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Volume 101 (1993)
- Issue 6 Pages 349-
- Issue 5 Pages 289-
- Issue 4 Pages 197-
- Issue 3 Pages 101-
- Issue 2 Pages 59-
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Volume 101, Issue 3
Displaying 1-9 of 9 articles from this issue
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Kazutaka MOMOSE1993 Volume 101 Issue 3 Pages 101-110
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSIn studies on the intrinsic contraction mechanisms of smooth muscle, various factors such as cell-to-cell interaction, penetration of chemicals to the trigger regions, or extracellular spaces in the tissue may influence the results. The use of single smooth muscle cells in such investigations may help to eliminate these factors. Single smooth muscle cells can be isolated from guinea pig taenia coli by digesting the minced tissue with a combination of collagenase and soybean trypsin inhibitor. The cells are spindle shaped, 100-200 μm in length and 10μm in diameter. Three kinds of techniques for determination of contractile responses of single smooth muscle cells have been established: 1) fixation method, 2) perfusion method, and 3) capillary adhesion method. Using these techniques, the cells appeared to be contracted in a dose-dependent manner (graded response), while another mode of the contractile response, the “all-or-none response”, has also been proposed. Scanning and transmission electron micrographs of the single cells revealed several evaginations of various sizes and shapes on the surface and electron dense bodies at the neck of the evaginations. ED50 obtained with the single cells, prepared from taenia coli of guinea pigs with collagenase in the presence of trypsin inhibitor was similar to that obtained with the intact tissue. Digestion of the tissue with highly purified collagenase and papain yields a large number of single cells with higher sensitivity to agonists. Characteristics of cells isolated from ileal longitudinal muscle of guinea pig are similar to those of cells isolated from taenia coli. The magnitude of contraction and sensitivity to acetylcholine were different in each cell. Incubation of isolated tissues with various concentrations of agonists followed by measurement of cell length in the tissue showed that the heterogeneous responses of the cells were intrinsic characteristics of smooth muscle cells and not due to damage incurred during the isolation procedure. Since isolated smooth muscle cells possess contractility, these might preserve the characteristics of smooth muscle, so they can be used for smooth muscle research. It must be considered, however, that each cell in the smooth muscle tissue has different contractility.View full abstractDownload PDF (26348K) -
Issei TAKAYANAGI, Mitsutoshi SATOH, Katsuo KOIKE1993 Volume 101 Issue 3 Pages 111-122
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSSmooth muscle tissues were contracted by excitation of each muscle cell. Single cells prepared from guinea pig taenia caecum and trachea were contracted by extracellular application of acetylcholine and/or carbachol, whose concentrations were the same as those in the tissues. The concentration-response curve was shifted in a parallel fashion by competitive antagonists. The pA2-values of the antagonists were in good agreement with those estimated using the intact tissue. The apparent dissociation constants of cholinergic drugs estimated from inhibition of the specific binding of [3H] QNB (quinuclidinyl benzilate) to the single cells by the cholinergic drugs were also in agreement with the values in other membrane preparations. Similar findings were obtained in the single cells, microsomal fractions and isolated tissues from the guinea pig tracheal smooth muscles. In rabbit aortic single cells, the existence of two pharmacologically distinct α1-adrenoceptor subtypes, α1A and α1B, in vascular smooth muscle cells was supported. Furthermore, the amount of prostaglandin F2α released from guinea pig tracheal single cells was increased through activation by α2-adrenoceptor agonists. The amount of prostaglandin F2α released by norepinephrine decreased with age, while the total amount of α2-adrenoceptors and the dissociation constants of the α2-adrenergic drugs from the receptor did not change. The relaxation induced by β-adrenoceptors did not alter with age. The total amount of β-adrenoceptor and the dissociation constants of β-adrenergic drugs from their receptor did not alter with age. An excellent relationship between the potency of isoprenaline and the maximum binding of [3H] dihydroalprenolol estimated in the single cells from 6- to 40-week-old guinea pigs was found, suggesting that the increase in the potency of isoprenaline is due to the increase in the maximum binding. The value in the single cells from 100-week-old guinea pigs deviated significantly from the regression line. This result suggests that the decrease in potency in the single cells from 100-week-old animals is due to a change in post β-receptor processes in responsiveness. The smooth muscle single cells are useful for the study of drug-receptor interactions. Furthermore, post-receptor processes in responsiveness were discussed.View full abstractDownload PDF (19648K) -
Mitsuo MITA, Kazuhiko OISHI, Takao HASHIMOTO, Masaatsu K. UCHIDA1993 Volume 101 Issue 3 Pages 123-131
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSMost isolated smooth muscle cells from guinea pig taenia caecum responded repeatedly, showing an all-or-none response to acetylcholine (ACh). However, the average responses of all the cells were graded owing to the difference in the threshold concentration of ACh, like that of whole tissue. The sensitivity of the muscarinic receptor on individual cells was the same as that of whole tissue and ACh bound to the receptor concentration-dependently. The shortening of the cells in response to ACh depended upon the influx of extracellular Ca2+ through the Ca channel. 45Ca2+ influx stimulated by ACh was very sharp and highly correlated with the shortening of the cells. The shortening of α-toxin-permeabilized smooth muscle cells was induced by increasing free Ca2+. The concentration-response relationship to free Ca2+ had a very steep slope, and the shortening appeared to be an all-or-none response rather than a graded response. In conclusion, it is suggested that isolated smooth muscle cells show an all-or-none response as a result of a slight increase in the intracellular free Ca2+ level over the threshold concentration when early signalling coupled to ACh-receptor stimulation reaches the threshold to evoke Ca2+ influx and Ca2+ release.View full abstractDownload PDF (18204K) -
Masamitsu IINO, Toshiko YAMAZAWA, Makoto ENDO1993 Volume 101 Issue 3 Pages 133-142
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThis paper briefly reviews our current effort to study the Ca2+ mobilization mechanism in enzymatically dispersed single smooth muscle cells. Each single cell obtained from guinea pig taenia caeci possesses two types of Ca2+ stores, one (Sα) with both Ca2+-induced and IP3-induced Ca2+ release mechanisms and the other (Sβ) with only IP3-induced Ca2+ release mechanism. After depletion of Sα either with ryanodine treatment or with caffeine pretreatment, carbachol failed to induce Ca2+ release, while intracellular application of IP3 did induce Ca2+ release. Our results suggest that the difference between the agonist and IP3-induced responses can be resolved by obligatory involvement of positive feedback control of IP3-induced Ca2+ release in the agonist-induced Ca2+ release. Furthermore, we were able to demonstrate that the dose-response relation in single cells shows an all-or-none feature, which seems at least partly due to the feedback control of Ca2+ release. We discuss the reasons why graded dose-response relation is obtained in bundles of smooth muscles, while the response of single cells is an all-or-none type.View full abstractDownload PDF (16249K) -
Kazuo OBARA, Hideyo YABU1993 Volume 101 Issue 3 Pages 143-151
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThe voltage-dependent Ca2+ channels (VDC) in smooth muscle cell membranes are the major pathway by which Ca2+ enters the cell during contraction. It has been reported that VDC can be modulated by reversible channel protein phosphorylation and dephosphorylation reactions. In intestinal smooth muscle cell, muscarinic agents have been reported to increase the break-down of phosphatidylinositol 4, 5-bisphosphate, which indicates that inositol-1, 4, 5-trisphosphate and diacylglycerol (DG) can be generated. DG activates protein kinase C. Carbachol (CCh), phorbol 12, 13-dibutyrate and phosphatase inhibitors, okadaic acid and calyculin A increased the inward currents passing through the L-type VDCs. These effects were inhibited by protein kinase inhibitors, H-7 and staurosporine. The CCh effect was also inhibited by GDPβS. Therefore, it seems possible that DG, a product of phosphatidylinositol break-down might mediate muscarinic effects on L-type VDC, the last via stimulation of protein kinase C, and that L-type VDC activity might be modulated by protein kinase C-mediated phosphorylation and protein phosphatase type-1-mediated dephosphorylation of the channel or related protein(s) in guinea pig taenia coli smooth muscle cells.View full abstractDownload PDF (14076K) -
Yuji IMAIZUMI, Katsuhiko MURAKI, Satoshi HENMI, Minoru WATANABE1993 Volume 101 Issue 3 Pages 153-167
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThe major functional roles of K channels in smooth muscle cells are as follows: (i) Keeping resting membrane potential (RMP). (ii) Induction of hyperpolarization (HP) in response to bioactive substances. (iii) Facilitation of action potential repolarization (APR). (iv) Induction of action potential afterhyperpolarization (AH). (v) Facilitation of slow wave repolarization. (vi) Inhibition of depolarization and/or action potential. Major background K channels responsible for RMP have not been identified yet, whereas it is been postulated that several K channels including Ca-dependent K channels and ATP-dependent K channels may co-contribute in part to RMP. Further activation of these channels by bioactive substances results in hyperpolarization and muscle relaxation. APR and AH in several types of smooth muscles are due to activation of mainly large conductance Ca-dependent K channels (BK) and additionally delayed rectifier K channels. Moreover, another type of delayed rectifier K channels and early inactivating K channels may also contribute to some of the functional roles shown above. Although activation of Ca-dependent Cl channels in response to agonists depolarizes the cell membrane in several types of smooth muscle cells, a single channel current has not been identified. Ca-dependent K and Cl currents can be regulated by intracellular Ca store sites, which may be exhausted after a large release induced by inositol 1, 4, 5-trisphosphate or caffeine. The Ca-pump activity in the store sites may also regulate indirectly but strongly the activity of the channels and consequently membrane excitability.View full abstractDownload PDF (31703K) -
Kazunori YAMAMOTO, Hideki TAKASE, Ken-ichi ABE, Yuji SAITO, Akira SUZU ...1993 Volume 101 Issue 3 Pages 169-175
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSWe studied the effects of a preparation containing Berberine and Geranii Herba (BGH) on different diarrheal models of mice and the contractions of isolated guinea pig intestinal smooth muscle, comparing these effects with those of a preparation containing creosote (CSG) and loperamide (LP). BGH, as well as CSG and LP, significantly inhibited the diarrhea induced by castor oil or BaCl2, but not the diarrhea induced by pilocarpine or serotonin. BGH inhibited ACh-, Ba2+ or electrical stimulation (ES)-induced contraction of the ileum or colon at concentrations from 10-6 to 10-4 g/ml. On the other hand, the inhibitory effect of CSG on the ES-induced contraction was about one hundred times stronger than that on ACh or Ba2+-induced contraction. The order of the inhibitory potency of LP on contractions of the ileum in this test was ES > Ba2+ > ACh, and LP showed stronger inhibition against the contraction of the ileum than that of the colon. These results suggest that BGH exerts its antidiarrheal action by inhibiting intestinal movement, and the mechanism of action of BGH may differ from those of CSG or LP.View full abstractDownload PDF (13719K) -
Toshihiro MATSUMURA, Hiroyasu FURUICHI, Junkichi IZUMI, Yumiko KAMATSU ...1993 Volume 101 Issue 3 Pages 177-186
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThe anti-ischemic and anoxic effects of NC-1100, a piperazine type calcium channel blocker, were investigated in various cerebral ischemia and anoxia models in mice, gerbils and guinea pigs. Minimal effective doses of NC-1100 were 8 mg/kg, i.p. and 30 mg/kg, p.o. for KCN-induced anoxia; 16 mg/kg, i.p. for decapitation-induced gasping; 30 mg/kg, i.p. for cerebral ischemia induced by occlusion of bilateral carotid arteries in gerbils; and 10 μM for the in vitro ischemic model in hippocampal slices. Moreover, NC-1100 attenuated the disturbance of cerebral energy metabolism induced by decapitation in mice. These results suggest that NC-1100 has a cerebral protective effect, and that attributable to its ability to improve the cerebral energy metabolism disturbance.View full abstractDownload PDF (15586K) -
Mikio MASUDA, Hiroshi TAKEDA, Takeshi SHIBUYA1993 Volume 101 Issue 3 Pages 187-196
Published: 1993
Released on J-STAGE: February 06, 2007
JOURNAL FREE ACCESSThe difference of amine dynamics in central noradrenergic, dopaminergic and serotonergic systems of adaptive or non-adaptive rats to repeated restraint stress was investigated neurochemically. A single immobilization induced stress responses, such as reductions in growth rate, food intake, water intake and locomotor activity, and an increase in pain threshold. These responses disappeared after repeated immobilization 1 or 2 hr daily for 7 days, but not after 4 hr daily for 7 days. These results suggest that stress adaptation models should include the parameter of repeated exposure to restraint stress 1 or 2 hr daily for 7 days. In the frontal cortex, midbrain-thalamus, striatum, hypothalamus, medulla-pons, cerebellum, cervical cord, thoracic cord and lumbar cord of models with adaptability to repeated restraint stress, a marked increase in serotonin (5-HT) turnover was observed. This neurochemical change was seen in the hypothalamus and lumbar cord of non-adaptive models, but not in the other brain and spinal cord regions. Also, an increase in norepinephrine (NE) turnover in spinal cord regions was observed in adaptive models, but NE turnover was decreased in the frontal cortex, striatum or cervical cord of non-adaptive models. These findings suggest that enhancement of central 5-HT turnover and NE turnover in the spinal cord contribute to the formation of adaptation to repeated restraint stress.View full abstractDownload PDF (17364K)
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