Biomaterial Database

Limited binding capacity sites for L-triiodothyronine in rat liver nuclei. Nuclear-cytoplasmic interrelation, binding constants, and cross-reactivity with L-thyroxine. 1974

J H Oppenheimer, and H L Schwartz, and D Koerner, and M I Surks

Further studies have been performed to define the kinetic characteristics of nuclear triiodothyronine (T(3)) binding sites in rat liver (J. Clin. Endocrinol. Metab. 1972. 35: 330). Sequential determination of labeled T(3) associated with nuclei and cytoplasm over a 4-h period allowed analysis of the relationship of T(3) in nuclear and cytoplasmic compartments. A rapid interchange of hormone between nuclei and cytoplasm was demonstrated, and in vitro incubation experiments with nuclei yielded no evidence favoring metabolic transformation of T(3) by the nuclei. In vivo displacement experiments were performed by subcellular fractionation of liver (1/2) h after injection of [(125)I]T(3) with increasing quantities of unlabeled T(3). The nuclear binding capacity for T(3) could be defined (0.52 ng/mg DNA). Analysis of these experiments also allowed an estimation of the association constant of nuclear sites for T(3) (4.7 x 10(11)M(-1)). The affinity of these sites for T(3) was estimated to be 20-40 fold greater than for thyroxine (T(4)). Chromatographic analysis of the nuclear radioactivity after injection of labeled T(4) indicated that the binding of T(4) by the nucleus could not be attributed to in vivo conversion of T(4) to T(3) but reflected intrinsic cross-reactivity of the two iodothyronines at the nuclear binding sites.

UI	MeSH Term	Description	Entries
D007457	Iodine Radioisotopes	Unstable isotopes of iodine that decay or disintegrate emitting radiation. I atoms with atomic weights 117-139, except I 127, are radioactive iodine isotopes.	Radioisotopes, Iodine
D008099	Liver	A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances.	Livers
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D011485	Protein Binding	The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.	Plasma Protein Binding Capacity,Binding, Protein
D011863	Radioimmunoassay	Classic quantitative assay for detection of antigen-antibody reactions using a radioactively labeled substance (radioligand) either directly or indirectly to measure the binding of the unlabeled substance to a specific antibody or other receptor system. Non-immunogenic substances (e.g., haptens) can be measured if coupled to larger carrier proteins (e.g., bovine gamma-globulin or human serum albumin) capable of inducing antibody formation.	Radioimmunoassays
D002458	Cell Fractionation	Techniques to partition various components of the cell into SUBCELLULAR FRACTIONS.	Cell Fractionations,Fractionation, Cell,Fractionations, Cell
D002467	Cell Nucleus	Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)	Cell Nuclei,Nuclei, Cell,Nucleus, Cell
D002854	Chromatography, Paper	An analytical technique for resolution of a chemical mixture into its component compounds. Compounds are separated on an adsorbent paper (stationary phase) by their varied degree of solubility/mobility in the eluting solvent (mobile phase).	Paper Chromatography,Chromatographies, Paper,Paper Chromatographies
D003593	Cytoplasm	The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990)	Protoplasm,Cytoplasms,Protoplasms