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Development of K+-Conductance and Membrane Potentials in Unfertilized Sea Urchin Eggs after Exposure to NH4OH


THE fertilization of the sea urchin egg starts a sequence of changes in the cell membrane which can be measured as changes of membrane potential and membrane resistance1–3. The immediate consequence of contact of ovum and spermatozoon is an action potential, a depolarization and repolarization including a transient reversal of polarity. The overall sequence1,2 converts the anion-permeable membrane of the unfertilized egg (with a potential of about −10 mV, inside negative) to a rather typical K+ permeable membrane (about −60 mV, inside negative). The same results are obtained with parthenogenetic activation of the egg.

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STEINHARDT, R., MAZIA, D. Development of K+-Conductance and Membrane Potentials in Unfertilized Sea Urchin Eggs after Exposure to NH4OH. Nature 241, 400–401 (1973).

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