Biomaterial Database

Characterization of a very-high-affinity ouabain binding site in term fetal guinea pig brain Na+,K(+)-ATPase. 1998

E M Graham, and O P Mishra, and M Delivoria-Papadopoulos

Department of Obstetrics and Gynecology, Allegheny University of the Health Sciences, Philadelphia, Pennsylvania, USA.

OBJECTIVE To characterize the very-high-affinity ouabain binding site in fetal brain and determine its sensitivity to hypoxia. METHODS Studies were performed on six normoxic and six hypoxic guinea pig fetuses at term and in six adult guinea pigs. Fetuses were delivered after the pregnant female had been exposed to 21% or 7% oxygen for 1 hour. Brain cell membranes were prepared and ouabain binding studies were performed. Ouabain binding was determined in the presence and absence of erythrosin B, a known inhibitor of high-affinity ouabain binding sites. RESULTS Normoxic term fetal brain membrane had a Bmax (receptor number) of 84.2 +/- 13.6 pmol/mg protein, which decreased to 5.9 +/- 3.8 pmol/mg protein (93.0% decrease, P < .001) in the presence of erythrosin B. Normoxic fetal brain had a dissociation constant (Kd) (receptor affinity) of 24.6 +/- 4.5 nmol/L, which was unchanged in the presence of erythrosin B (Kd = 20.7 +/- 15.4 nmol/L, P = nonsignificant [NS]). Hypoxic term fetal brain had a Bmax of 74.7 +/- 8.3 pmol/mg protein, which decreased to 7.1 +/- 3.9 pmol/mg protein (90.5% decrease, P < .001) in the presence of erythrosin B. Hypoxic fetal brain had a Kd of 22.9 +/- 1.9 nmol/L, which was unchanged in the presence of erythrosin B (Kd = 24.5 +/- 9.9 nmol/L, P = NS). The adult control guinea pig brain had a Bmax of 104.1 +/- 13.3 pmol/mg protein, which decreased to 44.9 +/- 10.5 pmol/mg protein (P < .001) in the presence of erythrosin B, and a Kd of 214.3 +/- 31.3 nmol/L, which remained unchanged in the presence of erythrosin B (Kd was 165.4 +/- 36.0 nmol/L, P = NS). CONCLUSIONS Fetal brain has a unique very-high-affinity ouabain binding site that is absent in adult brain and is sensitive to erythrosin B and resistant to hypoxia. We speculate that the presence of a Na+,K(+)-ATPase molecule with a very-high-affinity site may be advantageous to the fetal brain during early maturation as well as during hypoxia or ischemia.

UI	MeSH Term	Description	Entries
D008565	Membrane Proteins	Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.	Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D010042	Ouabain	A cardioactive glycoside consisting of rhamnose and ouabagenin, obtained from the seeds of Strophanthus gratus and other plants of the Apocynaceae; used like DIGITALIS. It is commonly used in cell biological studies as an inhibitor of the NA(+)-K(+)-EXCHANGING ATPASE.	Acocantherin,G-Strophanthin,Acolongifloroside K,G Strophanthin
D011247	Pregnancy	The status during which female mammals carry their developing young (EMBRYOS or FETUSES) in utero before birth, beginning from FERTILIZATION to BIRTH.	Gestation,Pregnancies
D001921	Brain	The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.	Encephalon
D004305	Dose-Response Relationship, Drug	The relationship between the dose of an administered drug and the response of the organism to the drug.	Dose Response Relationship, Drug,Dose-Response Relationships, Drug,Drug Dose-Response Relationship,Drug Dose-Response Relationships,Relationship, Drug Dose-Response,Relationships, Drug Dose-Response
D005260	Female		Females
D006168	Guinea Pigs	A common name used for the genus Cavia. The most common species is Cavia porcellus which is the domesticated guinea pig used for pets and biomedical research.	Cavia,Cavia porcellus,Guinea Pig,Pig, Guinea,Pigs, Guinea
D000254	Sodium-Potassium-Exchanging ATPase	An enzyme that catalyzes the active transport system of sodium and potassium ions across the cell wall. Sodium and potassium ions are closely coupled with membrane ATPase which undergoes phosphorylation and dephosphorylation, thereby providing energy for transport of these ions against concentration gradients.	ATPase, Sodium, Potassium,Adenosinetriphosphatase, Sodium, Potassium,Na(+)-K(+)-Exchanging ATPase,Na(+)-K(+)-Transporting ATPase,Potassium Pump,Sodium Pump,Sodium, Potassium ATPase,Sodium, Potassium Adenosinetriphosphatase,Sodium-Potassium Pump,Adenosine Triphosphatase, Sodium, Potassium,Na(+) K(+)-Transporting ATPase,Sodium, Potassium Adenosine Triphosphatase,ATPase Sodium, Potassium,ATPase, Sodium-Potassium-Exchanging,Adenosinetriphosphatase Sodium, Potassium,Pump, Potassium,Pump, Sodium,Pump, Sodium-Potassium,Sodium Potassium Exchanging ATPase,Sodium Potassium Pump
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