Biomedical subjects

N G Kochemasova

Publications and source records attributed to N G Kochemasova.

At least 19 recordsLinked to original sources

PubMed1982

[Excitation-contraction coupling in the smooth muscle cells of the portal vein as affected by noradrenaline].

Verapamil (10(-5) M) blocked phasic and tonic components of potassium contracture of smooth muscle cells (SMC) of the rat portal vein but failed to block completely noradrenaline, induced contraction of these cells, neither did it suppress the NA-induced contraction of the portal vein SMC in the presence of potassium contracture. These data suggest that NA-induced contraction is activated by external Ca2+ ions entering the SMC through chemosensitive (NA) voltage-independent Ca channels of the membrane. The contraction blocked by verapamil is activated by external Ca2+ ions entering through fast voltage-dependent inactivating Ca channels participating in AP generation, and slow voltage-dependent inactivating Ca channels opened by NA depolarization. The basal tone and contraction evoked by transmitters and physiologically active substances in the SMC of all blood vessels seem to be activated primarily by external Ca2+ entering the SMC via the above mentioned types of Ca channels.

Action Potentials↗

PubMed1982

[Mechanism of modulating effect of histamine on the excitation and contraction of smooth muscles of the ureter].

Experiments were carried out on smooth muscle cells (SMC) of the guinea-pig ureter by the double sucrose gap method with simultaneous recording of electrical and contractile activities. The effect of histamine on SMC was studied in normal Krebs solution and in sodium-free Krebs solution with TEA. In normal Krebs solution, histamine was shown to increase the duration of AP plateau and contraction. In sodium-free Krebs solution with TEA, the APs of ureter SMC also had a plateau that was determined by the increased calcium conduction of the membrane. In these conditions, histamine provoked a decrease in the duration of the AP plateau and contraction. The histamine effect was blocked by phencarol both in normal and sodium-free Krebs solution with TEA. A possible role of sodium, calcium and potassium ions in the modulating action of histamine on excitation of ureter SMC is discussed.

Action Potentials↗

PubMed1981

[Mechanism of the relaxant action of noradrenaline on coronary artery smooth muscle cells].

Electrical and contractile activity of smooth muscle cells (SMC) of bovine coronary arteries was examined by the double sucrose gap method. It was shown that, on the one hand, noradrenaline increased the potassium membrane permeability followed by hyperpolarization which led to the closing of potential-dependent show calcium channels and to the reduction of the transmembrane calcium ion influx. On the other hand, noradrenaline closed potential-dependent chemosensitive calcium channels that limited influx of extracellular calcium ions into SMC. Such a double-noradrenaline effect resulted in a considerable decrease of the concentration of intracellular calcium ions and in the falling of the basal tone of arterial SMC.

Animals↗

PubMed1980

[Effect of potassium ions on electrogenesis and contraction of ureter smooth muscle].

In the ureter smooth muscle cells, high--K solution produced a depolarization at the onset of which the action potentials (AP) and contraction occur; the latter consists of an initial phasic (Ph) and subsequent tonic (T) components. Ph component is initiated by the AP, T component--by a stable potassium depolarization. In Ca--free solution the AP, Ph and T components are blocked, although a sustained potassium depolarization is preserved. Basing on these results it is suggested that: 1) phasic contraction is initiated by calcium ions influxed via fast potential--dependent calcium channels participating in the AP generation; 2) tonic contraction is also initiated mainly by extracellular calcium influx through slow potential--dependent calcium channels of plasmatic membrane that appear to be similar to calcium channels of sarcoplasmic reticulum membrane in skeletal muscles and of the membrane of presinaptic nerve terminals.

Action Potentials↗

PubMed1980

[Effect of manganese ions and verapamil on electrogenesis and contraction of ureter smooth muscle].

Fast and slow calcium channels of the electrically excitable membrane of the ureter smooth muscle cells had different sensitivity to manganese ions and verapamil. Manganese ions (10(-4) M) selectively blocked the fast potential--dependent Ca--channels, Ca ions being necessary for phasic contraction, whereas verapamil (10(-9)--10(-8)) specifically blocked the slow potential--dependent CA--channels.

Action Potentials↗

PubMed1980

[Mechanisms of activation of coronary vessel smooth muscle contraction].

Experiments have been performed with smooth muscle cells (SMC) of the circular strips from the bovine left descending anterior heart artery with a diameter of 2--2.5 mm. Use was made of the double sucrose gap method with simultaneous recording of electric and contractile activity of SMC. The cathode of polarizing current produced depolarization of SMC membrane (cathelectrotone). After depolarization of the membrane reached the threshold, the action potential (AP) was generated, followed by SMC contraction. The anode of polarizing current caused hyperpolarization of the membrane (anelectrotone) accompanied by relaxation of the strip. The degree of relaxation depended upon the initial muscle tone and the magnitude of anelectrotonic hyperpolarization. The voltage-current characteristics of SMC show that the muscle cell membrane of the coronary arteries possesses pronounced rectifying properties. An increase in the external potassium concentration up to 160 mM results in depolarization of the SMC membrane preceded by AP. These changes are accompanied by initial phasic and subsequent tonic contraction. The phasic component of the contraction is suggested to be evoked by AP and tonic component by stable potassium depolarization.

Action Potentials↗

PubMed1978

[Selective inhibition of the tonic component of portal vein smooth muscle cell potassium contracture by verapamil].

The studies were performed on the rat portal vein smooth muscle cells, using double sucrose-gap method. 10(-9)--10(-7) M-verapamil was shown to selectively block the tonic component of potassium contracture. Since potassium depolarization of the membrane persists, it may evidence that verapramil had a specific effect on the excitation-contraction coupling by blocking the passive calcium entry into the muscle cells. At higher concentrations (10(-6)--10(-5) M) verapramil produced inhibition of the phasic component of potassium contracture by blocking the potential-dependent calcium canals of the portal vein smooth muscle cell membrane responsible for generation of the action potentials.

Action Potentials↗

PubMed1977

[Effect of increased calcium ion concentration on the electrical and contractile activity of guinea pig ureter smooth muscle].

Experiments were performed on the smooth muscle cells of the guinea pig ureter by means of the double sucrose-gap method. An increase of Ca2+ concentration (22 mM/1) in Ringer-Locke solution causes hyperpolarization and a slight increase of the membrane resistance. The amplitude of the first spike potential and the plateau decreases, the amplitude of oscillations increases. In sodium-free Ringer-Locke solution when the action potential in the smooth muscle cells of the ureter turns into a simple spike potential, an increase of Ca2+ concentration causes a marked increase of the action potential amplitude.

Action Potentials↗

PubMed1976

[Synaptic potentials in smooth muscle cells].

Investigations were carried out on smooth muscle cells (SMC) of rat and rabbit anococcygeus by the method of a double "sugar bridge" in the presence of tetraethylammonium (1 mM/1) in the Krebs solution. Stimulation of the muscle strip by the electric current rectangular pulse of the maximal value and of short duration caused the development of excitatory postsynaptic potentials (EP SP) in the rat and rabbit SMC, and of inhibitory postsynaptic potentials in the rabbit SMC. The value of postsynaptic potentials displayed a linear dependence on the level of the membrane potential. Elimination of chlorine ions from the external solution decreased the EP SP of the SMC of rabbit anococcygeus and shifted the reversion potential in the direction of sodium balance potential. Apparently generation of the EP SP of the SMC of rabbit anococcygeus was associated with the increased permeability of the membrane both for sodium and for chlorine ions.

Action Potentials↗

PubMed1972