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

---

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

It has been recognized for a long time that changes in hormone secretion can influence cardiac function; however, the biochemical basis for these changes has only recently been clarified. In this review the influences of hormonal status on the contractile protein myosin is discussed. Myosin has a rod-like portion and a globular head and consists of two myosin heavy chains (MHC) and four light chains (LC), two of which are identical. The globular head is the site of an ATP-splitting enzyme, the myosin ATPase, and increases in myosin ATPase activity are closely related to an increased velocity of contraction of the heart. Myosin ATPase activity shows marked response to alterations in thyroid hormone, insulin, glucocorticoid, testosterone and catecholamine levels, but marked animal species differences in this response occur. Thyroid hormone administration to normal rabbits, for example, increases myosin ATPase activity markedly, but the myosin ATPase activity of hyperthyroid rats remains unchanged. In contrast, in hypothyroid rats myosin ATPase activity is markedly decreased but the hypothyroid rabbit shows no such response. These species-related differences in the hormonal response of myosin ATPase activity result from the predominance pattern of specific myosin isoenzymes. In the normal rat heart three myosin isoenzymes, V1, V2 and V3, can be separated electrophoretically. Myosin V1 predominates (70% of total myosin), and has the highest myosin ATPase activity, whereas in rabbits myosin V3, which has a lower myosin ATPase activity, is the predominant isomyosin. Thyroid hormone administration to rabbits induces myosin V1 predominance and therefore increases myosin ATPase activity, whereas in hyperthyroid rats only a small further increase in V1 predominance can occur. The alterations in myosin isoenzyme predominance and myosin ATPase activity are closely correlated to changes in cardiac contractility. Hormone-induced alterations in myosin isoenzyme predominance are mediated through changes in the formation of two isoforms of myosin heavy chain. Changes in the expression of different myosin heavy chain genes are most likely responsible for the thyroid hormone and insulin-induced alterations in myosin isoenzyme predominance. Investigation of the control of myosin heavy chain formation can provide further insights into the hormonal control of a multigene family as well as broaden our understanding of the molecular events which result in altered cardiac contractility.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Hormonal influences on cardiac myosin ATPase activity and myosin isoenzyme distribution. 623 63

The paper reports on the relationship between spectrin-dependent ATPase and erythrocyte shape. It can be seen from various experiments that different treatment of erythrocyte membrane which brings about alteration in activity of spectrin-dependent ATPase, also changes erythrocyte shape. We suggest that spectrin-dependent ATPase is a large actomyosin-like protein complex with some characteristics of contractile protein which, under suitable conditions, causes a physiological tension (contraction) of the membrane. Energetically rich state of spectrin-dependent ATPase seems to be responsible for this phenomenon.
...
PMID:The role of spectrin-dependent ATPase in erythrocyte shape maintenance. 623 27

Electrophoretic and enzyme techniques have been used to study the structure and function of the contractile protein system in the myocardium of dogs before and after beta-adrenoceptor blockade. Animals were examined after acute beta-adrenoceptor blockade by using intravenous atenolol (0.2 mg/kg) and following chronic therapy with oral atenolol (100 mg twice daily) for a mean period of 106 days. Two-dimensional polyacrylamide-gel electrophoretic techniques were used to examine the myocardial contractile and regulatory proteins present in endomyocardial biopsy specimens obtained after acute and chronic beta-adrenoceptor blockade. No differences in charge, molecular weight or the relative proportions of actin, myosin light chains, tropomyosin or troponin-C were seen after either acute or chronic beta-adrenoceptor blockade. The maximal activity and calcium sensitivity of the myofibrillar adenosine triphosphatase (ATPase) was also unchanged after acute and chronic atenolol therapy. It is concluded that beta-adrenoceptor blockade has no significant adaptive effect on the structural or functional properties of the myofibril.
...
PMID:The effects of acute and chronic beta-adrenoceptor blockade on the myofibrillar contractile system in the dog heart. 623 83

Diabetes mellitus causes congestive heart failure in humans, independent of atherosclerosis. The present study extends previous work on the reversibility, with insulin, of the alterations in myocardial function and contractile protein biochemistry observed in diabetic rats. The response of these alterations to different fixed doses of insulin was explored. Diabetic rats were given 0, 0.5, 1, 1.5, 2, or 2.5 U of insulin daily for 6 wk. Papillary muscle function, actomyosin ATPase, and myosin isoenzyme distribution showed progressive normalization with increasing insulin dose as blood glucose concentration returned to normal. Thus insulin therapy in diabetic rats on a normal diet produces continuous improvement in cardiac function and biochemistry as euglycemia is approached. This study also suggests that mild diabetes results in qualitatively identical, although quantitatively less pronounced, myocardial changes compared with those observed in severely diabetic rats.
...
PMID:Diabetic cardiomyopathy in rats: mechanical and biochemical response to different insulin doses. 623 41

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)
...
PMID:A myothermal analysis of the myosin crossbridge cycling rate during isometric tetanus in normal and hypothyroid rat hearts. 624 98

Recent work on vascular smooth muscle actomyosin has indicated that the Ca2+ sensitivity of both ATPase and superprecipitation are affected by calmodulin (CaM) and cyclic AMP-dependent protein kinase (cPK). Using a "chemically skinned" arterial preparation, we have extended these observations to the intact structured contractile system. Media from hog carotid artery were skinned with 1% Triton X-100 followed by a 50% glycerol-ATP salt solution, in which the strips were stored at -25 degrees C. Small strips (thickness between 0.1 and 0.2 mm) were mounted isometrically and relaxed in a Mg-ATP salt solution, pH 6.7, Ca2+ 10(-8) M, 30 degrees C. Ca2+ elicited a contraction with an ED50 of 10(-6) M. Isometric force was between 1 and 4 mN, consistent with the force observed before skinning. With time, the preparation became less sensitive with an increase in ED50 to 10(-5.7) M. CaM (4 micro M) reverses this loss, stabilizes the preparation, and sharply accelerates the rate of tension development. The ED50 in the presence of 4 micro M CaM shifts to about 10(-7) M. This effect is dose-dependent, with the half maximal effect at about 0.4 micro M CaM. Submaximal Ca2+ contractions can be reversibly depressed by preincubation of relaxed fibers with cPK catalytic subunit (300 U/ml), even in the presence of 4 micro M CaM. An inhibition of about 50% of the contraction at 0.2 micro M Ca2+ was obtained, whereas only 20% inhibition was found at 6 micro M Ca2+. Our findings suggest that changes in vascular contractility cannot be described solely in terms of changes in cytoplasmic Ca2+, and that changes in the sensitivity of the contractile protein to a given Ca2+ concentration are also potential mechanisms for vasodilation.
...
PMID:Vascular smooth muscle. Calmodulin and cyclic AMP-dependent protein kinase after calcium sensitivity in porcine carotid skinned fibers. 627 27

Male Fischer 344 rats were subjected to regular forced exercise beginning at weaning and continued until sacrificed at ages ranging from 2 to 18 months. Littermates served as sedentary controls. At all ages examined, the exercised animals had greater heart and lower body weights. Actomyosin was isolated from the myocardium and the ATPase activity of the contractile protein preparation was measured. Only the sedentary animals exhibited an age-related loss in enzyme activity. The physically trained animals had substantially higher ATPase specific activity than the controls at all ages. This difference in ATPase specific activity may be the result of the synthesis of different isozymic forms of myosin or changes in the regulatory proteins of actomyosin (tropomyosin and troponin). It is suggested that lifelong regular exercise may alter the known biochemical changes in the heart muscle that relate to declining cardiac function.
...
PMID:Effects of exercise on the biochemical aging of mammalian myocardium. I. Actomyosin ATPase. 645 50

To study effects of physiologic hypertrophy on contractile protein ATPases and sarcoplasmic reticulum, hypertrophy was caused in female Wistar rats by a chronic swimming program. Nonhypertrophied hearts of female control sedentary rats and rats made to run on a treadmill program were also examined. The swimming program, but not the running program, resulted in a significant increase in heart weight. Actomyosin ATPase activity was also increased by 15% in the hearts of swimmers but not runners. Similar increases were observed for Ca2+-activated myosin ATPase activity and actin-activated ATPase of myosin. Sarcoplasmic reticulum from the hearts of swimmers showed increased calcium binding and calcium uptake as a function of time and of calcium concentration. Sarcoplasmic reticulum ATPase activities were not altered by hypertrophy. These findings in physiologic hypertrophy contrast with those of pathologic hypertrophy in which ATPase activity of contractile proteins and calcium binding and uptake of sarcoplasmic reticulum have generally been found to be depressed.
...
PMID:Contractile proteins and sarcoplasmic reticulum in physiologic cardiac hypertrophy. 645 23

In order to determine whether diabetic cardiomyopathy in rats is associated with altered contractile proteins, male and female rats were made diabetic with intravenous streptozotocin (STZ). Calcium ATPase activity of cardiac actomyosin was significantly decreased after 1 week of diabetes and was depressed by 60% by 2 weeks. Rats pretreated with 3-O-methyl glucose to prevent the hyperglycemia caused by STZ had normal Ca2+-actomyosin ATPase activities, and non-diabetic rats whose food was restricted to keep their body and heart weights similar to those found in diabetic animals had only a slight fall in actomyosin ATPase activity. Ca2+-ATPase and actin-activated ATPase activities of pure myosin were similarly depressed in preparations from hearts of diabetic animals. Sodium dodecylsulfate gel electrophoresis and isoelectric focusing failed to reveal differences in the patterns of contractile proteins or light subunits between diabetics and controls, but pyrophosphate gels showed a shift in the myosin pattern. Because of depressed circulating thyroid hormone levels in diabetic animals, cardiac contractile proteins were also studied in preparations from thyroidectomized rats. Calcium activities of actomyosin and myosin ATPase were lower than values found in hearts of diabetic rats. When diabetic animals were kept euthyroid with thyroid replacement, actomyosin ATPase activity was still depressed. Thus STZ diabetes causes a significant decrease in cardiac contractile protein ATPase activity. This may be related to altered proportions of myosin isoenzymes.
...
PMID:The effect of streptozotocin-induced diabetes in rats on cardiac contractile proteins. 645 19

The present study ascertained the influence of litter-size-induced perinatal nutritional modification on cardiac contractile protein enzymatic activity and isomyosin composition. Myofibrillar enzyme activities for Mg2+ -ATPase, Ca2+ -ATPase, and creatine kinase (CK) in the weanling heart were unaltered by nutritional modification. However, these enzyme activities were all significantly augmented in the adult heart. Hill plot analyses of Mg2+ -ATPase activities indicated that myofibrillar calcium regulation was not influenced by either nutritional modification or the weanling-to-adult developmental progression. Isomyosin V1 composition (90 +/- 1%) correlated with plasma thyroid hormone level in normal-growth (8/litter) weanlings. Undernutrition retarded conversion of V3 isomyosin to the V1 species while overnutrition enhanced isomyosin conversion. Isomyosin composition in weanling rats subjected to perinatal nutritional modification was independent of thyroid status. In the adult rat, plasma thyroxine levels were increased, whereas V1 isomyosin remained unchanged (88 +/- 2%) compared with that of the weanling groups. Discrepancies in the relationship between contractile protein enzymatic activities, myosin composition, and heart function are apparent between both the litter-size-adjusted weanling rats and between weanling and adult animals. These discrepancies indicate the complex relationship between heart function and contractile protein properties.
...
PMID:Perinatal nutritional modification of weanling rat heart contractile protein. 650 43


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---