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Title: Calcium-activated potassium-channels in mammalian eggs
Author: Georgiou, Panayiotis Paulou
ISNI:       0000 0001 3494 8877
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1985
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Intracellular microelectrode recordings from zonafree hamster eggs revealed a mean value for the membrane potential of -34+9mV (mean ± SD, n=36) and a mean value for the input resistance of 290±170MΩ.(mean ± SD) . Ionophoretic injection of calcium ions into a hamster egg caused a marked membrane hyperpolarization (mean ± SD = 27±9mV, n=63) which was associated with a large reduction in the egg input resistance (viz. from 140±94MΩ prior to the injection to 40±24MΩ at the peak of the response, n=63). The estimated reversal potential of the calcium-evoked hyperpolarization was found to be -69±11mV (mean ± SD,n=63). The mean slope of the relation between the reversal potential and log₁₀[ᴷ⁺]ₒ was 50mV in good agreement with the value predicted by the Nernst equation for a rise in conductance primarily selective for potassium ions. In addition the reversal potential was unaffected by about a tenfold reduction in the concentration of external chloride. It is concluded that the calcium-evoked hyperpolarization was caused by the opening of membrane potassium channels that are activated by an increase in the intracellular concentration of ionized free calcium. The duration of the calcium-evoked response was markedly extended in the presence of ImM external lanthanum or 20mM calcium or by external application of 0.2-2mM 2,4,dinitrophenol. Double microelectrode experiments identified the presence of an impalement leak artifact which might cause an underestimate of the true membrane potential and input resistance. Evidence is also presented for a second type of artifact, namely the generation of a leak conductance pathway during the passage of large depolarizing current pulses (>10nA, 1 sec) used for the ionophoretic injection of calcium into cells.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Human anatomy & human histology