Voltage‐dependence of ryanodine‐sensitive component of contraction in A23187‐ and isoprenaline‐treated cardiac muscles

Kondo, Noriaki

doi:10.1111/j.1476-5381.1989.tb16862.x

Cited by 4 publications

(1 citation statement)

References 31 publications

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“…A23187, a divalent cationic ionophore, has been shown to release nonimmunologically anaphylactic mediators from lung with subsequent smooth muscle contraction (Piper & Seale, 1979;Fleisch et al, 1982;Burka, 1983;Cheng et al, 1987). In addition, A23187 can directly activate smooth muscle contraction by increasing cytoplasmic free Ca2+ concentration via enhancement of transmembraneous Ca2+ influx and intracellular Ca2 + release (Kondo, 1989). The concentration-response curve for IgG-sensitized lung segment 1 to ovalbumin was to the left of those for the other lung segments.…”

Section: Discussionmentioning

confidence: 90%

Pharmacological and histological examinations of regional differences of guinea‐pig lung: a role of pleural surface smooth muscle in lung strip contraction

Wong

Bloomquist

Bendele

et al. 1992

British J Pharmacology

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1Parenchymal lung strip preparations have been widely used as an in vitro model of peripheral airway smooth muscle. The present study examined functional responses of 4 consecutive guinea-pig lung parenchymal strips isolated from the central region (segment 1) to the distal edge (segment 4) of the lower lung lobe. The middle two segments were designated as segments 2 and 3. 3 Contractile responses of segments 1 and 4 to antigen-challenge (ovalbumin), ionophore A23187 and substance P were significantly greater than the other 2 segments with respect to either sensitivity or maximum responsiveness.4 U46619-induced contractions of the 4 lung segments were relaxed in similar manner by papaverine and theophylline up to 100%, salbutamol up to 80%, and sodium nitroprusside by only 20%. In contrast, sodium nitroprusside markedly reversed U46619-induced contraction of pulmonary arterial rings and bronchial rings.5 Histological studies identified 2-4 layers of smooth muscle cells underlying the lung pleural surface. Mast cells were prominent in this area. Moreover, morphometric studies showed that segment 4 possessed the least amount of smooth muscle structures from bronchial/bronchiolar wall and vasculatures as compared to the other 3 segments, and a significant difference in this respect was evident between segment 1 and segment 4. 6 Since lung segments 1 and 4 are covered with larger surface area of lung pleura, the present results suggest that the significantly greater intrinsic contractile responses of segments 1 and 4 are associated with the presence of increased lung pleural surface possibly together with more mast cells. Thus, a primary contribution to the net contraction of the lung parenchymal strips may be smooth muscle from the lung pleura, alveolar ducts and interstitial contractile cells rather than from bronchi/bronchioles and microvasculatures.

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Section: Discussionmentioning

confidence: 90%

Pharmacological and histological examinations of regional differences of guinea‐pig lung: a role of pleural surface smooth muscle in lung strip contraction

Wong

Bloomquist

Bendele

et al. 1992

British J Pharmacology

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Deformation of the Bowditch staircase in Ca2+-overioaded mammalian cardiac tissue — a calcium phenomenon?

Löhn

Szymanski

Markwardt

1996

Biochemical Mechanisms in Heart Function

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Deformation of the Bowditch staircase in Ca2+-overloaded mammalian cardiac tissue ? a calcium phenomenon?

1996

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Concentrations of 1-4 mumol l-1 isoproterenol cause both in right ventricular papillary muscles and in enzymatically isolated myocytes of the guinea-pig a Ca2+ overload-induced state which is functionally characterized by biphasic (multiphasic) twitches and biphasic (multiphasic) intracellular calcium transients, respectively, during excitation-contraction coupling. This state was stabilized in the in vitro experiments for some hours by a co-ordination of the interstimulus interval, the temperature of the superfusion fluid and the addition of calcium agonists. The functional stability is the precondition for the reproducibility of the experimental results particularly after the application of long-lasting stimulation programmes. Changes in the shape of biphasic contractions were compared with changes in the time course of biphasic intracellular calcium transients using three manipulations of a different kind: (1) the interruption of the steady pacing rhythm, (2) the variation of the interstimulus interval, (3) the addition of ryanodine. It was shown that: (1) The BOWDITCH staircase in calcium overloaded multicellular preparations is changed in that each individual component of the twitch passes through its own staircase. A homologous behaviour can be observed in the configuration of the phasic and tonic component of biphasic intracellular calcium transients. (2) At different driving frequencies the relative proportion of the two components of a biphasic twitch corresponds to the time integrals of the two components of biphasic intracellular calcium transients. (3) Ryanodine suppresses both the first component of the biphasic twitch and the phasic component of the biphasic intracellular calcium transient. The SR Ca(2+)-ATPase inhibitor thapsigargin increases the second component of the biphasic calcium transient. This supports the hypothesis that the size of the tonic component is in part determined by intracellular calcium reuptake. The results of both kinds of experiments would be compatible with the assumption that in calcium overloaded mammalian cardiac cells calcium reaches the contractile system directly as well as via two intracellular stores ('extended two-Ca-store concept').

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Voltage‐dependence of ryanodine‐sensitive component of contraction in A23187‐ and isoprenaline‐treated cardiac muscles

Cited by 4 publications

References 31 publications

Pharmacological and histological examinations of regional differences of guinea‐pig lung: a role of pleural surface smooth muscle in lung strip contraction

Pharmacological and histological examinations of regional differences of guinea‐pig lung: a role of pleural surface smooth muscle in lung strip contraction

Deformation of the Bowditch staircase in Ca2+-overioaded mammalian cardiac tissue — a calcium phenomenon?

Deformation of the Bowditch staircase in Ca2+-overloaded mammalian cardiac tissue ? a calcium phenomenon?

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