Increased systemic vascular resistance is responsible for blood pressure (BP) elevation in most forms of human or experimental hypertension. The enhanced contractility of structurally remodeled resistance arterioles is mediated by enhanced calcium entry (through L type voltage-dependent calcium channels - L-VDCC) and/or augmented calcium sensitization (mediated by RhoA/Rho kinase pathway). It is rather difficult to evaluate separately the role of these two pathways in BP control because BP response to the blockade of either pathway is always dependent on the concomitant activity of the complementary pathway. Moreover, vasoconstrictor systems enhance the activity of both pathways, while vasodilators attenuate them. The basal fasudil-sensitive calcium sensitization determined in rats deprived of endogenous renin-angiotensin system (RAS) and sympathetic nervous system (SNS) in which calcium entry was dose-dependently increased by L-VDCC opener BAY K8644, is smaller in spontaneously hypertensive rats (SHR) than in normotensive Wistar-Kyoto (WKY) rats. In contrast, if endogenous RAS and SNS were present in intact rats, fasudil caused a greater BP fall in SHR than WKY rats. Our in vivo experiments indicated that the endogenous pressor systems (RAS and SNS) augment calcium sensitization mediated by RhoA/Rho kinase pathway, whereas the endogenous vasodilator systems (such as nitric oxide) attenuate this pathway. However, the modulation of calcium entry and calcium sensitization by nitric oxide is strain-dependent because NO deficiency significantly augments low calcium entry in WKY and low calcium sensitization in SHR. Further in vivo and in vitro experiments should clarify the interrelationships between endogenous vasoactive systems and the contribution of calcium entry and/or calcium sensitization to BP maintenance in various forms of experimental hypertension.

• MeSH
• gating iontového kanálu MeSH
• hypertenze patofyziologie   MeSH
• krevní tlak * MeSH
• krysa rodu rattus MeSH
• modely kardiovaskulární MeSH
• potkani inbrední SHR MeSH
• renin-angiotensin systém * MeSH
• rhoA protein vázající GTP metabolismus   MeSH
• vápník metabolismus   MeSH
• vápníková signalizace * MeSH
• vápníkové kanály metabolismus   MeSH
• vazokonstrikce * MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

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 beta-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.

• MeSH
• agonisté adrenergních beta-receptorů MeSH
• AMP cyklický metabolismus   MeSH
• cévní rezistence MeSH
• draslíkové kanály řízené napětím metabolismus   MeSH
• hypertenze genetika   metabolismus   patofyziologie   MeSH
• isoprenalin MeSH
• krevní tlak MeSH
• NG-nitroargininmethylester MeSH
• potkani inbrední SHR MeSH
• potkani inbrední WKY MeSH
• synthasa oxidu dusnatého antagonisté a inhibitory   MeSH
• vápníkem aktivované draslíkové kanály s vysokou vodivostí - alfa-podjednotky metabolismus   MeSH
• vazodilatace * MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

High blood pressure (BP) of spontaneously hypertensive rats (SHR) is maintained by enhanced activity of sympathetic nervous system (SNS), whereas that of Ren-2 transgenic rats (Ren-2 TGR) by increased activity of renin-angiotensin system (RAS). However, both types of hypertension are effectively attenuated by chronic blockade of L-type voltage-dependent calcium channel (L-VDCC). The aim of our study was to evaluate whether the magnitude of BP response elicited by acute nifedipine administration is proportional to the alterations of particular vasoactive systems (SNS, RAS, NO) known to modulate L-VDCC activity. We therefore studied these relationships not only in SHR, in which mean arterial pressure was modified in a wide range of 100-210 mm Hg by chronic antihypertensive treatment (captopril or hydralazine) or its withdrawal, but also in rats with augmented RAS activity such as homozygous Ren-2 TGR, pertussis toxin-treated SHR or L-NAME-treated SHR. In all studied groups the magnitude of BP response to nifedipine was proportional to actual BP level and it closely correlated with BP changes induced by acute combined blockade of RAS and SNS. BP response to nifedipine is also closely related to the degree of relative NO deficiency. This was true for both SNS- and RAS-dependent forms of genetic hypertension, suggesting common mechanisms responsible for enhanced L-VDCC opening and/or their upregulation in hypertensive animals. In conclusions, BP response to nifedipine is proportional to the vasoconstrictor activity exerted by both SNS and RAS, indicating a key importance of these two pressor systems for actual L-VDCC opening necessary for BP maintenance.

• MeSH
• blokátory kalciových kanálů farmakologie   terapeutické užití   MeSH
• hypertenze farmakoterapie   patofyziologie   MeSH
• krevní tlak účinky léků   fyziologie   MeSH
• krysa rodu rattus MeSH
• modely nemocí na zvířatech * MeSH
• náhodné rozdělení MeSH
• nifedipin farmakologie   terapeutické užití   MeSH
• potkani inbrední SHR MeSH
• potkani inbrední WKY MeSH
• potkani transgenní MeSH
• renin-angiotensin systém účinky léků   fyziologie   MeSH
• sympatický nervový systém účinky léků   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: Calcium entry through nifedipine-sensitive L-type voltage-dependent calcium channels (L-VDCC) is augmented in spontaneously hypertensive rats (SHR) characterized by enhanced sympathetic vasoconstriction. However, the changes of calcium sensitization mediated by RhoA/Rho kinase pathway are less understood. METHODS AND RESULTS: The participation of calcium entry and calcium sensitization in the control of blood pressure (BP) and vascular contraction was studied in SHR and normotensive Wistar-Kyoto (WKY) rats. The acute administration of fasudil (Rho kinase inhibitor) caused BP decrease which lasted longer in SHR. Fasudil also attenuated adrenergic contraction in femoral or mesenteric arteries of WKY and SHR. BP reduction elicited by fasudil in WKY was more pronounced than that induced by L-VDCC blocker nifedipine (-33±2 vs. -15±3% of baseline BP, P<0.001), whereas both inhibitors were similarly effective in SHR (-36±4 vs. -41±2%). Fasudil pretreatment also attenuated BP elevation elicited by L-VDCC agonist BAY K8644 more in WKY than in SHR (-63±4 vs. -42±5%, P<0.001), indicating reduced calcium sensitization in SHR. Moreover, fasudil pretreatment shifted norepinephrine dose-response curves to the right more in WKY than in SHR. The additional nifedipine pretreatment shifted these curves further to the right but this shift was more pronounced in SHR than in WKY. Thus adrenergic vasoconstriction is more dependent on L-VDCC in SHR and on RhoA/Rho kinase pathway in WKY rats. CONCLUSION: Ca sensitization mediated by RhoA/Rho kinase pathway is attenuated in SHR compared with normotensive WKY rats. This might be a part of the compensation for enhanced Ca entry through L-VDCC in genetic hypertension.

• MeSH
• 1-(5-isochinolinsulfonyl)-2-methylpiperazin analogy a deriváty   farmakologie   MeSH
• 3-pyridinkarboxylová kyselina, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)fenyl)-, methyleste farmakologie   MeSH
• adrenergní receptory metabolismus   MeSH
• agonisté vápníkových kanálů farmakologie   MeSH
• arteriae mesentericae účinky léků   MeSH
• kinázy asociované s rho antagonisté a inhibitory   metabolismus   MeSH
• krevní tlak * MeSH
• krysa rodu rattus MeSH
• nifedipin farmakologie   MeSH
• noradrenalin farmakologie   MeSH
• oxid dusnatý metabolismus   MeSH
• potkani inbrední SHR MeSH
• potkani inbrední WKY MeSH
• rhoA protein vázající GTP metabolismus   MeSH
• teplota MeSH
• vápník metabolismus   MeSH
• vápníkové kanály - typ L metabolismus   MeSH
• vazokonstrikce účinky léků   MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Essential hypertension is a multifactorial disorder which belongs to the main risk factors responsible for renal and cardiovascular complications. This review is focused on the experimental research of neural and vascular mechanisms involved in the high blood pressure control. The attention is paid to the abnormalities in the regulation of sympathetic nervous system activity and adrenoceptor alterations as well as the changes of membrane and intracellular processes in the vascular smooth muscle cells of spontaneously hypertensive rats. These abnormalities lead to increased vascular tone arising from altered regulation of calcium influx through L-VDCC channels, which has a crucial role for excitation-contraction coupling, as well as for so-called "calcium sensitization" mediated by the RhoA/Rho-kinase pathway. Regulation of both pathways is dependent on the complex interplay of various vasodilator and vasoconstrictor stimuli. Two major antagonistic players in the regulation of blood pressure, i.e. sympathetic nervous system (by stimulation of adrenoceptors coupled to stimulatory and inhibitory G proteins) and nitric oxide (by cGMP signaling pathway), elicit their actions via the control of calcium influx through L-VDCC. However, L-type calcium current can also be regulated by the changes in membrane potential elicited by the activation of potassium channels, the impaired function of which was detected in hypertensive animals. The dominant role of enhanced calcium influx in the pathogenesis of high blood pressure of genetically hypertensive animals is confirmed not only by therapeutic efficacy of calcium antagonists but especially by the absence of hypertension in animals in which L-type calcium current was diminished by pertussis toxin-induced inactivation of inhibitory G proteins. Although there is considerable information on the complex neural and vascular alterations in rats with established hypertension, the detailed description of their appearance during the induction of hypertension is still missing.

• MeSH
• adrenergní receptory fyziologie   MeSH
• cévní endotel patofyziologie   MeSH
• guanosinmonofosfát cyklický metabolismus   MeSH
• hypertenze metabolismus   patofyziologie   MeSH
• krevní tlak fyziologie   MeSH
• lidé MeSH
• membránové potenciály MeSH
• svaly hladké cévní fyziologie   MeSH
• sympatický nervový systém patofyziologie   MeSH
• vápník metabolismus   MeSH
• vápníkové kanály - typ L metabolismus   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH

Hypertension is associated with the imbalance of vasoconstrictor and vasodilator systems. Vasodilation is usually evaluated in isolated blood vessels, but except for nitric oxide (NO), relatively little attention is given to the in vivo efficiency of particular vasodilator mechanisms. The aim of our study was to evaluate the contribution of endogenous vasodilator prostanoids, Ca(2+)-activated K(+) channels and NO to blood pressure (BP) maintenance in rats with three different forms of experimental hypertension. Both principal vasopressor systems (the renin-angiotensin system and the sympathetic nervous system) were blocked by captopril and pentolinium in conscious spontaneously hypertensive rats (SHRs), Dahl salt-hypertensive (DS-HS) rats and rats with NO-deficient hypertension, as well as in their normotensive controls. Thereafter, we monitored BP changes in rats subjected to either a sequential or an isolated blockade of prostanoid synthesis by the non-selective cyclooxygenase inhibitor, indomethacin, of Ca(2+)-activated K(+) channels by tetraethylammonium and of NO formation by N(G)-nitro-L-arginine methyl ester. All three forms of experimental hypertension were characterized by augmented sympathetic vasoconstriction. The vasodilatation exerted by endogenous prostanoids and Ca(2+)-activated K(+) channels was enhanced in all forms of hypertension, almost proportionally to BP elevation. On the contrary, NO-dependent vasodilatation was not enhanced in any form of experimental hypertension, and there was a severe relative NO deficiency in both, SHRs and DS-HS rats. In conclusion, our data suggested that there is a compensatory activation of vasodilator prostanoids and Ca(2+)-activated K(+) channels in rats with experimental hypertension, whereas NO-dependent vasodilatation is not augmented. Thus, the overall activity of vasodilator systems failed to compensate for augmented sympathetic vasoconstriction in hypertensive animals.

• MeSH
• draslíkové kanály aktivované vápníkem metabolismus   MeSH
• hypertenze etiologie   metabolismus   patofyziologie   MeSH
• indomethacin farmakologie   MeSH
• inhibitory cyklooxygenasy farmakologie   MeSH
• kaptopril farmakologie   MeSH
• krevní tlak účinky léků   fyziologie   MeSH
• krysa rodu rattus MeSH
• oxid dusnatý metabolismus   MeSH
• potkani inbrední Dahl MeSH
• potkani inbrední SHR MeSH
• prostaglandiny metabolismus   MeSH
• vazodilatace účinky léků   fyziologie   MeSH
• vazokonstrikce účinky léků   fyziologie   MeSH
• vazokonstriktory farmakologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: High blood pressure (BP) in spontaneously hypertensive rats (SHRs) is attributed to excessive activity of sympathetic nervous system (SNS) and relative nitric oxide deficiency. An important part of SNS hypertensive action is exerted by calcium influx through L-type of voltage-dependent calcium channels (L-VDCC). The overexpression of pertussis toxin (PTX)-sensitive inhibitory G-proteins (Gi) participating in the development and maintenance of high BP in SHRs suggested us to study Gi-protein involvement in the pathway through which noradrenergic vasoconstriction and calcium influx can be coupled. METHOD: The participation of main vasoactive systems (angiotensin II, norepinephrine, nitric oxide) in BP maintenance was investigated in conscious SHR and WKY rats (half of them being pretreated with PTX, 10 microg/kg i.v., 48 h before the experiment). To evaluate the contribution of Gi-proteins and L-VDCC to vasoconstriction induced by exogenous norepinephrine, dose-response curves were determined before and after acute nifedipine administration. RESULTS: PTX pretreatment of SHRs significantly decreased BP and reduced sympathetic vasoconstriction, which was partially substituted by enhanced angiotensin II-dependent vasoconstriction. PTX pretreatment also reduced nitric oxide-dependent vasodilation in both rat strains. PTX pretreatment of SHRs decreased BP component sensitive to acute blockade of calcium entry by nifedipine. In both strains, PTX pretreatment as well as acute nifedipine administration caused substantial rightward shift of norepinephrine dose-response curves (without additive effects of both treatments). CONCLUSION: The enhanced contribution of SNS to hypertension maintenance in SHRs is mediated by Gi-protein-coupled pathway controlling calcium influx through L-VDCC.

• MeSH
• hypertenze patofyziologie   MeSH
• krevní tlak účinky léků   fyziologie   MeSH
• krysa rodu rattus MeSH
• nifedipin farmakologie   MeSH
• noradrenalin farmakologie   MeSH
• pertusový toxin farmakologie   MeSH
• potkani inbrední SHR MeSH
• potkani inbrední WKY MeSH
• proteiny vázající GTP - alfa-podjednotky Gi-Go antagonisté a inhibitory   fyziologie   MeSH
• sympatický nervový systém účinky léků   patofyziologie   MeSH
• vápníková signalizace účinky léků   MeSH
• vápníkové kanály - typ L fyziologie   MeSH
• vazokonstrikce účinky léků   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• Publikační typ
• komentáře MeSH

Ischemic preconditioning (I-PC) induced by brief episodes of ischemia and reperfusion (I/R) protects the heart against sustained I/R. Although activation of mitochondrial K(ATP) channels (mitoK(ATP)) interacting with reactive oxygen species (ROS) has been proposed as a key event in this process, their role in the antiarrhythmic effect is not clear. This study was designed: 1) to investigate the involvement of mito K(ATP) opening in the effect of I-PC (1 cycle of I/R, 5 min each) on ventricular arrhythmias during test ischemia (TI, 30-min LAD coronary artery occlusion) in Langendorff-perfused rat hearts and subsequent postischemic contractile dysfunction, and 2) to characterize potential mechanisms of protection conferred by I-PC and pharmacological PC induced by mito K(ATP) opener diazoxide (DZX), with particular regards to the modulation of ROS generation. Lipid peroxidation (an indicator of increased ROS production) was determined by measurement of myocardial concentration of conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) in non-ischemic controls, non-preconditioned and preconditioned hearts exposed to TI, I-PC alone, as well as after pretreatment with DZX, mito K(ATP) blocker 5-hydroxydecanoate (5-HD) and antioxidant N-acetylcysteine (NAC). Total number of ventricular premature beats (VPB) that occurred in the control hearts (518+/-71) was significantly (P<0.05) reduced by I-PC (195+/-40), NAC (290+/-56) and DZX (168+/-22). I-PC and NAC suppressed an increase in CD and TBARS caused by ischemia indicating lower production of ROS. On the other hand, I-PC and DZX themselves moderately enhanced ROS generation, prior to TI. Bracketing of I-PC with 5-HD suppressed both, ROS production during PC and its cardioprotective effect. In conclusion, potential mechanisms of protection conferred by mito K(ATP) opening in the rat heart might involve a temporal increase in ROS production in the preconditioning phase triggering changes in the pro/antioxidant balance in the myocardium and attenuating ROS production during subsequent prolonged ischemia.

• MeSH
• acetylcystein farmakologie   MeSH
• antiarytmika farmakologie   MeSH
• antioxidancia farmakologie   MeSH
• blokátory draslíkových kanálů farmakologie   MeSH
• časové faktory MeSH
• diazoxid farmakologie   MeSH
• draslíkové kanály metabolismus   účinky léků   MeSH
• financování organizované MeSH
• funkce levé komory srdeční účinky léků   MeSH
• hydroxykyseliny farmakologie   MeSH
• ischemické přivykání MeSH
• komorové extrasystoly metabolismus   patofyziologie   prevence a kontrola   MeSH
• kontrakce myokardu účinky léků   MeSH
• krysa rodu rattus MeSH
• kyseliny dekanové farmakologie   MeSH
• látky reagující s kyselinou thiobarbiturovou metabolismus   MeSH
• obnova funkce MeSH
• oxidační stres MeSH
• perfuze MeSH
• peroxidace lipidů MeSH
• potkani Wistar MeSH
• reaktivní formy kyslíku metabolismus   MeSH
• reperfuzní poškození myokardu metabolismus   patofyziologie   prevence a kontrola   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH

High blood pressure (BP) of L-NAME hypertensive rats is maintained not only by the absence of nitric oxide (NO)- dependent vasodilatation but also by the enhancement of both sympathetic and angiotensin II-dependent vasoconstriction. The aim of the present study was to evaluate the role of inhibitory G (Gi) proteins, which are involved in tonic sympathetic vasoconstriction, in the pathogenesis of NO-deficient hypertension. We therefore studied BP response to chronic L-NAME administration (60 mg/kg/day for 4 weeks) in rats in which the in vivo inactivation of Gi proteins was induced by injection of pertussis toxin (PTX, 10 µg/kg i.v.). The impairment of sympathetic vasoconstriction due to PTX-induced Gi protein inactivation prevents the full development of NO-deficient hypertension because BP of PTX-treated rats subjected to chronic L-NAME administration did not reach hypertensive values. Nevertheless, chronic NO synthase inhibition per se is capable to increase moderately BP even in PTX-treated rats. Our data suggest that the sympathetic vasoconstriction is essential for the development of established NO-deficient hypertension.

• MeSH
• financování organizované MeSH
• hypertenze chemicky indukované   metabolismus   MeSH
• krysa rodu rattus MeSH
• modely nemocí na zvířatech MeSH
• NG-nitroargininmethylester MeSH
• pertusový toxin MeSH
• potkani Wistar MeSH
• proteiny vázající GTP - alfa-podjednotky Gi-Go antagonisté a inhibitory   metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu rattus MeSH
• mužské pohlaví MeSH
• zvířata MeSH