Biomaterial Database

The activities and concentrations of sodium and potassium in toad oocytes. 1969

D A Dick, and S G McLaughlin

1. The activity of potassium, a(K), in the cytoplasm of oocytes from the toad, Bufo bufo, as measured by potassium-sensitive glass micro-electrodes, was 82 mM. The concentration of potassium, C(K), in oocytes from the same ovaries, as determined by flame photometric analysis, was 113 mM. The ratio a(K)/C(K) = 0.73 does not differ significantly from the measured activity coefficient of the normal Ringer bathing solution, which is 0.75.2. The activity of sodium, a(Na), in the cytoplasm of toad oocytes, as measured by sodium-sensitive glass micro-electrodes, was 9.3 mM. The concentration of sodium, C(Na), in oocytes from the same ovaries, as determined by flame photometric analysis, was 25.8 mM. The value of the a(Na)/C(Na) ratio in the cells, 0.36, is only about half the value of either the a(K)/C(K) ratio in the cells or the activity coefficient of sodium in the normal Ringer bathing solution. This implies that about half the sodium in the cell is sequestered in some manner, such that it is unavailable to affect a cation-sensitive micro-electrode.3. When the oocytes were bathed for 5 hr in a sodium-free, lithium-substituted, Ringer solution the a(Na)/C(Na) ratio decreased to 0.06-0.10. This drop in the a(Na)/C(Na) ratio implies that the sodium available to the cation-sensitive micro-electrode can leave the cell much faster than the sequestered sodium.

UI	MeSH Term	Description	Entries
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D010063	Ovum	A mature haploid female germ cell extruded from the OVARY at OVULATION.	Egg,Egg, Unfertilized,Ova,Eggs, Unfertilized,Unfertilized Egg,Unfertilized Eggs
D010783	Photometry	Measurement of the various properties of light.	Photometries
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D004566	Electrodes	Electric conductors through which electric currents enter or leave a medium, whether it be an electrolytic solution, solid, molten mass, gas, or vacuum.	Anode,Anode Materials,Cathode,Cathode Materials,Anode Material,Anodes,Cathode Material,Cathodes,Electrode,Material, Anode,Material, Cathode
D005260	Female		Females
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001001	Anura	An order of the class Amphibia, which includes several families of frogs and toads. They are characterized by well developed hind limbs adapted for jumping, fused head and trunk and webbed toes. The term "toad" is ambiguous and is properly applied only to the family Bufonidae.	Bombina,Frogs and Toads,Salientia,Toad, Fire-Bellied,Toads and Frogs,Anuras,Fire-Bellied Toad,Fire-Bellied Toads,Salientias,Toad, Fire Bellied,Toads, Fire-Bellied
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23