Internal calcium concentration and potassium permeability in Paramecium.
Ca or EGTA was ionophoretically injected into Paramecium tetraurelia to change [Ca]i. Ca decreased the resting membrane resistance and hyperpolarized the membrane. EGTA had the opposite effect. EGTA following TEA, which suppress GK, had little effect on resistance or resting potential. The I-V relation at steady state was studied before and after EGTA injection while the cell bathed in either K- or TEA-solution. The response to inward test pulses after EGTA injection was similar to that after TEA injection. These results show that [Ca]i controls a steady-state K permeability in Paramecium tetraurelia. A prolonged Ca-spike was recorded after EGTA injection. The plateau potentials in various Ca concentrations in a TEA-solution show the Nernst slope (29 mV for tenfold change in [Ca]o). This result suggests that the prolonged depolarization in this condition is due to a Ca current, after suppression of K-permeability and when [Ca]i is low. The difficulty of obtaining quantitative data on the internal Ca, and the difference between the effects of EGTA injection and TEA injection are discussed.
D002118:Calcium / Q000032:analysis* / Q000494:pharmacology; D002463:Cell Membrane Permeability; D004533:Egtazic Acid / Q000494:pharmacology; D010247:Paramecium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*
D004533:Egtazic Acid; D011188:Potassium; D002118:Calcium