Biomaterial Database

Mechanisms regulating intracellular pH in sea urchin eggs. 1983

P Payan, and J P Girard, and B Ciapa

Intracellular pH (pHi) of sea urchin eggs (Paracentrotus lividus) was determined using DMO (dimethyloxazolidinedione) and a rapid filtration technique (P. Payan, J.P. Girard, R. Christen and C. Sardet (1981). Exp. Cell Res. 134, 339-344). Transfer of unfertilized or fertilized eggs from normal sea water into Na+-free artificial sea water leads to a progressive acidification and fall of intracellular Na+ content. A step rise in external Na+ to 10 meq causes a rapid but transient Na+ entry coupled to an excretion of H+, giving rise to a pHi increase. It is shown that the plasma membrane of unfertilized eggs contains a permanent and reversible Na+/H+ exchanger which contributes to the regulation of pHi. This exchange occurs with a 1:1 stoichiometry and is independent of metabolic energy. Proton excretion and sodium entry follow saturable kinetics with respect to external Na+ and are completely inhibited by amiloride. At fertilization, pHi increases from 7.38 to 7.64 and is maintained at this level by two separate mechanisms: (1) a Na+/H+ exchange with the same characteristics as in unfertilized eggs; (2) a H+-excreting system that is dependent on external Na+, amiloride sensitive, and requiring metabolic energy. The relationship between the permanent Na+/H+ exchange involved in pHi regulation and the transient Na+/H+ exchange occurring at fertilization is discussed.

UI	MeSH Term	Description	Entries
D007202	Indicators and Reagents	Substances used for the detection, identification, analysis, etc. of chemical, biological, or pathologic processes or conditions. Indicators are substances that change in physical appearance, e.g., color, at or approaching the endpoint of a chemical titration, e.g., on the passage between acidity and alkalinity. Reagents are substances used for the detection or determination of another substance by chemical or microscopical means, especially analysis. Types of reagents are precipitants, solvents, oxidizers, reducers, fluxes, and colorimetric reagents. (From Grant & Hackh's Chemical Dictionary, 5th ed, p301, p499)	Indicator,Reagent,Reagents,Indicators,Reagents and Indicators
D007473	Ion Channels	Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS.	Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D010063	Ovum	A mature haploid female germ cell extruded from the OVARY at OVULATION.	Egg,Egg, Unfertilized,Ova,Eggs, Unfertilized,Unfertilized Egg,Unfertilized Eggs
D011522	Protons	Stable elementary particles having the smallest known positive charge, found in the nuclei of all elements. The proton mass is less than that of a neutron. A proton is the nucleus of the light hydrogen atom, i.e., the hydrogen ion.	Hydrogen Ions,Hydrogen Ion,Ion, Hydrogen,Ions, Hydrogen,Proton
D002462	Cell Membrane	The lipid- and protein-containing, selectively permeable membrane that surrounds the cytoplasm in prokaryotic and eukaryotic cells.	Plasma Membrane,Cytoplasmic Membrane,Cell Membranes,Cytoplasmic Membranes,Membrane, Cell,Membrane, Cytoplasmic,Membrane, Plasma,Membranes, Cell,Membranes, Cytoplasmic,Membranes, Plasma,Plasma Membranes
D004114	Dimethadione	An anticonvulsant that is the active metabolite of TRIMETHADIONE.	5,5-Dimethyl-2,4-oxazolidinedione,5,5-Dimethyloxazolidine-2,4-dione,Dimethyloxazolidinedione
D005260	Female		Females
D005306	Fertilization	The fusion of a spermatozoon (SPERMATOZOA) with an OVUM thus resulting in the formation of a ZYGOTE.	Conception,Fertilization, Delayed,Fertilization, Polyspermic,Conceptions,Delayed Fertilization,Delayed Fertilizations,Fertilizations,Fertilizations, Delayed,Fertilizations, Polyspermic,Polyspermic Fertilization,Polyspermic Fertilizations
D006863	Hydrogen-Ion Concentration	The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH	pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations