Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of hypothyroidism and of replacement therapy with T4 or T3 were studied on the enzymatic activities of liver subcellular fractions isolated from Cynomolgus monkeys. Animals were sacrificed 20 days after thyroidectomy. In mitochondria, thyroidectomy decreased significantly the respiratory chain activity (succinate cytochrome c-reductase), the transfer of cytosolic reducing equivalents (glycerol-3-phosphate dehydrogenase) and the phosphorylating capacity (oligomycin-sensitive ATPase and state 3 respiratory rate). The activity of nucleolar and nucleoplasmic RNA polymerases dropped by about 50% in hypothyroid monkeys. In T4 (2.5 micrograms/kg/d) or T3 (1 microgram/kg/d) treated thyroidectomized animals, the iodothyronine concentrations and the activity of mitochondria and nuclei enzymes were halfway between normal and hypothyroid values. Thus, the mitochondrial effects of thyroidectomy in monkey are, as in rat, at least partly secondary to a decrease in nucleocytoplasmic protein synthesis.
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PMID:[Effect of hypothyroidism on mitochondrial energy metabolism and nuclear synthesis of RNA in the liver of Cynomolgus monkeys]. 242 8

The sarcomeric myosin heavy chains (MHCs), which exhibit different levels of ATPase activity, are encoded by a closely related multigene family from which seven members have been identified and characterized in the rat. The MHC genes appear to map to a single chromosome, and at least two of them, alpha- and beta-cardiac, are closely linked in the genome. Each of these genes is approximately 25 kilobases long, and their coding sequences are interrupted by 40 introns. Each MHC gene displays a pattern of expression that is tissue-specific and developmentally regulated, with more than one MHC gene expressed in each muscle and developmental stage. Moreover, with the exception of the extra-ocular muscle MHC gene that has a very specific pattern of expression, the other genes are all expressed in more than one tissue. The expression of all MHC genes can be modulated by thyroid hormone. Surprisingly, however, the same myosin heavy chain gene can be regulated by thyroid hormone in highly different modes, even in opposite directions, depending on the tissue in which it is expressed. Furthermore, the skeletal embryonic and neonatal myosin heavy chain genes, so far considered specific to these two developmental stages, can be re-induced by hypothyroidism in specific adult muscles.
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PMID:Sarcomeric myosin heavy chain gene family: organization and pattern of expression. 242 12

The formation and maintenance of Ca2+-filling levels by sarcoplasmic reticulum vesicles from euthyroid (control) and hypothyroid skeletal muscle were investigated using the Ca2+-indicator quin-2, at [Ca2+] in the medium [( Cao2+]) of 0.05-0.3 microM. Rapid ATP-dependent Ca2+ uptake resulted in a steady-state Ca2+-filling level, Cai2+, within one minute. This Ca2+ gradient was maintained for at least three minutes, during which less than 20% of the ATP was consumed. Cai2+ was maximal (120 nmol/mg) for [Cao2+] greater than 0.3 microM and decreased to 40 nmol/mg at [Cao2+] of 0.05 microM. Preparations from both experimental groups showed qualitatively and quantitatively the same relationship between Cai2+ and [Cao2+] at steady state, despite a significantly lower Ca2+-pump content of hypothyroid sarcoplasmic reticulum, which resulted in a 25% lower maximal (Ca2+ + Mg2+)-ATPase activity. Maintenance of the steady state, at all levels of Cai2+, was associated with net ATP consumption by the Ca2+ pump and cycling of Ca2+, which processes were 30% slower in the hypothyroid group as compared to the control group. Determination of the passive efflux of Ca2+, as well as the fraction of leaky or unsealed sarcoplasmic reticulum fragments, excluded either of these possibilities as an explanation for the relatively high (Ca2+ + Mg2+)-ATPase rates at steady state. On the basis of these and previously reported results, it is concluded that the maintenance of a Ca2+ gradient by sarcoplasmic reticulum under physiological conditions with respect to external [Ca2+] and the concentrations of ATP, ADP and Pi, is associated with the cycling of Ca2+ coupled to net ATP hydrolysis. Using the obtained data it is calculated that the sarcoplasmic reticulum may account for 20% of the resting metabolic rate in skeletal muscle. Consequently, together with the previously reported lower sarcoplasmic reticulum content of skeletal muscle in hypothyroidism, we calculate that about one third of the decrease in basal metabolic rate in this thyroid state can be related to the alterations of the sarcoplasmic reticulum.
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PMID:(Ca2+ + Mg2+)-ATPase activity associated with the maintenance of a Ca2+ gradient by sarcoplasmic reticulum at submicromolar external [Ca2+]. The effect of hypothyroidism. 245 86

Basophilic bodies of skeletal muscles from two patients with hypothyroidism were examined by enzyme histochemistry and ultrastructural study of ultrathin sections stained with periodic-acid-thiocarbohydrazide-silver proteinate for polysaccharides. Some additional characterizations of basophilic bodies were observed: basophilic bodies were found exclusively in type 1 fiber; basophilic bodies were devoid of myofibrillary adenosine triphosphatase, oxidative enzymes, and phosphorylase; and both fibrillary and granular components of basophilic bodies stained strongly for polysaccharides. The polysaccharide nature of basophilic bodies is in keeping with the previous suggestion that the formation of basophilic bodies in hypothyroid patients is related to an impairment of carbohydrate metabolism. Their selective involvement of type 1 fiber and preferential occurrence at the myotendinous junction remain obscure.
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PMID:Basophilic bodies of skeletal muscle in hypothyroidism: enzyme histochemical and ultrastructural studies. 247 44

Myosin ATPase activity is usually considered to reflect the contractile capacity of a given muscle since it correlates with the maximum initial speed of shortening of the unloaded muscle (Vmax). There are several exceptions to this scheme, and it was the goal of this study to determine if the Mg2+-ATPase activity of the covalently bound actomyosin S1 is a more physiological index of contractility. On polyacrylamide gels, the complex obtained after condensation of fast skeletal myosin S1 to skeletal actin is identical to that obtained with myosin S1 from the ventricles of different species, including rat, guinea pig, and human, cross-linked to cardiac or skeletal actin. In every condition, the ATPase activity of the complex is 700-fold higher than that of myosin S1. It correlates linearly with the Vmax both in phylogeny and in conditions in which an isomyosin shift has been reported, such as hypothyroidism and chronic cardiac overload. Such a relation indicates that, in species that already have a low Vmax, a small change in myosin ATPase may induce dramatic consequences in the shortening velocity. Cardiac hypertrophy in humans, where the drop in Vmax is not associated with a myosin change, does not fit into this scheme. The enzymatic activity of the complex is also unmodified in this condition, which shows that, in humans, the myosin ATPase is not a determinant of Vmax and suggests that other mechanisms may be involved. Measurement of this type of ATPase activity provides a new tool to explore contractility biochemically, which is more reproducible and, from a technical point of view, easier to perform than a kinetic assay. It also correlates better with mechanical data obtained with skinned fibers than with those measured on fresh papillary muscles.
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PMID:ATPase activity of the cross-linked complex between cardiac myosin subfragment 1 and actin in several models of chronic overloading. A new approach to the biochemistry of contractility. 252 89

The relation between functional properties of the contractile apparatus, such as shortening velocity and ATPase activity, and myosin isoenzyme composition was studied in ventricular myocardium of adult (60-90-day-old) rats and of newborn (3-day-old) and young (10- and 20-day-old) rats. In adult animals, variations of isomyosin pattern were produced by reducing food intake and by changing the thyroid state. Hyperthyroidism was induced with triiodothyronine daily injection for 15 days; hypothyroidism was induced with iodine-free diet and KClO4 in drinking water for 50-60 days. The following parameters were studied: 1) calcium-magnesium-activated and magnesium-activated ATPase activity of washed and purified myofibrils, 2) calcium-activated ATPase activity of purified myosin, 3) isomyosin composition and relative content of alpha-myosin heavy chains (alpha-MHCs), and 4) force-velocity curve of left and right ventricle papillary muscles. To take into account the difference in excitation-contraction coupling between newborn and adult myocardium, the determination of the force-velocity curve was repeated in Krebs' solution with normal [CaCl2] (2.5 mM) and in Krebs' solution with high [CaCl2] (10 mM). During postnatal growth, the relative content of alpha-MHC increased and reached a maximum at about 20 days. Pronounced increases of myofibrillar and myosin ATPase activity and in shortening velocity occurred during the same period. In adult hyperthyroid rats, alpha-MHC content as well as enzymatic activity and shortening velocity were higher than in control adult animals. Hypothyroidism and food deprivation caused a decrease of alpha-MHC content and a reduction of both enzymatic activities and shortening velocity. The study of the relations between alpha-MHC relative content and functional parameters showed that 1) in ventricular myocardium of adult rats a linear relation existed between alpha-MHC content and myosin and myofibrillar ATPase activity and shortening velocity, and 2) in newborn and young rat ventricular myocardium, both enzymatic activities and shortening velocity were lower than would have been expected on the basis of the linear relation described above. This latter observation could be accounted for by a variation in specific activity of myosin during postnatal development or by the presence of peculiar isomyosins that cannot be detected with usual electrophoretic techniques.
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PMID:Shortening velocity and myosin and myofibrillar ATPase activity related to myosin isoenzyme composition during postnatal development in rat myocardium. 252 95

On the basis of rat model of congenital hypothyroidism, the following problems were investigated: (1) The biochemical changes of DNA amount in cerebrum, and increase of DNA concentration & decline of protein/DNA in cerebellum. (2) The mitochondria ATPase activity of the cells in cerebral cortex was significantly diminished in hypothyroidism, suggesting that energy metabolism of brain was affected by thyroid hormone. (3) The serum T4 level of hypothyroid offsprings was markedly decreased with increase of serum TSH concentration, while the serum T3 content showed no change. However, 131I uptake rate of thyroid was elevated with peak ahead of time in hypothyroid rats. (4) All the hypothyroid rats were accompanied with delayed body weight growth and decreased weight of brain and several other organs. (5) After replacement therapy with thyroid all the indices mentioned above were improved.
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PMID:[Influence of congenital hypothyroidism on the developing rat brain and improvement after thyroid replacement therapy]. 253 92

A number of erythrocyte Na-K ATPase units were measured in 22 patients with hyperthyroid Graves' disease, 3 with primary hypothyroidism, 3 with simple obesity, 13 with chronic renal failure on hemodialysis, and 20 normal controls, using ouabain binding assay as described by DeLuise et al. The number of Na-K ATPase units, derived by maximal binding of 3H-ouabain, was decreased in patients with simple obesity (Mean +/- SD, 0.26 +/- 0.07 pmol/10(9) RBC), as compared with that in normal controls (0.39 +/- 0.10), and a significant negative correlation between the number of the binding sites and the ratio of the measured body weight to the optimal body weight calculated by the modified Broca's method was observed in normal controls and patients with obesity (r = -0.51, p less than 0.05). The results agreed closely with that reported by DeLuise et al and provided validation of our estimates of the erythrocyte Na-K pump units. The maximal 3H-ouabain binding was significantly diminished in patients with hyperthyroid Graves' disease (0.28 +/- 0.07) when compared with that in normal controls, while the bindings were significantly elevated in patients with hypothyroidism (0.91 +/- 0.26). These results were in disagreement with those previously reported by animal studies where Na-K ATPase was found to be stimulated by thyroid hormones. It might be possible to partly explain this discrepancy by the degradation of Na-K ATPase in erythrocytes in addition to the apparent differences between erythrocytes and the other tissues and by the length of time that the tissue was exposed to the action of the hormones. Therefore, erythrocyte from normal controls and patients with hyperthyroid Graves' disease were divided into low and high density portions by a discontinuous 'percoll' density gradient centrifugation, and the bindings of the erythrocytes in two portions were separately measured. The bindings of erythrocyte in the higher density portion, representing relatively old-aged erythrocyte, were diminished to 92 +/- 19% of the bindings of the original whole erythrocytes in normal controls. An even more marked reduction of the maximal bindings of 3H-ouabain in old-aged erythrocytes was observed in patients with hyperthyroid Graves' disease (72 +/- 26%). Moreover, this % reduction based on aging related significantly to serum T4 concentrations in those patients (r = 0.85, p less than 0.05). These findings suggest that the number of erythrocyte Na-K ATPase units may reflect the overall peripheral metabolic state, regulated by thyroid hormone-dependent thermogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:[Clinical studies on assay for Na-K ATPase in human blood cells. I. Erythrocyte Na-K ATPase assay in patients with thyroid dysfunction and in those with chronic renal failure]. 284 3

The brain contains two molecular forms of Na,K-ATPase designated alpha found in non-neuronal cells and neuronal soma and alpha + found in axolemma. Previously we have shown that the abundance of both forms (determined by immunoblots) as well as Na,K-ATPase activity increases 10-fold between 4 days before and 20 days after birth (Schmitt, C. A., and McDonough, A. A. (1986) J. Biol. Chem. 261, 10439-10444). Hypothyroidism in neonates blunts these increases. Neonatal, but not adult brain Na,K-ATPase is thyroid hormone (triiodothyronine, T3) responsive. This study defines the period during which brain Na,K-ATPase responds to T3. The start of the critical period was defined by comparing Na,K-ATPase activity and alpha and alpha + abundance in hypothyroid and euthyroid neonates (birth to 30 days of age). For all parameters, euthyroid was significantly higher by 15 days of age. The end of the critical period was defined by dosing hypothyroid neonates with T3 daily (0.1 micrograms/g body weight) beginning at increasing days of age, and sacrificing all at 30 days then assaying enzyme activity and abundance. Those starting T3 treatment on or before day 19 were restored to euthyroid levels of Na,K-ATPase activity and abundance, while those starting T3 treatment on or after day 22 remained at hypothyroid levels of enzyme activity and abundance. We conclude that brain Na,K-ATPase alpha and alpha + isoforms are sensitive to T3 by as late as 15 days of age and that the period of thyroid hormone responsiveness is over by 22 days.
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PMID:Thyroid hormone regulates alpha and alpha + isoforms of Na,K-ATPase during development in neonatal rat brain. 284 74

The cardiac myofibrillar component of the phosphorylcreatine shuttle mechanism enzymatically couples the functionally significant processes of energy utilization (ATPase) with substrate regeneration by creatine kinase (CK). Both components have isoenzyme forms that are transcriptionally regulated. Propylthiouracil-induced (PTU) hypothyroidism reduced rat cardiac contractile protein ATPase activity by shifting isomyosin predominance from the V1 to the V3 form. However, neither CK specific activity or CK isoenzyme composition was altered by PTU treatment. Thus, myofibrillar components of the phosphorylcreatine shuttle, ATPase and CK, are not coordinately regulated under hypothyroid conditions.
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PMID:Cardiac myofibrillar creatine kinase is not influenced by hypothyroidism. 293 Nov 68


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