affected by dantrolene. Electron micrograph showed that the outer layer of esophagus and cremaster muscle were composed of striated muscle cells in which the sarcoplasmic reticulum, transverse tubulus, and triadic junctions were well developed. In smooth muscle preparations, although sarcoplasmic reticula were observed, neither transverse tubula nor triadic junctions comparable to those in the striated muscle were evident. These morphological differences may explain differences in the action of the drug.

Animals↗
PubMed1976

High-potassium induced contracture in guinea pig ureter.

Some characteristic properties of guinea pig ureter in high-K induced contracture were studied. The contracture was composed of three contraction components, quick-phasic, slow transient, and substained states. The height of the second component decreased with time when the preparation was immersed in high-K solution. This was observed during a brief washing treatment with normal Tyrode solution applied at varius times after immersion in high-K solution. When the brief washing treatment was applied after 30 min, a contracture composed of the first and the third components was observed. Similar results were obtained in Ca-induced contracture of K-depolarized preparations. Fluctuations of tension were observed in the course of the contracture. The fluctuations could be evoked by various types treatments and were observed to have some relationship to extracellular Ca. It was indicated that extracellular Ca has an important role in the initiation of each component of the contracture and that the role of Ca is controlled by the cell membrane.

Animals↗