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)

1. The effect of treating rats with digoxin and thyroxine for 45 days has been studied. 2. Animals fed with digoxin gained significantly more weight than the control animals. 3. Treatment with digoxin, thyroxine or both produced a similar significant increase in the amount of Na+ + K+ -dependent adenosine triphosphatase in liver without an additive effect. 4. It is suggested that digoxin resistance in thyrotoxicosis may be related to this similarity in action.
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PMID:Rat hepatic sodium plus potassium ion-dependent adenosine triphosphatase after treatment with digoxin and thyroxine. 13 31

Effect of endotoxin from E. coli on the ATP content in heart muscle, the liver and the kidney of thyrotoxic rats was studied. When endotoxin (200-400 micrograms) was intravenously injected to rats taking drinking water containing 2-7.5 micrograms T3 per ml, body temperature rose and the heart rate increased. At the same time, a marked decrease in the ATP content in heart muscle and the kidney was observed together with an increase in Na+-K+-ATPase activity. Such changes were not observed or seen only to a small extent in euthyroid rats after endotoxin administration. Endotoxin-induced ATP depletion in T3-treated rats was prevented by administration of 5 mg hydrocortisone just prior to endotoxin injection. These findings indicate that endotoxin easily causes ATP depletion in some tissue or organs in thyrotoxicosis, even if the dose of endotoxin is not enough to produce such an effect in the euthyroid. These observations are of interest in relation to thyroid storm associated with bacterial infection.
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PMID:Endotoxin-induced ATP depletion in thyrotoxic rats. 295 88

Attention has focused on possible defects at the level of the contractile proteins in myocardial hypertrophy and failure. In small mammals such as the rat and rabbit, myofibrillar and myosin ATPases are depressed in situations of decreased contractility. Converse increases in enzymic activity together with enhanced contractility are seen in the hyperthyroid state. The molecular basis for these changes in enzymic activity is now known to result from transitions in three heavy chain isoenzymes of myosin, V1, V2 and V3 which possess different ATPase activities. Transitions in isoenzyme composition occur during hypertrophy, thyrotoxicosis and development in the myocardium of small mammals. In larger animals such as the rhesus monkey, baboon, cow and in particular, man, only V3, the lowest ATPase isoenzyme can be detected in the normal ventricle and this is the only form present throughout development. Confirmation of the lack of developmental transitions in myosin heavy chains expressed in man is also obtained by sensitive peptide mapping techniques. Changes in myosin heavy chain isoenzymes in large mammals as an explanation of depressed contractile function cannot therefore be made on the presently available evidence. Indeed, evidence for lowered ATPase activities in the failing human myocardium is equivocal. Evidence is however provided for transitions in light chain isoenzymes of myosin in situations of cardiac overload. Caution should be exercised in using small animals as models of myocardial hypertrophy and failure in man.
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PMID:Contractile protein transitions in human cardiac overload: reality and limitations. 624 86

Hypertrophied rabbit heart papillary muscles (thyrotoxicosis), with a high V1/V3 myosin isoenzyme ratio and contractile protein ATPase activity, have a high velocity of unloaded shortening and a decrease in the myothermal economy of isometric twitch force development and dissipation; in hypertrophied hearts (pressure overload) with a low V1/V3 isoenzyme ratio and ATPase activity, the converse was found to be true (Am J Cardiol 1979; 44:947-953; Fed Proc 1982; 41:192-198). In the present study the confounding problem of internal shortening, which takes place during force development and dissipation in the isometric twitch, is minimized by carrying out measurements of the rate of heat liberation during the plateau phase of tetanic force maintenance. The studies are further extended to another species (rat) where the V1/V3 myosin isoenzyme ratio is altered by treating the animal with propyl thiouracil added to the drinking water (PTU); here the contractile protein alteration occurs with myocardial atrophy rather than hypertrophy. High resolution, rapid temperature measurements are made in tetanically stimulated isometrically contracting rat heart papillary muscles from normal (high V1/V3 ratio) and PTU treated (low V1/V3 ratio) rats to assess the relationship between contractile protein performance (crossbridge cycling rate) in the intact muscle and that under controlled conditions in isolated myofibrils. In papillary muscles from the normal heart the crossbridge cycling rate (+/- SEM) during force maintenance was 6.53 (+/- 1.73) cycles/second compared with 3.13 (+/- 0.24) and 0.53 (+/- 0.17) cycles s-1 in the myofibril at high and low ionic strength, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A myothermal analysis of the myosin crossbridge cycling rate during isometric tetanus in normal and hypothyroid rat hearts. 624 98

The structure of the membranes of sarcoplasmic reticulum fragments (SRF) normally and in thyrotoxicosis was studied by the spin-label and spin-probe methods and by chemifluorescence. The curves of temperature dependence of the regularity parameter show a typical break for the spin probe at 20 degrees C shifted by 4 degrees C to sower temperatures for thyrotoxins. The same shift was observed with temperature dependence for the correlation period of the spin label covalently bound to the thiol groups of Ca2+ dependent ATPase of sarcoplasmic reticulum. The latent period of thyrotoxins was reduced and the chemifluorescence intensity increased. The results obtained suggest the occurrence of considerable changes in the structure of SRF membranes in thyrotoxicosis.
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PMID:[Thyroxine: structural transformations in the membranes of rabbit skeletal muscle sarcoplasmic reticulum]. 624 47

Na+-K+ ATPase was measured in euthyroid, hypothyroid, and hyperthyroid rats aged 6 weeks, 6 months, and 20-24 months. There was a small but significant decline in basal enzyme activity with increasing age in renal cortical tissue. Enzyme activity decreased with hypothyroidism and increased with hyperthyroidism. With increasing age, both the magnitude of the increase resulting from thyrotoxicosis and the absolute enzyme level were significantly less with each increase in the age of the experimental animals. Hypothyroid animals displayed no age-related decline in renal cortical Na+-K+ ATPase. The decline in Na+-K+ ATPase in renal cortical tissue is thyroid hormone dependent. In addition, age modifies the response of Na+-K+ ATPase to thyroid hormone.
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PMID:Interaction of age and thyroid hormone status on Na+-K+ ATPase in rat renal cortex and liver. 625 87

The effects of thyrotoxicosis on the contractile properties of soleus muscle were examined in rats given 3 mg of T4 and 1 mg of T3 per kg of diet for 6--8 wk. Thyrotoxicosis induced significant decreases in isometric twitch contraction time (CT), one-half relaxation time, and peak twitch tension. The Ca2+ uptake activity of the sarcoplasmic reticulum (SR) was increased in the thyrotoxic muscles; this adaptation in the SR provides a possible mechanism for the alterations in isometric contractile properties. Thyrotoxicosis induced a large increase in fibers classified as type 2, on the basis of an alkali-stable histochemical reaction for ATPase, in the soleus. Although this reaction is commonly interpreted as indicating that a muscle is fast, maximum shortening velocity (Vmax) and Mg2+ activated actomyosin ATPase activity were unaffected in the thyrotoxic soleus. Our findings provide evidence that CT and Vmax can vary independently and that the histochemical ATPase reaction may not always reflect the biochemical properties that make myosin fast or slow.
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PMID:Contractile, biochemical, and histochemical properties of thyrotoxic rat soleus muscle. 644 99

Thyrotoxicosis in rabbits was induced by prolonged intraperitoneal injection of L-thyroxin. The development of thyroxicosis was assoiated with a decreased Ca2+ accumulation rate by sarcoplasmic reticulum (SR) fragments and a lowered Ca2+ dependent ATPase activity. As compared to the analogous parameters in normal animals. Ca2+ accumulation rate and ATPase activity of thyrotoxicosis animals decreased by 60 and 25%, respectively. The changes in the specific parameters of SR were also observed during incubation of normal SR samples in the medium containing thyroxin (10-5 M). The changes seen in SR functioning in thyrotoxicosis animals are likely to be related to structural rearrangements of lipoprotein surroundings of Ca-ATPase.
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PMID:[Effect of thyroxine on the function of rabbit skeletal muscle sarcoplasmic reticulum]. 644 45

In this paper we review our previous work on the myothermic economy of isometric force production in compensated cardiac hypertrophy secondary to pulmonary artery constriction (pressure overload) and/or thyrotoxicosis (volume overload). Hypertrophy-induced changes in isotonic and isometric twitch mechanics are correlated with accompanying changes in actin-activated myosin ATPase and heat liberation. Heat measurements were made with rapid, high-sensitivity thermopiles on right ventricular papillary muscles from normal and hypertrophied rabbit hearts. Total activity-related heat was separated into initial and recovery heat. Initial heat was separated into a tension-dependent component (TDH) relating to cross-bridge activity, and a tension-independent component (TIH) relating to excitation-contraction coupling. There were oppositely directed changes in most parameters studied in pressure overload hypertrophy (P) as compared with thyrotoxic hypertrophy (T). Thus, in P there was depression (30-50% in the rate of isometric force production, mechanical Vmax, TDH and TDH rate, myosin ATPase, TIH, and prolongation in time-to-peak twitch tension, whereas in T all parameters were oppositely changed except for no change in TIH. Thyrotoxicosis following pressure overload reversed the P-induced changes in all parameters. There was a direct, linear relation between in vitro actin-activated myosin ATPase and in vivo TDH. However, TDH per unit twitch tension or tension-time integral varied inversely with ATPase, making force production more economical than normal in P muscles and less economical than normal in T muscles. These cellular changes beneficially equip P hearts for slow, high-pressure, economical pumping the T hearts for fast, high-volume, uneconomical pumping. The differences are similar to those between slow and fast skeletal muscle and between neonatal and adult skeletal muscle. The mechanism of these changes is discussed in terms of an enzyme kinetic scheme of chemomechanical coupling in actomyosin interaction.
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PMID:Heat, mechanics, and myosin ATPase in normal and hypertrophied heart muscle. 646 Jun 50

Thyroidal trophic effects on slow-twitch skeletal muscle properties were compared in normally innervated and denervated soleus of rats maintained at different thyroid states. Hypothyroidism caused fast to slow changes in fiber type composition (99% decrease in proportion of type II fibers), ATPase activities (down 20-30%), myosin light chain pattern (54% less fast light chains), calcium uptake by SR (down 60%), LDH activity (down 11%), and isozyme pattern (9% decrease in M-subunits). Changes of similar magnitude but opposite in direction were induced by thyrotoxicosis. Denervations reversed, to varying degrees, the fast to slow transformations observed in hypothyroidism. However the slow to fast changes found in hyperthyroidism were facilitated rather than inhibited by denervation. These latter results clearly show that the hormone effect can be elicited in the absence of motor innervation. Furthermore, denervation alone caused slow to fast changes in euthyroid muscles. From these results, it is proposed that denervation and dysthyreosis alter muscle properties by independent mechanisms. Our data favor a direct action of thyroid hormone over a neurally mediated mechanism.
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PMID:Evidence for a direct action of thyroid hormone in specifying muscle properties. 646 Dec 59


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