Potassium Channels in Eremosphaera viridis: Modulation of Channel Opening,Conductance and Inhibition* |
| |
Authors: | K Khler B Frster J Kolbowski |
| |
Institution: | K. Köhler,B. Förster,J. Kolbowski |
| |
Abstract: | I/V relationships were performed by the voltage clamp technique in the sphaerical green alga Eremosphaera viridis de Bary. We focused on the course of the transient potential (TP) found in light-off experiments when specific potassium channels open. I/V measurements done during this period show a N-shaped curve. The shape depended on external potassium. TPs could be released by light-off and by addition of barium, strontium, or α-naphthyl phosphate. We calculated the number of specific potassium channels to be between 1750 and 34 825 channels per cell. Barium (1 mol × m?3) and tetraethylammonium (10 mol × m?3) inhibited TPs. I/V relationships demonstrated, when N-shaped, that potassium channels start to close at voltages more negative than ?195 mV (0.1 mol × m?3 K+), ?160 mV (1 mol × m?3 K+) and ?148 mV (10 mol × m?3 K+). In the region of ?300 mV conditions similar to those at rest are reached. External sodium suppressed the development of N-shaped I/V relationships and reduced the membrane conductance during a TP between 8 % and 29 %. This indicates an influence of external sodium on potassium channels. |
| |
Keywords: | Eremosphaera viridis TEA barium voltage-dependent closing of potassium channels Na+ block α -naphthyl phosphate I/V curve voltage clamp |
|
|