Muscle Of Guinea-pig Taenia Coli Research Articles

The relative contribution of K and Cl to the total increase of membrane conductance produced by adrenaline on the smooth muscle of guinea-pig Taenia coli.

1. The relative contribution of K and Cl to the total increase of membrane conductance produced by adrenaline on the smooth muscle of guinea-pig taenia coli has been investigated. Constant current pulses were applied with a pair of large external electrodes, the voltage change was recorded with an intracellular micro-electrode, and the change in the size of the electrotonic potential by adrenaline was measured.2. Adrenaline hyperpolarized the membrane by about 8 mV with a range from 5 to 15 mV and it reduced both the size and the time course of the electrotonic potential. On the average the size was reduced to 65 +/- 1.8% (n = 75) of the normal size, from which a decrease of the membrane resistance to 45 +/- 2.2% was calculated, or 48% allowing for the spatial decay.3. The magnitude of the reduction of the electrotonic potential caused by adrenaline was decreased as the concentration of K or Cl ions in the medium was reduced by substituting NaCl or sucrose for KCl or an impermeant anion, benzene sulphonate, for Cl ions. The adrenaline effect remained unaltered when the NaCl was replaced with Tris-Cl.4. It is therefore concluded that adrenaline opens the ion pathways mainly for K and Cl.5. On the basis of the changes in potential and in conductance caused by adrenaline, the equilibrium potential for its action was calculated as - 75 mV.6. The ratio of the Cl component to the K component of the additional conductance increase was obtained as 0.36 using the calculated equilibrium potential and the Nernst potentials for K (-91 mV) and Cl (-31 mV).

Ca flux and action potential in smooth muscle of guinea-pig taenia coli.

Ca flux and action potential in smooth muscle of guinea-pig taenia coli.

Interaction of 28Mg with Ca and K in the smooth muscle of guinea-pig taenia coli.

1. The uptake of (28)Mg, and the total tissue content of Mg, Ca, Na and K have been determined in the smooth muscle of the guinea-pig taenia coli. The Mg content was 6.56 m-mole/kg fresh wt. immediately after dissection, falling slowly to 5.11 after 6 hr immersion in Krebs solution at 37 degrees C.2. The Mg content rose to 15.4 m-mole/kg fresh wt. during immersion in isotonic sucrose containing only MgCl(2). It was independent of the Mg(2+) concentration in this solution, but was depressed when K(+) or Ca(2+) ions were added.3. (28)Mg uptake showed three separate phases, extracellular, intermediate and slow. The size of the extracellular phase was proportional to the Mg(2+) concentration in the solution, but the size of the slow phase was constant. The size of the intermediate phase, exchanging with a half-time of a few minutes, was depressed when K(+) or Ca(2+) ions were added.4. The results are compatible with a competition between Mg in the intermediate phase of tracer exchange, and K(+) or Ca(2+) ions for fixed anionic sites in the tissue.

Increase of membrane conductance by adrenaline in the smooth muscle of guinea-pig taenia coli.

(1) The double sucrose-gap method was used to record changes in membrane resistance in intestinal smooth muscle strips. (2) Adrenaline reduced the membrane resistance; it hyperpolarized the membrane and blocked spontaneous and evoked spikes. (3) When the membrane potential was shifted by applying conditioning current, the hyperpolarization produced by adrenaline was larger during depolarization and smaller during hyperpolarization. The hyperpolarization caused by adrenaline was converted into depolarization by 18 to 20 mV conditioning hyperpolarization. (4) The resting membrane resistance was increased in the absence of potassium and in low external chloride (replaced with benzene- or ethane-sulphonate); it was decreased by excess potassium and by nitrate substitution for chloride. (5) The reduction of the membrane resistance by adrenaline was potentiated by high external potassium and by replacement of chloride with nitrate; it was diminished by low external potassium and by replacement of chloride with benzene- or ethane-sulphonate. (6) The hyperpolarization by adrenaline was reduced by raising the external potassium concentration; it was increased by lowering the external potassium concentration. In a solution containing low chloride and high potassium (24 m M ), adrenaline often produced depolarization. (7) It was concluded that adrenaline increases mainly the potassium conductance and also the chloride conductance of the smooth muscle cell membrane. Sodium seemed to be less important for the adrenaline action.

The effect of sodium and calcium on the action potential of the smooth muscle of the guinea-pig taenia coli.

1. Spontaneous spike activity and action potentials evoked by external field stimulation were recorded, intracellularly and with the double sucrose gap method, from the smooth muscle of guinea-pig taenia coli.2. Replacement of external NaCl with sucrose (leaving 10 mM-Na in the buffer) caused hyperpolarization and stopped spontaneous activity within 10 min. Spikes could, however, be evoked for 2-3 hr. The amplitude, the overshoot and rate of rise of the spike were increased.3. In 10 mM-[Na](o) the intracellular Na concentration was reduced from 35 to 24 mM, shifting the Na-equilibrium potential from +34 to -22 mV.4. Excess Ca (12.5 mM) caused hyperpolarization and increased membrane conductance. The amplitude and the rate of rise of the spike were increased, the threshold was raised and the latency of the spike evoked by threshold stimulation became shorter.5. The effect of reducing the external Ca concentration depended on the Na concentration present, being greater with higher external [Na](o). When the membrane was depolarized and spikes deteriorated in low Ca (0.2-0.5 mM) reduction of Na to 10 mM caused repolarization and recovery of the action potential.6. Mn (0.5-1.0 mM) blocked spontaneous spike discharge after 20 min. Higher concentrations (more than 2.0 mM) were required to block the evoked action potential.7. The results indicate that the smooth muscle spike in taenia is due to Ca-entry and that Na influences spike activity indirectly by competing with Ca in controlling the membrane potential.

The effect of temperature on the membrane conductance of the smooth muscle of the guinea-pig taenia coli.

1. The effect of temperature on the membrane conductance of the smooth muscle of guinea-pig taenia coli was investigated electrophysiologically, using the double sucrose gap method, and by ion-flux determinations.2. In the range between 19 degrees C and 37 degrees C, the membrane conductance increased with rising temperature and decreased with cooling (Mean Q(10) about 2.5).3. When the Cl concentration in the external medium was low (Cl(-) substitution with benzene-sulphonate), the effect of changing the temperature was smaller (Mean Q(10) about 1.5).4. In muscle depolarized by excess K (27 mM) in a solution containing low Cl, cooling repolarized the membrane and markedly increased membrane resistance.5. The slow phases of the (42)K- and (36)Cl-exchange were greatly slowed by cooling which did not change the rate constants of the (24)Na-efflux curve. Thus observations on the rate of exchange of ions agreed with the electrophysiological findings indicating a reduction of K- and Cl-conductance of the cell membrane at low temperature.6. The depolarization produced by lowering the external Ca-concentration was greatest at high temperature (37 degrees C). With cooling the membrane was repolarized and membrane resistance increased.7. The sustained state of depolarization observed when the external Ca was replaced by Ba (2.5 mM) at high temperature (37 degrees C) was terminated by cooling.8. The observations may be interpreted by the hypothesis that Ca, located at two different membrane sites, controls, independently, at the outer layer mainly Na- (and Ba-) permeability and at the inner layer mainly K-permeability, the Ca-binding at these sites being affected by temperature in the opposite direction.

The effects of divalent cations on the glycerinated smooth muscle of guinea-pig taenia coli.

Using glycerinated taenia coli of the guinea-pig, the effects of divalent ions (Ca, Mg, Mn and Zn) on the contractile system of the smooth muscle were studied. Mg ion is essential for ATP contraction of glycerinated smooth muscle. Mn ion can substitute perfectly for Mg ion, but Ca ion cannot. The initiation of ATP-contraction in the presence of Mn ion is suppressed by addition of higher concentra-tion of Ca ion. Zn depresses the initiation of ATP-contraction, but it is ineffective in relaxing the ATP-contraction. The present results imply that Zn ion depresses the initiation of contraction by blocking all stages of contractile process in the smooth muscle.

Effects of Mn and Zn ions on the contraction of smooth muscle of guinea-pig Taenia coli.

The effects of Nn, Zn and Mg ions on the contraction of smooth muscle of taenia coli from guinea-pig were studied. Both Mn and Zn ions suppress both spontaneous and electrically induced contractions. The suppressing effect of Mn ion appears promptly and is reversible, while the effect of Zn appears slowly and is irreversible. These results suggest that Mn ion acts on the excitation process in the memb-rane and Zn ion acts not only on excitation in the membrane, but also directly on the contractile system. Ca ion competes with Mn and Zn ions in the suppression of both spontaneous and electrically induced contractions. However, the competition of Ca ion with Zn ion is effective only when Ca is present prior to the addition of Zn ion.

Effects of Mn, Zn and Mg ions on the electrical activities of smooth muscle of guinea-pig taenia coli.

The effects of Nn, Zn and Mg ions on the membrane potential and contraction of the smooth muscle from the guinea-pig taenia coli were investigated. The simultaneous recording of electrical and mechanical activities was performed using the sucrose-gap method and a mechano-electric transducer. Mn ions depressed spontaneous spike discharge without changing the membrane potential, and also perfectly depressed the spontaneous contraction. These effects of Mn ions were reversible. Mn ions competed with Ca ions in the spike discharge and contraction. The effects of Zn ions on the spontaneous spike discharge and contraction were similar to those of Mn ions, but they were irrever-sible. Mg ions at a high concentration depressed the spontaneous spike discharge, but did not influence the membrane potential. Reduction or lack of Mg ions induced an increase of spontaneous spike discharge. In media of high Mn or Zn, electrical stimulation was effective in eliciting the spike potential but failed to induce tension development. Such a dissociation between electrical and mechanical activities was also confirmed by KCl- and ACh-depolarization in media of high Mn or Zn. KCl-depolarizations without tension development were observed in high Mn and Zn media. ACh-depolarization without tension development was observed in high Mn media, but neither depolarization nor tension development was observed in high Zn media. Mg did not exert a suppressive effect on the KCl- or ACh-depolarization and contracture.

Ionic permeability of the guinea pig taenia coli muscle.

WITHIN less than 2 yr, two diametrically conflicting views of the ionic permeability of the guinea-pig taenia coli muscle have been published in Nature1,2. The first1 assumed by analogy with frog skeletal muscle3–5 that the membrane is permeable to Cl. The intracellular Cl was then calculated from Donnan considerations and the values so obtained seemed to agree quite well with estimates based on electrophysiological measurements of inhibitory postsynaptic potentials. The second report2 does not refer to the first, but it confirms still earlier data6 on the “anomalous” osmotic behaviour of taenia coli muscles. The muscles do not gain weight on prolonged exposure to isosmotic KCl-enriched media. They lose weight when exposed to media that are made hyperosmotic by addition of KCl.

Cable properties of smooth muscle.

1. 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.2. An electrical model of the smooth muscle was constructed to test how the junctional resistance between cells affected the cable properties. The model consisted of a series of short cables (representing cells) which were connected by junctional resistances.3. It was concluded, from the experiments on the living tissue and on the model, that the electrotonic potential in smooth muscle can be expressed by the ordinary cable equation used for nerve and skeletal muscle fibres, even though the junctional resistance is of the same order of magnitude as that of the myoplasmic resistance.4. The cable equation was used to analyse the membrane parameters from the electrotonic potential, from the time course of the foot of the spike and from the conduction velocity. The analysis indicates that the smooth muscle has a membrane capacity of 2-3 muF/cm(2) and a membrane resistance of 30-50 kOmega cm(2).

The effect of hypo- and hypertonic solutions on volume and ion distribution of smooth muscle of guinea-pig taenia coli.

1. The intra- and extracellular spaces and ionic content of the taenia coli of the guinea-pig have been measured in a series of bathing solutions in which the tonicity varied from 0.5 to 3 times the tonicity of the normal Krebs solution.2. Equilibrium of the tissue in the experimental solution is reached within about 30 min.3. The absolute values of the parameters measured have been shown to depend on the blotting technique used. These differences were eliminated by expressing the results as a percentage of the values found in the normal Krebs solution.4. In hypertonic solutions the cell behaves as a perfect osmometer, the cell volume changing in proportion to the tonicity of the bathing medium. Only a small amount of cations is lost from the cells. A considerable amount of chloride is lost, making the postulation of its replacement by some other anions necessary in order to maintain electroneutrality of the intracellular solution.5. In hypotonic solutions the cells do not behave as predicted for a perfect osmometer. In 0.5 hypotonic solution an actual decrease in cell volume was observed associated with an increase of the extracellular space probably due to penetration of [(14)C]sorbitol into the cell. The intracellular ionic concentration was decreased. These findings suggest damage of the cell membrane.6. The observed hyperpolarization of the membrane in hypertonic solution can be explained by the increased intracellular potassium concentration.

The effect of adrenaline on the adenosine otriphosphate and creatine phosphate content of intestinal smooth muscle

1. The smooth muscle of guinea-pig taenia coli was used to investigate the relation between metabolic and physiological effects of adrenaline. Electrical and mechanical activity was recorded with the sucrose gap technique and, in parallel experiments, the concentration of energy-rich phosphate compounds, adenosinetriphosphate and creatine phosphate, (ATP and CP) in the tissue was determined.2. Adrenaline (in concentrations from 2 x 10(-9) g/ml. to 5 x 10(-8) g/ml.) increased the tissue content of energy-rich phosphate compounds. This effect was coincident with the physiological, inhibitory effect on electrical and mechanical activity.3. After anaerobic exposure of the tissue to substrate-free medium, the biochemical and the physiological effects of adrenaline were both abolished; both recovered after readmission of oxygen and/or substrate.4. In muscles depleted of glycogen in substrate-free medium, either by anoxia or by high temperature, adrenaline produced its stabilizing effect on the cell membrane and the increase in ATP and CP content when beta-hydroxybutyrate was the substrate, i.e. in the complete absence of carbohydrate from the medium and from the tissue.5. When adrenaline was applied simultaneously with the readmission of substrate, the ATP and CP content of pieces treated with adrenaline was greater than of control pieces, though the tension of both was zero. This indicates that the effect was not secondary to the muscle relaxation but was the result of increased ATP synthesis.6. The physiological and biochemical effects of adrenaline were both abolished by the same concentration of imidazole (0.05 M).7. Low concentrations of ATP (1 x 10(6)-5 x 10(-6)M)-like adrenaline-inhibited electrical and mechanical activity of the taenia. This effect was also abolished by imidazole.

Response to insulin by guinea-pig taenia coli.

THE stimulating action of insulin on the metabolism of heart and striated muscle is well known, but the extent of its influence on smooth muscle is less clear and is variously assessed1–8. Preparations so far studied—such as aortic muscle5—7 and intestinal segments4—suffer from the disadvantage that they are damaged during preparation or, like uterine muscle1–3, have a highly individual endocrine response. Because of its ease of dissection and less specialized function, guinea-pig taenia coli muscle seemed an obvious tissue preparation with which to investigate the possible in vitro effects of insulin.

Model of the membrane of smooth muscle cells of the guinea-pig taenia coli muscle during transmission from inhibitory and excitatory nerves.

Model of the Membrane of Smooth Muscle Cells of the Guinea-Pig Taenia Cole Muscle During Transmission from Inhibitory and Excitatory Nerves

CALCIUM MOVEMENT IN THE SMOOTH MUSCLE OF GUINEA-PIG TAENIA COLI.

The movement of calcium ions in the smooth muscle of guinea-pig taenia coli under various conditions was estimated by means of radioisotope technique. Uptake of 45Ca was not affected by the temperature of the soaking Krebs solution, whereas the rate of efflux of 45Ca decreased considerably in low temperature Krebs solution. Ethylenediamine-tetraacetate (EDTA) increased not only the rate of loss of 45Ca but also influenced markedly the movements of sodium and potassium ions in this tissue; after 30 minutes' incubation in 4mM EDTA-Krebs solution, taenia coli lost about 60m-mole/kg wet wt. potassium and gained 55m-mole/kg wet wt. sodium. Depolarization by high potassium, application of adrenaline, histamine or scrotonin increased the efflux of calcium, but the effect of acetyl-choline was variable dependent on the state of muscle preparation.

THE EFFECTS OF TEMPERATURE AND SOME DRUGS ON THE IONIC MOVEMENTS IN THE SMOOTH MUSCLE OF GUINEA-PIG TAENIA COLI.

Sodium and potassium movements in smooth muscle of guinea-pig taenia coli were measured with radioactive isotopes. In low temperature (20°C and 2°C), uptake of 42K and loss of 24Na were reduced considerably, but loss of 42K and uptake of 24Na were not so much affected. Adrenaline (1×10-5g/ml) had no significant effect upon the movement of 24Na, though it had suppressed the spontaneous contraction completely. Acetylcholine, adrenaline, histamine and serotonin also increased the efflux of 42K.