The aim of this study was to assess the molecular basis of renal Na,K-ATPase disturbances in response to NO-deficient hypertension induced in rats by NO-synthase inhibition with 40 mg/kg/day NG-nitro-L-arginine methyl ester (L-NAME) for four weeks. After 4-week administration of L-NAME, the systolic blood pressure (SBP) increased by 30 %. Three weeks after terminating the treatment, SBP recovered to control value. When activating the Na,K-ATPase with its substrate ATP, a 36 % increase in Km and 29 % decrease in Vmax values were observed in NO-deficient rats. During activation with Na+, the Vmax was decreased by 20 % and the KNa was increased by 111 %, indicating a profound decrease in the affinity of the Na+-binding site in NO-deficient rats. After spontaneous recovery from hypertension, the Vmax remained at the level as in hypertension for both types of enzyme activation. However, in the presence of lower concentrations of substrate which are of physiological relevance an improvement of the enzyme activity was observed as documented by return of Km for ATP to control value. The KNa value for Na+ was decreased by 27 % as compared to hypertension, but still exceeded the corresponding value in the control group by 55 % thus resulting in a partial restoration of Na+ affinity of Na,K-ATPase which was depressed as a consequence of NO-dependent hypertension., N. Vrbjar, V. Javorková, O. Pecháňová., and Obsahuje bibliografii
The aim of the present study was to determine the effect of angiotensin-converting enzyme inhibitor captopril on cGMP and cAMP concentration in the left ventricle and aorta after NO synthase inhibition by 4-week-lasting NG-nitro-L-arginine-methyl ester (L-NAME) treatment. Five groups of rats were investigated: controls, L-NAME in the dose 20 mg/kg/day (L-NAME 20), L-NAME in the dose 40 mg/kg/day (L-NAME 40), captopril in the dose 100 mg/kg/day, L-NAME 40 mg/kg/day together with captopril 100 mg/kg/day. Captopril completely prevented L-NAME-induced hypertension and LV hypertrophy development. Compared to the controls, cGMP concentration in the L-NAME 20 and L-NAME 40 groups was decreased by 13 % and 22 %, respectively, in the left ventricle and by 27 % and 56 % in the aorta, respectively. Captopril did not influence this decrease of cGMP concentration. Cyclic AMP concentration in the aorta of L-NAME 20 group increased by 17 %. In the L-NAME 40 group, cAMP concentration increased by 17 % in the left ventricle and by 34 % in the aorta compared to controls. This increase was enhanced in rats given L-NAME together with captopril. Captopril alone had no effect on cAMP concentration. We conclude that captopril does not affect the concentration of cGMP, however, it has more than the additive effect on the cAMP concentration increase in the cardiovascular system during long-term NO synthase inhibition., O. Pecháňová, I. Bernátová., and Obsahuje bibliografii
The nitric oxide/cGMP system has been shown to play a crucial role in the mechanism of learning and memory. The aim of the present study was to investigate whether the inhibition of NO synthase in brain regions leads to alterations of spontaneous behavior in rats. Male Wistar rats were treated with NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) at the dose of 40 mg/kg/day. After 4 weeks of L-NAME treatment, NO synthase activity was significantly decreased by 75 % in the cerebellum, by 71 % in the cerebral cortex and by 72 % in the thoracic spinal cord. Decreased NO synthase activity in the nervous tissue was associated with decreased motor horizontal and vertical activities as well as by lowered frequency of sniffing, cleaning and defecation. It is concluded that the inhibition of NO synthase activity has a suppressive effect on spontaneous behavior of rats., L. Halčák, O. Pecháňová, Z. Žigová, L. Klemová, M. Novacký, I. Bernátová., and Obsahuje bibliografii
NG-nitro-D-arginine-methyl ester (D-NAME) is considered to be an inactive enantiomer of L-NAME and is generally used as the negative control for NO synthase inhibition with L-NAME. With the aim to compare the effects of 4-week L-NAME and D-NAME treatments on hemodynamic and cardiovascular structural parameters, four groups of male Wistar rats were investigated: the controls and groups administered 40 and 20 mg/kg/day of L-NAME and 40 mg/kg/day of D-NAME. At the end of the experiment, myocardial NO synthase activity decreased by 42, 24 and 25 %; aortic NO synthase activity decreased by 35, 15 and 13 % vs. controls in the L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. The DNA concentrations in the myocardium and the aorta increased significantly after L-NAME and D-NAME treatments. The inhibition of NO synthase was accompanied by a significant elevation in systolic blood pressure in all three groups. The LVW/BW ratio increased by 27, 14 and 13 % vs. controls in the L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. The aortic wall mass, measured as the crossectional area, increased by 45, 17 and 25 % vs. controls in the L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. Myocardial fibrosis represented 0.94 % in the controls, but 7.96, 4.70 and 5.25 % in L-NAME 40, L-NAME 20 and D-NAME 40 groups, respectively. It is concluded that D-NAME, although less affective than L-NAME, inhibits NO synthase activity resulting in hemodynamic and structural changes in the cardiovascular system similar to the changes induced by half the dose of L-NAME. Thus, the consideration of D-NAME as an inactive enantiomer and its use as the negative control needs to be reevaluated., P. Babál, O. Pecháňová, I. Bernátová., and Obsahuje bibliografii
It was previously shown that 4 hours´ lasting inhibition of nitric oxide synthesis by administration of an L-arginine analogue, the NG-nitro-L-arginine methyl ester (L-NAME) changed the affinity of the Na-binding site of Na,K-ATPase thus resulting in elevation of enzyme activity especially at higher concentrations of sodium. Using the same experimental model, we focused our attention in the present study to the question of binding of ATP to the enzyme molecule in the left ventricle (LV), ventricular septum (S) and the right ventricle (RV) of the dog heart. Activation of the enzyme by increasing concentrations of ATP revealed a significant increase of the Vmax only in septum (by 38 %). The KM increased significantly in septum (by 40 %) and in left ventricle (by 56 %) indicating an altered sensitivity of the ATP-binding site of Na,K-ATPase in the hearts of NO-deficient animals. The alterations of Na,K-ATPase in its ability to bind and hydrolyze ATP are localized to the tissue surrounding the cavity of the left ventricle., N. Vrbjar, M. Strnisková, O. Pecháňová, M. Gerová., and Obsahuje bibliografii
It is known that hypertension is accompanied by increased [Na+]i. The functional properties of Na,K-ATPase, which transports the Na+ out and K+ into myocardial cells during the relaxation phase, were investigated in the left ventricle (LV), septum (SV) and the right ventricle (RV) of anesthetized dogs with moderate acute blood pressure elevation elicited by short-term (4-hour) NO synthase inhibition. The NO-insufficiency was induced by administration of an L-arginine analogue, the NG-nitro-L-arginine methyl ester (L-NAME). Concerning the function of Na,K-ATPase under the conditions of lowered NO synthesis, we focused our attention to the binding of Na+ to the enzyme molecule. Activation of the enzyme by increasing Na+ concentrations revealed significant changes in both the maximal velocity (Vmax) and the affinity for Na+ (KNa) in all investigated heart sections. The Vmax increased by 27 % in LV, by 87 % in SV and by 58 % in RV. The KNa value increased by 86 % in LV, by 105 % in SV and by 93% in RV, indicating an apparent decrease in the sensitivity of the Na+-binding site in the Na,K-ATPase molecule. This apparently decreased pump affinity for Na+ together with the increase of Vmax suggest that, during the short-term inhibition of NO synthesis, the Na,K-ATPase is capable of extruding the excessive Na+ from the myocardial cells more effectively at higher [Na+]i as compared to the Na,K-ATPase of control animals., N. Vrbjar, M. Strnisková, O. Pecháňová, M. Gerová., and Obsahuje bibliografii
Aldosterone receptor antagonist, spironolactone, has been shown to prevent remodeling of the heart in several models of left ventricular hypertrophy. The aim of the present study was to determine whether the treatment with spironolactone can prevent hypertension, reduction of tissue nitric oxide synthase activity and left ventricular (LV) and aortic remodeling in NG-nitro-L-arginine methyl ester (L-NAME)-induced hypertension. Four groups of rats were investigated: control, spironolactone (200 mg/kg), L-NAME (40 mg/kg) and L-NAME + spironolactone (in corresponding dosage). Animals were studied after 5 weeks of treatment. The decrease of NO-synthase activity in the LV and kidney was associated with the development of hypertension and LV hypertrophy, with increased DNA concentration in the LV, and remodeling of the aorta in the L-NAME group. Spironolactone prevented the inhibition of NO-synthase activity in the LV and kidney and partially attenuated hypertension and LVH development and the increase in DNA concentration. However, remodeling of the aorta was not prevented by spironolactone treatment. We conclude that the aldosterone receptor antagonist spironolactone improved nitric oxide production and partially prevented hypertension and LVH development without preventing hypertrophy of the aorta in NO-deficient hypertension. The reactive growth of the heart and aorta seems to be controlled by different mechanisms in L-NAMEinduced hypertension., F. Šimko, J. Matúšková, I. L'upták, T. Pinčíková, K. Krajčírovičová, S. Štvrtina, J. Pomšár, V. Pelouch, L'. Paulis, O. Pecháňová., and Obsahuje bibliografii