Principal vasoactive systems - renin-angiotensin system (RAS), sympathetic nervous system (SNS), nitric oxide (NO) and prostanoids - exert their vascular effects through the changes in calcium levels and/or calcium sensitization. To estimate a possible modulation of calcium sensitization by the above vasoactive systems, we studied the influence of acute and chronic blockade of particular vasoactive systems on blood pressure (BP) changes elicited in conscious normotensive rats by acute dose-dependent administration of Rho-kinase inhibitor fasudil. Adult male chronically cannulated Wistar rats were used throughout this study. The acute inhibition of NO synthase (NOS) by L-NAME enhanced BP response to fasudil, the effect being considerably augmented in rats deprived of endogenous SNS. The acute inhibition of prostanoid synthesis by indomethacin modified BP response to fasudil less than the acute NOS inhibition. The chronic NOS inhibition caused moderate BP elevation and a more pronounced augmentation of fasudilinduced BP changes compared to the effect of acute NOS inhibition. This indicates both short-term and long-term NOdependent attenuation of calcium sensitization. Long-term inhibition of RAS by captopril caused a significant attenuation of BP changes elicited by fasudil. In contrast, a long-term attenuation of SNS by chronic guanethidine treatment (in youth or adulthood) had no effect on BP response to fasudil, suggesting the absence of SNS does not affect calcium sensitization in vascular smooth muscle of normotensive rats. In conclusion, renin-angiotensin system contributes to the long-term increase of calcium sensitization and its effect is counterbalanced by nitric oxide which decreases calcium sensitization in Wistar rats., A. Brunová, M. Bencze, M. Behuliak, J. Zicha., and Obsahuje bibliografii
The slowly metabolized proteins of the extracellular matrix, typically collagen and elastin, accumulate reactive metabolites through uncontrolled non-enzymatic reactions such as glycation or the products arising from the reaction of unsaturated long chain fatty acid metabolites (possessing aldehydic groups). A typical example of these non-enzymatic changes is the formation of advanced glycation end-products (AGEs), resulting from the reaction of carbohydrates with the free amino group of proteins. The accumulation of AGEs and the resulting structural alterations cause altered tissue properties (increased stiffness, reduced elasticity) that contribute to their reduced catabolism and to their aging. Posttranslational nonenzymatic modifications of the proteins of the extracellular matrix (the formation of a typical AGE product - pentosidine) were studied in three types of tissue of three rat strains subjected to a high-fructose diet. Chronic (three-week) hyperglycemia (resulting from fructose loading) caused a significant increase in pentosidine concentration mainly in the aorta and skin of the three rat strains (Lewis, Wistar and hereditary hypertriglyceridemic rats)., K. Mikulíková, A. Eckhardt, J. Kuneš, J. Zicha, I. Mikšík., and Obsahuje bibliografii a bibliografické odkazy
Baroreflex control of heart rate was studied in inbred salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) Dahl rats that were subjected to chronic dietary sodium chloride loading (for 4 weeks) either in youth or only in adulthood, i.e. from the age of 4 or 12 weeks. Using phenylephrine administration to pentobarbital-anesthetized male rats we have demonstrated the decreased baroreflex sensitivity (lower slope for reflex bradycardia) in young prehypertensive SS/Jr rats fed a low-salt diet as compared to age-matched SR/Jr animals. High salt intake further suppressed baroreflex sensitivity in young SS/Jr but not in SR/Jr rats. Baroreflex sensitivity decreased with age in SR/Jr rats, whereas it increased in SS/Jr rats fed a low-salt diet. Thus at the age of 16 weeks baroreflex sensitivity was much higher in SS/Jr than in SR/Jr animals. High salt intake lowered baroreflex sensitivity even in adult SS/Jr rats without affecting it in adult SR/Jr rats. Nevertheless, baroreflex sensitivity was significantly lower in young SS/Jr rats with a severe salt hypertension than in adult ones with a moderate blood pressure elevation. It is concluded that the alterations of baroreflex sensitivity in young inbred SS/Jr rats (including the response to high salt intake) are similar to those described earlier for outbred salt-sensitive Dahl rats. We have, however, disclosed contrasting age-dependent changes of baroreflex sensitivity in both inbred substrains of Dahl rats., J. Nedvídek, J. Zicha., and Obsahuje bibliografii
Hereditary hypertriglyceridemic (hHTG) rats are characterized by increased blood pressure and impaired endotheliumdependent relaxation of conduit arteries. The aim of this study was to investigate the effect of long-term (4 weeks) treatment of hHTG rats with three drugs which, according to their mechanism of action, may be able to modify the endothelial function: simvastatin (an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase), spironolactone (an antagonist of aldosterone receptors) and L-arginine (a precursor of nitric oxide formation). At the end of 4th week the systolic blood pressure in the control hHTG group was 148±2 mm Hg and in control normotensive Wistar group 117±3 mm Hg. L-arginine failed to reduce blood pressure, but simvastatin (118±1 mm Hg) and spironolactone (124±4 mm Hg) treatment significantly decreased the systolic blood pressure. In isolated phenylephrine-precontracted aortic rings from hHTG rats endothelium-dependent relaxation was diminished as compared to control Wistar rats. Of the three drugs used, only simvastatin improved acetylcholine-induced relaxation of the aorta. We conclude that both simvastatin and spironolactone reduced blood pressure but only simvastatin significantly improved endothelial dysfunction of aorta. Prominent increase in the expression of eNOS in large conduit arteries may be the pathophysiological mechanism underlying the protective effect of simvastatin in hHTG rats., J. Török, I. L'upták, J. Matúšková, O. Pecháňová, J. Zicha, J. Kuneš, F. Šimko., and Obsahuje bibliografii
The incidence of metabolic syndrome increases in the developed countries, therefore biomedical research is focused on the understanding of its etiology. The study of exact mechanisms is very complicated because both genetic and environmental factors contribute to this complex disease. The ability of environmental fac tors to promote phenotype changes by epigenetic DNA modifications (i.e. DNA methylation, histone modifications) was demonstrated to play an important role in the development and predisposition to particular symptoms of metabolic syndrome. There is no doubt that the early life, such as the fetal and perinatal periods, is critical for metabolic syndrome development and therefore critical for prevention of this disease. Moreover, these changes are visible not only in individuals exposed to environmental factor s but also in the subsequent progeny for multiple generations and this phenomenon is called transgenerational inheritance. The knowledge of molecular mechanisms, by which early minor environmental stimuli modify the expression of genetic information, might be the desired key for the understanding of mechanisms leading to the change of phenotype in adulthood. This review provides a short overview of metabolic syndrome epigenetics., J. Kuneš, I. Vaněčková, B. Mikulášková, M. Behuliak, L. Maletínská, J. Zicha., and Obsahuje bibliografii
Vascular smooth muscle cells (VSMC) display considerable phenotype plasticity which can be studied in vivo on vascular remodeling which occurs during acute or chronic vascular injury. In differentiated cells, which represent contractile phenotype, there are characteristic rapid transient changes of intracellular Ca2+ concentration ([Ca2+]i), while the resting cytosolic [Ca2+]i concentration is low. It is mainly caused by two components of the Ca2+ signaling pathways: Ca2+ entry via L-type voltagedependent Ca2+ channels and dynamic involvement of intracellular stores. Proliferative VSMC phenotype is characterized by long-lasting [Ca2+]i oscillations accompanied by sustained elevation of basal [Ca2+]i. During the switch from contractile to proliferative phenotype there is a general transition from voltagedependent Ca2+ entry to voltage-independent Ca2+ entry into the cell. These changes are due to the altered gene expression which is dependent on specific transcription factors activated by various stimuli. It is an open question whether abnormal VSMC phenotype reported in rats with genetic hypertension (such as spontaneously hypertensive rats) might be partially caused by a shift from contractile to proliferative VSMC phenotype., E. Misárková, M. Behuliak, M. Bencze, J. Zicha., and Obsahuje bibliografii
A total genome scan and pharmacogenetic study were designed to search for genetic determinants of blood pressure (BP) as well as heart and kidney weights. Genome scanning was carried out in 266 F2 intercrosses from Prague hypertensive hypertriglyceridemic rats for phenotypes of organ weights, baseline BP, BP after blockade of the renin-angiotensin system (RAS) by losartan, of the sympathetic nervous system (SNS) by pentolinium, and of the nitric oxide (NO) synthase by NG-nitro-L-arginine methyl ester. Pharmacogenetic analysis showed that, in males, BP was controlled by two loci on chromosomes 1 and 5 (Chr1, Chr5) through the SNS, and these loci showed a positive contribution for relative kidney weight (KW/BW). On the other hand, baseline BP in females was controlled by two loci on Chr3 and Chr7. The effect of these loci was not mediated by the RAS, SNS or NO system. These loci did not show any effect for KW/BW. Negatively-linked loci for KW/BW and relative heart weight (HW/BW) were identified on Chr2 in both genders. Another negatively-linked locus for KW/BW, located on Chr8 in males, affected BP through the SNS. This locus on Chr8 overlapped with a previously-reported modifier locus for polycystic kidney disease (PKD). In conclusion, this pharmacogenetic study determined two loci for BP and relative organ mass implicating sympathetic overactivity. Concordance of the identified locus for KW/BW and BP through the SNS on Chr8 with the PKD locus revealed the importance of this region for renal complications in various diseases., T. Ueno, J. Tremblay, J. Kuneš, J. Zicha, Z. Dobešová, Z. Pausová, A. Y. Deng, Y. Sun, H. J. Jacob, P. Hamet., and Obsahuje bibliografii
Treatment with pertussis toxin (PTX) which eliminates the activity of Gi proteins effectively reduces blood pressure (BP) and vascular resistance in spontaneously hypertensive rats (SHR). In this study we have compared the functional characteristics of isolated arteries from SHR with and without PTX-treatment (10 μg/kg i.v., 48 h before the experiment). Rings of thoracic aorta, superior mesenteric artery and main pulmonary artery were studied under isometric conditions to measure the reactivity of these vessels to receptor agonists and to transmural electrical stimuli. We have found that the treatment of SHR with PTX had no effect on endothelium-dependent relaxation of thoracic aorta induced by acetylcholine. In PTX-treated SHR, the maximum contraction of mesenteric artery to exogenous noradrenaline was reduced and the dose-response curve to cumulative concentration of noradrenaline was shifted to the right. Similarly, a reduction in the magnitude of neurogenic contractions elicited by electrical stimulation of perivascular nerves was observed in the mesenteric artery from PTX-treated SHR. PTX treatment of SHR also abolished the potentiating effect of angiotensin II on neurogenic contractions of the main pulmonary artery. These results indicate that PTX treatment markedly diminishes the effectiveness of adrenergic stimuli in vasculature of SHR. This could importantly affect BP regulation in genetic hypertension., A. Zemančíková, J. Török, J. Zicha, J. Kuneš., and Obsahuje bibliografii a bibliografické odkazy
Spontaneously hypertensive rats (SHR) are characterized by enhanced sympathetic vasoconstriction, whereas their vasodilator mechanisms are relatively attenuated compared to their high BP. The objective of our in vivo study was to evaluate whether the impaired function of BKCa and/or KV channels is responsible for abnormal cAMP-induced vasodilatation in genetic hypertension. Using conscious SHR and normotensive WKY rats we have shown that under the basal conditions cAMP overproduction elicited by the infusion of β-adrenoceptor agonist (isoprenaline) caused a more pronounced decrease of baseline blood pressure (BP) in SHR compared to WKY rats. Isoprenaline infusion prevented BP rises induced by acute NO synthase blockade in both strains and it also completely abolished the fully developed BP response to NO synthase blockade. These cAMP-induced vasodilator effects were diminished by the inhibition of either BKCa or KV channels in SHR but simultaneous blockade of both K+ channel types was necessary in WKY rats. Under basal conditions, the vasodilator action of both K+ channels was enhanced in SHR compared to WKY rats. However, the overall contribution of K+ channels to cAMP-induced vasodilator mechanisms is insufficient in genetic hypertension since a concurrent activation of both K+ channels by cAMP overproduction is necessary for the prevention of BP rise elicited by acute NO/cGMP deficiency in SHR. This might be caused by less effective activation of these K+ channels by cAMP in SHR. In conclusion, K+ channels seem to have higher activity in SHR, but their vasodilator action cannot match sufficiently the augmented vasoconstriction in this hypertensive strain., M. Pintérová, M. Behuliak, J. Kuneš, J. Zicha., and Obsahuje bibliografii