Effect of neonatal hypothyroidism on the kinetic properties of Na+, K+ -ATPase from rat brain microsomes. 2006

S S Katyare, and F R Billimoria, and B N Dave
Department of Biochemistry, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara, Gujarat, India. sskatyare_msu2001@yahoo.com

The effects of neonatal hypothyroidism on the kinetic properties of Na+, K+ -ATPase from rat brain microsomes were examined. Neonatal hypothyroidism resulted in decreased Na+, K+ -ATPase activity compared to control samples (7.4 +/- 1.48 and 29.8 +/- 2.30 micromol Pi/h/mg protein, respectively, P < 0.001). Substrate kinetics studies with ATP, Na+ and K+ revealed that there were generalised decreases in Vmax. For ATP, Na+ and K+, activities resolved into two kinetic components in the control group. In hypothyroid animals, the low-affinity component for ATP was absent. The opposite pattern (i.e. an absence of the high-affinity component) was noted for Na+. For K+, although both kinetic components were discernible in neonatal hypothyroid brain microsomes, the Km of the high-affinity component was significantly higher (P < 0.001) compared to control samples. In the control group, the enzyme displayed allosteric behaviour at high concentrations of Mg2+; in hypothyroid animals, the pattern was completely allosteric. The Na+, K+ -ATPase enzyme from the hypothyroid brain microsomes bound two molecules of ATP rather than one, unlike in the control animals. Our results thus indicate that neonatal hypothyroidism results in an impairment of microsomal Na+, K+ -ATPase activity in the rat brain, together with subtle alterations in the kinetic properties of the enzyme.

UI MeSH Term Description Entries
D007037 Hypothyroidism A syndrome that results from abnormally low secretion of THYROID HORMONES from the THYROID GLAND, leading to a decrease in BASAL METABOLIC RATE. In its most severe form, there is accumulation of MUCOPOLYSACCHARIDES in the SKIN and EDEMA, known as MYXEDEMA. It may be primary or secondary due to other pituitary disease, or hypothalamic dysfunction. Central Hypothyroidism,Primary Hypothyroidism,Secondary Hypothyroidism,TSH Deficiency,Thyroid-Stimulating Hormone Deficiency,Central Hypothyroidisms,Deficiency, TSH,Deficiency, Thyroid-Stimulating Hormone,Hormone Deficiency, Thyroid-Stimulating,Hypothyroidism, Central,Hypothyroidism, Primary,Hypothyroidism, Secondary,Hypothyroidisms,Primary Hypothyroidisms,Secondary Hypothyroidisms,TSH Deficiencies,Thyroid Stimulating Hormone Deficiency,Thyroid-Stimulating Hormone Deficiencies
D007700 Kinetics The rate dynamics in chemical or physical systems.
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
D004789 Enzyme Activation Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1, activation by ions (activators); 2, activation by cofactors (coenzymes); and 3, conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. Activation, Enzyme,Activations, Enzyme,Enzyme Activations
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
D000831 Animals, Newborn Refers to animals in the period of time just after birth. Animals, Neonatal,Animal, Neonatal,Animal, Newborn,Neonatal Animal,Neonatal Animals,Newborn Animal,Newborn Animals
D013574 Synaptosomes Pinched-off nerve endings and their contents of vesicles and cytoplasm together with the attached subsynaptic area of the membrane of the post-synaptic cell. They are largely artificial structures produced by fractionation after selective centrifugation of nervous tissue homogenates. Synaptosome
D051381 Rats The common name for the genus Rattus. Rattus,Rats, Laboratory,Rats, Norway,Rattus norvegicus,Laboratory Rat,Laboratory Rats,Norway Rat,Norway Rats,Rat,Rat, Laboratory,Rat, Norway,norvegicus, Rattus

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