I E Takács

University of Debrecen, Debrecen, Hajdu-Bihar, Hungary

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Publications (8)3.25 Total impact

  • K Nosztray, J Szabó, I E Takács, J Szegi
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    ABSTRACT: Thyroxine (T4) administered to rats in a dose of 1 mg/kg for 12 days induces cardiac hypertrophy. The purpose of the present study was to determine the effect of prophylactic + simultaneous digitoxin treatments on the development of T4-induced cardiac hypertrophy. Digitoxin (1 mg/kg body weight) was given per os, once daily for 6 days prior to T4 administration and continued simultaneously with T4 treatment. To determine myocardial enlargement, wet heart weight, myocardial nucleic acid and protein were measured. Digitoxin treatment induced a slight increase in wet ventricle weight and a significant elevation of myocardial RNA content (mg/ventricles) and concentration (mg/g). At the same time, the degree of T4-induced cardiac hypertrophy in digitoxin-treated and untreated animals was nearly the same. On the basis of these results it can be stated that--unlike the cardiac hypertrophy induced by pressure overload or hypoxia,--the T4-induced cardiac hypertrophy is not altered by digitoxin administration.
    Acta Biologica Hungarica 02/1986; 37(3-4):209-18. · 0.50 Impact Factor
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    ABSTRACT: Myocardial contractility and Ca2+-pump function of sarcoplasmic reticulum (SR) were studied on hearts of untreated, thyroidectomized and thyroxine-treated rats. In hypothyroid rats the contractile force, the maximum velocity of tension development and relaxation significantly decreased (by 73.2%, 68.2%; and 67.8%, respectively), while the time to peak tension was prolonged (by 25.9%) as compared with the control group. In hyperthyroidism opposite changes were found. Since the transport of calcium opposite changes were found. Since the transport of calcium by SR plays an important role in controlling contraction and, first of all, relaxation of muscle, function of the sarcoplasmic reticulum was also investigated under the above experimental conditions. In thyroidectomized rats the rate of Ca2+-uptake and Ca2+-activated ATPase activity of SR significantly decreased (by 31.7% and 61.0%, respectively), while Ca2+-binding remained unchanged. After thyroxine treatment both the Ca2+-uptake and binding capacity of SR were even decreased (by 25.6% and 12.9%, respectively), in spite of an increase in Ca2+-activated ATPase activity (by 67.3%). These changes in Ca2+ transport function of cardiac SR may only partially be responsible for the abnormalities in contraction and relaxation observed in hearts from hypo- and hyperthyroid rats.
    General Physiology and Biophysics 07/1985; 4(3):271-8. · 0.85 Impact Factor
  • J Szabó, K Nosztray, I E Takács, J Szegi
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    ABSTRACT: Isoproterenol (IPR) administered to rats in a dose of 5 mg/kg for 4 days induces cardiac hypertrophy. The purpose of the present study was to determine the effect of prophylactic + simultaneous digitoxin treatment on the development of IPR-induced cardiac hypertrophy. Digitoxin (1 mg/kg body weight) was given per os, once daily for 6 days prior to IPR administration and continued simultaneously with IPR treatment. To determine myocardial enlargement, wet heart weight, myocardial nucleic acid and protein were measured. Digitoxin treatment induced slight but significant increase in wet ventricle weight and myocardial RNA content (mg/ventricle). At the same time the degree of IPR-induced cardiac hypertrophy in digitoxin-treated and untreated animals was nearly the same. On the basis of these results it can be stated that--unlike the cardiac hypertrophy induced by pressure overload or hypoxia,--the IPR-induced cardiac hypertrophy is not altered by digitoxin administration.
    Acta Biologica Hungarica 02/1985; 36(3-4):305-12. · 0.50 Impact Factor
  • I E Takács, J Mészáros, J Szegi
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    ABSTRACT: The effect of hypothyroid state on the transmembrane potential was studied in isolated cardiac ventricular trabeculae of rats. Hypothyroid state was induced by methimazole treatment or thyroidectomy and checked by determining serum thyroxine level. Hypothyroidism decreased the maximum rate of depolarization (Vmax) and the resting potential, increased the overshoot and the duration of action potential at 20, 50 and 90% repolarization. These changes were more pronounced after methimazole treatment than after thyroidectomy. The results strongly suggest that in hypothyroidism the significant alterations in the voltage-time course of the transmembrane action potential influencing Ca2+-movement across the sarcolemma may have an indirect role in the decreased myocardial contractility. On the other hand, methimazole has an aspecific cardiac effect which may modify the cardiac effect of hypothyroidism induced by the drug.
    Acta Physiologica Hungarica 02/1984; 64(2):163-71. · 0.88 Impact Factor
  • J Szabó, K Nosztray, I E Takács, J Szegi
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    ABSTRACT: The purpose of the present work was to study the cardiac growth-stimulating effect of IPR in hypothyroid animals, in which the in vitro sensitivity of the myocardium to beta-adrenergic agonists is significantly decreased. To determine the degree of myocardial enlargement, wet and dry ventricle weight and myocardial RNA, DNA and protein were measured. IPR administered to euthyroid rats in a dosage of 5 mg/kg/day for 4 days induced cardiomegaly. In thyroidectomized rats, a consistent depression of IPR-induced cardiomegaly was observed. This phenomenon appears to be in accordance with earlier observations showing a marked decrease in maximal beta-receptor level of ventricular membranes after thyroidectomy or PTU treatment.
    Acta Biologica Hungarica 02/1984; 35(1):11-7. · 0.50 Impact Factor
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    ABSTRACT: Changes in contractility and ATPase activity of SR from hearts of hypothyroid rats were investigated. Rats were made hypothyroid by daily injection of 100 mg/kg methimazole for 14 days. In methimazole-treated rats, the contractile force, the maximum velocity of tension development and relaxation were significantly decreased, however, the time to peak tension remained unchanged. Function of SR was studied by determining of Ca2+-activated ATPase activity, which was significantly decreased after methimazole treatment. This diminution may be partially responsible for a slower reduction of the free Ca2+ in the surroundings of contractile proteins and thus decrease the rate of relaxation.
    Acta biologica Academiae Scientiarum Hungaricae 02/1982; 33(4):391-7.
  • I E Takács, J Szabó, K Nosztray, J Szegi
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    ABSTRACT: The purpose of the present study was to compare the ATPase activities of cardiac SR in two species in which the different intrinsic myocardial contractility can only partially be explained by the different properties of cardiac myosins. In cardiac SR isolated from rat heart, the total ATPase activity was 1512.5 +/- 23.3 nmol Pi/mg protein/min, nearly four times as high as in dog cardiac SR (408.8 +/- 28.9 nmol Pi/mg protein/min). The Ca2+-activated ATPase in rat cardiac SR represented only 23.8% of the total ATPase activity, while in dog cardiac SR it was approximately 50% of the total. Thus, the specific Ca2+-activated ATPase was nearly two times higher in the cardiac SR of the rat than in that of the dog. This higher rate of ATP hydrolysis in rat cardiac SR may be, at least in part, responsible for the increased intensity and shorter duration of the active state in the rat myocardium. Polyacrylamide gel electrophoresis of SR showed that the relative amount of Ca2+-pump protein was two times higher in dog heart, similar to the percentage of Ca2+-activated ATPase activity. At the same time, the specific Ca2+-activated ATPase activity and the relative amount of Ca2+ pump protein in both the rat and dog cardiac SR were inversely related.
    Acta biologica Academiae Scientiarum Hungaricae 02/1981; 32(1):75-81.
  • J Szabó, K Nosztray, I Takács, J Szegi
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    ABSTRACT: 1 mg/kg L-thyroxine was administered to rats for 14 days to evaluate the potential of the hyperthyroid state to induce heart hypertrophy and its effect on myosin adenosine-triphosphatase (ATPase) activity. Evidence of hyperthyroidism such as weight loss, elevation of rectal temperature, increased heart rate and oxygen consumption, was observed in all treated rats. Cardiac enlargement was determined by comparison of wet and dry ventricle weights, myocardial RNA, DNA and protein content. Wet and dry ventricle weights and the level of cardiac RNA and protein were augmented by thyroxine treatment. ATPase activity of cardiac myosin was stimulated as the Ca2+ concentration in the incubation medium increased. No difference was found in Ca2+-activation, salt sensitivity or ATPase activity of unreacted and sulphydrylmodified cardiac myosins from euthyroid or hyperthyroid groups. The results showed that in hyperthyroid rats, in contrast to some other species, the biochemical mechanism responsible for the enhancement of cardiac contractility is not an increased myosin ATPase.
    Acta physiologica Academiae Scientiarum Hungaricae 02/1979; 54(1):69-79.