The membrane properties of the smooth muscle cells of the rabbit main pulmonary artery.
TLDR
During outward current pulses, the membrane shows marked rectification and action potentials can never be generated, so this smooth muscle tissue is classified as a single‐unit type.Abstract:
1 The membrane potential of the smooth muscle cells of the rabbit main pulmonary artery amounts to -57 mV, the length constant of the tissue is 148 mm and the time constant of the membrane 182 msec On the basis of the electrical properties of its membrane, this smooth muscle tissue is classified as a single-unit type During outward current pulses, the membrane shows marked rectification and action potentials can never be generated2 Tetraethylammonium (10 mM) and procaine (5 mM) depolarize the membrane and increase the membrane resistance By studying the effect of both substances on the (42)K efflux, it could be concluded that they reduce the K-permeability of the membrane They also suppress the rectification of the membrane and increase the length constant of the membrane In the presence of TEA and procaine, a graded response of the membrane can be induced by outward current pulses, but overshoot potentials never occur3 Noradrenaline, in concentrations between 2 x 10(-8) and 10(-7)M, evokes contraction without depolarizing the membrane When the concentration is increased above 2 x 10(-7)M, noradrenaline depolarizes the membrane and reduces the membrane resistance A study of the effect of noradrenaline on the K, Cl and Na fluxes has revealed that it increases the permeability of the membrane for these three ions4 The tissue concentrations of Na and K are 80 and 38 m-mole/kg wet wt, respectively The amount of Cl in the cellular compartment was measured by an extrapolation procedure and found to be 13 m-mole/kg wet wt The extracellular space measured with [(14)C]sorbitol is 550 ml/kg wet wt and the dry wt/wet wt ratio 19% The calculated equilibrium potentials for K, Na and Cl (E(K), E(Na) and E(Cl)) are -83, +59 and -26 mV, respectively In efflux experiments under steady-state conditions, the following rate constants have been calculated: 0092 min(-1) for Na, 0029 min(-1) for Cl and 00054 min(-1) for K The calculated value for the ratio P(Na)/P(K) was 022 and for P(Cl)/P(K) 0635 K-free solution and 2 x 10(-6)M ouabain depolarize the cells by about 8 mV After exposure of the cells to K-free solution, they hyperpolarize on readmission of K, suggesting that part of the membrane potential could be due to electrogenic transport of ions6 A decrease of external Ca depolarizes the cells and increases the membrane resistance Na-deficiency hyperpolarizes these smooth muscle cells but this procedure does not prevent the depolarization induced by Ca deficiencyread more
Citations
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Hypoxic pulmonary vasoconstriction.
TL;DR: Evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension is evaluated.
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Direct role for potassium channel inhibition in hypoxic pulmonary vasoconstriction.
TL;DR: Results indicate that K+ channel inhibition may be a key event that links hypoxia to pulmonary vasoconstriction by causing membrane depolarization and subsequent Ca2+ entry.
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Exchange characteristics of the noradrenaline-sensitive calcium store in vascular smooth muscle cells or rabbit ear artery.
Rik Casteels,Guillaume Droogmans +1 more
TL;DR: The results suggest that the filling of the store under physiological conditions occurs by a direct pathway between the store and the extracellular medium.
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Physiological Features of Visceral Smooth Muscle Cells, With Special Reference to Receptors and Ion Channels
TL;DR: The features of ion channels in vascular tissues only recently are reviewed, since this article makes only limited reference to vascular smooth muscle research.
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Electromechanical and pharmacomechanical coupling in vascular smooth muscle
Avril V. Somlyo,Andrew P. Somlyo +1 more
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TL;DR: The cable properties of smooth muscle of guinea‐pig taenia coli were studied by intracellular recording of electrotonic potentials produced by square current pulses and alternating current applied with external electrodes.
Journal Article
Differential effect of verapamil on excitation-contraction coupling in smooth muscle and on excitation-secretion coupling in adrenergic nerve terminals.
TL;DR: In a nonvascular type of smooth muscle, verapamil reduced the contractions caused by Ca++ in depolarized and by norepinephrine in the polarized preparation, compatible with the view that the spasmolytic effect of verAPamil in smooth muscle is due to a selective Ca++-antagonistic effect of the drug.
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Excitation and contraction in bovine tracheal smooth muscle.
TL;DR: Acetylcholine, and to a smaller extent histamine, are less dependent upon the presence of extracellular calcium, and may be capable of releasing calcium sequestered within the cell; acetyl choline appears to be more effective in releasing sequestered calcium.
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