RESUMEN
The effect of the haloperidol (HP), a dopamine D2-receptor antagonist on the function of ionic channels of the electrically excitable plasma membrane and on the cytoskeleton of Chara corallina cells was investigated. Haloperidol was shown to block plasmalemmal Ca2+ channels. Apart from Ca2+ current reduction, the presence of HP slowed the kinetics of both activation and inactivation of ionic channels. The influence of haloperidol on the membrane structure was reversible. After removal of the neuromodulator, both the amplitude and the kinetics of the current development were seen to be completely restored. HP had no effect on Ca2+-activated chloride channels. Haloperidol inhibited cytoplasmic motion related to microfilamentary complex. Once haloperidol was removed from cell washing solution, cytoplasmic motion was restored. These results let us to assume that in the presence of HP the concentration of free Ca2+ in cytoplasm increases. Also it can be assumed that plasmalemmal Ca2+-channels of Ch. corallina cells contain binding sites similar to dopamine receptors and their antagonists.
Asunto(s)
Antagonistas de Dopamina/farmacología , Haloperidol/farmacología , Transporte Iónico/efectos de los fármacos , Calcio , Membrana Celular , Chara , CitoplasmaAsunto(s)
Chara/metabolismo , Citotoxinas , Lactalbúmina , Ácido Oléico , Animales , Bovinos , Línea Celular Tumoral , Chara/citología , Chara/crecimiento & desarrollo , Citotoxinas/química , Citotoxinas/farmacología , Humanos , Canales Iónicos/metabolismo , Transporte Iónico/efectos de los fármacos , Lactalbúmina/química , Lactalbúmina/farmacología , Ácido Oléico/química , Ácido Oléico/farmacología , Proteínas de Plantas/metabolismoRESUMEN
The effect of the neurotoxin melittin on the activation of ion channels of excitable membrane, the plasmalemma of Characeae algae cells, isolated membrane patches of neurons of mollusc L. stagnalis and Vero cells was studied by the method of intracellular perfusion and the patch-clamp technique in inside-out configuration. It was shown that melittin disturbs the conductivity of plasmalemma and modifieds Ca(2+)-channels of plant membrane. The leakage current that appears by the action of melittin can be restored by substituting calmodulin for melittin. Melittin modifies K(+)-channels of animal cell membrane by disrupting the phospholipid matrix and forms conductive structures in the membrane by interacting with channel proteins, which is evidenced by the appearance of additional ion channels.
Asunto(s)
Canales de Calcio/efectos de los fármacos , Membrana Celular/efectos de los fármacos , Meliteno/farmacología , Canales de Potasio/efectos de los fármacos , Animales , Chlorocebus aethiops , Potenciales de la Membrana/efectos de los fármacos , Moluscos/citología , Neuronas/efectos de los fármacos , Nitella/citología , Técnicas de Placa-Clamp , Células VeroAsunto(s)
Calcio/farmacología , Células Madre Embrionarias/citología , Células Madre Embrionarias/efectos de los fármacos , Animales , Calcio/metabolismo , Permeabilidad de la Membrana Celular/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Medios de Cultivo , Células Madre Embrionarias/metabolismo , Ratones , Células Madre Pluripotentes/citología , Células Madre Pluripotentes/efectos de los fármacos , Células Madre Pluripotentes/metabolismoRESUMEN
Ionic currents in the plasmalemma of perfused Nitella syncarpa cells identified as currents through Ca2+ channels were registered for the first time. The effect of 1,4-dihydropyridine derivatives (nifedipine, nitrendipine, riodipine) and phenylalkylamines (verapamil, D600) as well as the agonist CGP-28392 on the Ca2+ channels in the plasmalemma of perfused cells of Nitellopsis obtusa and Nitella syncarpa have been studied. A blocking effect of 1,4-dihydropyridine derivatives and phenylalkylamines on the plasmalemma Ca2+ channels has been detected. Phenylalkylamines have been found to block both inward and outward Ca2+ currents. The activating effect of the agonist CGP-28392 on the Ca2+ channels of plasmalemma has been shown.
Asunto(s)
Bloqueadores de los Canales de Calcio/farmacología , Canales de Calcio/efectos de los fármacos , Chlorophyta/efectos de los fármacos , Agonistas de los Canales de Calcio/farmacología , Canales de Calcio/fisiología , Membrana Celular/efectos de los fármacos , Dihidropiridinas/farmacología , Potenciales de la Membrana , Nifedipino/farmacología , Nitrendipino/farmacología , Perfusión , Piridinas/farmacologíaRESUMEN
Ca2+ current recordings have been made on Nitella syncarpa cells using the intracellular perfusion and the voltage-clamp technique. TPA (12-O-tetradecanoylphorbol-13-acetate), a substance capable of activating protein kinase C from plasmalemma of Nitella cells, modulates voltage-dependent Ca2+ channels. Polymixin B, inhibitor of protein kinase C, blocks the Nitella plasmalemma Ca2+ channels; the rate of channel blockage depends on the concentration and exposure time of the substance.
Asunto(s)
Canales de Calcio/fisiología , Fenómenos Fisiológicos de las Plantas , Proteína Quinasa C/fisiología , Calcio/fisiología , Membrana Celular/fisiología , Conductividad Eléctrica , Potenciales de la Membrana , Polimixina B/farmacología , Acetato de Tetradecanoilforbol/farmacologíaRESUMEN
Effects of local anesthetics (LA) and a number of organic cations on Ca2+-activated Cl-channels in plasmalemma of intracellularly perfused giant algae Nitellopsis obtusa were studied using voltage-clamp technique. It was shown earlier that Ca2+ ions cause irreversible inactivation of Cl-channels with a characteristic time equal to a few minutes, but not only activate Cl-channels. It has been found that amphiphilic cations (AC), including LA+, introduced intracellularly together with Ca2+ produced delayed action on the beginning of the inactivation process (approximately ten minutes) producing no effect on activation during this period. The time of delayed action was linearly dependent on the concentrations ratio alpha = [AC]/[Ca2+]. Procaine is the most effective agent in this respect, the time of its delayed action on the inactivation process being 20 min at alpha = 1. LA in the neural form, hydrophilic AC of tetraethylammonium, as well as LA+ from the outside had no effect on Cl-channels. Cl-channels inactivated "irreversibly" by Ca2+ ions may be restored after addition of AC in Ca2+-containing perfusion medium.
Asunto(s)
Anestésicos Locales/farmacología , Calcio/farmacología , Cloruros/metabolismo , Eucariontes/efectos de los fármacos , Canales Iónicos/efectos de los fármacos , Proteínas de la Membrana/metabolismo , Cationes/farmacología , Canales de Cloruro , Canales Iónicos/metabolismo , Procaína/farmacologíaRESUMEN
Experiments were carried out on the algal cells with removed tonoplast using both continuous intracellular perfusion and voltage clamp on plasmalemma. The transient plasmalemma current induced by depolarization disappeared upon perfusion with the Ca2+-chelating agent, EGTA, since the voltage-dependent calcium channels lost their ability to activate. Subsequent replacement of the perfusion medium containing EGTA by another with Ca2+ for clamped plasmalemma (-100 mV) induced an inward C1- current which showed both activation and inactivation. The maximal amplitude of the current at [C1-]in = 15 mmol/l (which is similar to that in native cells) was approximately twice that in electrically excited cell in vivo. The inactivation of C1 channels in the presence of internal Ca2+ was irreversible and had a time constant of 1-3 min. This supports our earlier suggestion (Lunevsky et al. 1983) that the inactivation of C1 channels in an intact cell (with a time constant of 1-3 s) is due to a decrease in Ca2+ concentration rather than to the activity of their own inactivation mechanism. The C1 channel selectivity sequence was following: C1- much greater than CH3SO-4 approximately equal to K+ much greater than SO2-4 (PK/PSO4 approximately 10). Activation of one half the channels occurs at a Ca2+ concentration of 2 X 10(-5) mol/l. Sr2+ also (though to a lesser extent) activated C1 channels but had to be present in a much more higher concentration than Ca2+. Mg2+ and Ba2+ appeared ineffective. Ca2+ activation did not, apparently, require participation of water-soluble intermediator including ATP. Thus, C1 channel functioning is controlled by Ca2+-, Sr2+-sensitive elements of the subplasmalemma cytoskeleton.
Asunto(s)
Calcio/farmacología , Cloruros/metabolismo , Eucariontes/fisiología , Canales Iónicos/fisiología , Cationes Bivalentes , Membrana Celular/fisiología , Ácido Egtácico/farmacología , Electrofisiología , Canales Iónicos/efectos de los fármacos , Potenciales de la Membrana , Perfusión , Estroncio/farmacologíaRESUMEN
The present work was intended to further investigate the selective filter of calcium channel on both a cell membrane and reconstructed channels. For the studies on cell membranes, an inhibitor of chloride channels was chosen (ethacrynic acid) to pass currents only through the calcium channels. On both the cells and reconstructed channels, permeability of ions of different crystal radii and valencies was investigated. The obtained results suggest that the channel represents a wide water pore with a diameter larger than 8 A into which ions go together with the nearest water shell. The values of the maximal currents are given by electrostatic interaction of the ions with the anion center of the channel. A phenomenological two-barrier model of the channel is given which describes the movement of all the ions studied.