Mechanism for increase in intracellular concentration of free calcium in fertilized sea urchin egg. A method for estimating intracellular concentration of free calcium

M. Nakamura, I. Yasumasu

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    Abstract

    Intracellular free calcium concentration in the sea urchin egg was calculated to increase from 0.1 mM in an unfertilized egg to 1 mM in a fertilized egg 10 min after fertilization, based on measurement of the dissociation constant between free calcium and sea urchin egg homogenate. The dissociation constant between free calcium (dialyzable calcium) and homogenate of sea urchin eggs was measured by means of dialysis equilibrium. The dissociation constant of the unfertilized egg was about 10-4 M and that of the fertilized egg was about 10-3 M in 3 species of sea urchin, Hemicentrotus pulcherrimus, Anthocidaris crassispina, and Pseudocentrotus depressus. An increase in the dissociation constant of the unfertilized egg homogenate was observed after the addition of calcium ion at a concentration above 0.3 mM, the dissociation constant becoming the same as that observed in the fertilized egg homogenate after the administration of CaCl2 at a concentration above 1 mM. Sodium ion also caused a decrease in the calcium binding ability of the unfertilized egg homogenate. Therefore, penetration of calcium ion or sodium ion upon fertilization might induce an increase in the dissociation constant and then intracellular concentration of free calcium would increase at fertilization. Almost all calcium binding ability of the egg homogenate was found in the microsomal fraction, and the substance which bound calcium was thought to be protein in nature, since trypsin could decrease the level of calcium binding substance in the homogenate of the eggs.

    Original languageEnglish
    Pages (from-to)374-388
    Number of pages15
    JournalJournal of General Physiology
    Volume63
    Issue number3
    Publication statusPublished - 1974

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    Sea Urchins
    Ovum
    Calcium
    Zygote
    Fertilization
    Ions
    Eggs
    Anthocidaris
    Hemicentrotus
    Sodium
    Trypsin
    Dialysis

    ASJC Scopus subject areas

    • Physiology

    Cite this

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    abstract = "Intracellular free calcium concentration in the sea urchin egg was calculated to increase from 0.1 mM in an unfertilized egg to 1 mM in a fertilized egg 10 min after fertilization, based on measurement of the dissociation constant between free calcium and sea urchin egg homogenate. The dissociation constant between free calcium (dialyzable calcium) and homogenate of sea urchin eggs was measured by means of dialysis equilibrium. The dissociation constant of the unfertilized egg was about 10-4 M and that of the fertilized egg was about 10-3 M in 3 species of sea urchin, Hemicentrotus pulcherrimus, Anthocidaris crassispina, and Pseudocentrotus depressus. An increase in the dissociation constant of the unfertilized egg homogenate was observed after the addition of calcium ion at a concentration above 0.3 mM, the dissociation constant becoming the same as that observed in the fertilized egg homogenate after the administration of CaCl2 at a concentration above 1 mM. Sodium ion also caused a decrease in the calcium binding ability of the unfertilized egg homogenate. Therefore, penetration of calcium ion or sodium ion upon fertilization might induce an increase in the dissociation constant and then intracellular concentration of free calcium would increase at fertilization. Almost all calcium binding ability of the egg homogenate was found in the microsomal fraction, and the substance which bound calcium was thought to be protein in nature, since trypsin could decrease the level of calcium binding substance in the homogenate of the eggs.",
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    T1 - Mechanism for increase in intracellular concentration of free calcium in fertilized sea urchin egg. A method for estimating intracellular concentration of free calcium

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    AU - Yasumasu, I.

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    AB - Intracellular free calcium concentration in the sea urchin egg was calculated to increase from 0.1 mM in an unfertilized egg to 1 mM in a fertilized egg 10 min after fertilization, based on measurement of the dissociation constant between free calcium and sea urchin egg homogenate. The dissociation constant between free calcium (dialyzable calcium) and homogenate of sea urchin eggs was measured by means of dialysis equilibrium. The dissociation constant of the unfertilized egg was about 10-4 M and that of the fertilized egg was about 10-3 M in 3 species of sea urchin, Hemicentrotus pulcherrimus, Anthocidaris crassispina, and Pseudocentrotus depressus. An increase in the dissociation constant of the unfertilized egg homogenate was observed after the addition of calcium ion at a concentration above 0.3 mM, the dissociation constant becoming the same as that observed in the fertilized egg homogenate after the administration of CaCl2 at a concentration above 1 mM. Sodium ion also caused a decrease in the calcium binding ability of the unfertilized egg homogenate. Therefore, penetration of calcium ion or sodium ion upon fertilization might induce an increase in the dissociation constant and then intracellular concentration of free calcium would increase at fertilization. Almost all calcium binding ability of the egg homogenate was found in the microsomal fraction, and the substance which bound calcium was thought to be protein in nature, since trypsin could decrease the level of calcium binding substance in the homogenate of the eggs.

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