Blood pressure (BP) level results from the balance of vasoconstrictors (mainly sympathetic nervous system) and vasodilators (predominantly nitric oxide and endothelium-derived hyperpolarizing factor). Most of the forms of experimental hypertension are associated with sympathetic hyperactivity and endothelial dysfunction. It is evident that nitric oxide and norepinephrine are antagonists in the control of calcium influx through L-type voltage-dependent calcium channels (L-VDCC). Their effects on L-VDCC are mediated by cGMP and cAMP, respectively. Nevertheless, it remains to determine whether these cyclic nucleotides have direct effects on L-VDCC or they act through a modulation of calcium-activated K+ and Cl- channels which influence membrane potential. Rats with genetic or salt hypertension are characterized by a relative (but not absolute) NO deficiency compared to the absolute enhancement of sympathetic vasoconstriction. This dysbalance of vasoconstrictor and vasodilator systems in hypertensive animals is reflected by greater calcium influx through L-VDCC susceptible to the inhibition by nifedipine. However, when the modulatory influence of cyclic nucleotides is largely attenuated by simultaneous ganglionic blockade and NO synthase inhibition, BP of spontaneously hypertensive rats remains still elevated compared to normotensive rats due to augmented nifedipine-sensitive BP component. It remains to determine why calcium influx through L-VDCC of hypertensive rats is augmented even in the absence of modulatory influence of major vasoactive systems (sympathetic nervous system, nitric oxide)., M. Pintérová ... [et al.]., and Obsahuje seznam literatury
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
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 involv ed 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., J. Zicha ... [et al.]., and Obsahuje seznam literatury
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
Neurogenic pulmonary edema is a life-threatening complication, known for almost 100 years, but its etiopathogenesis is still not completely understood. This review summarizes current knowledge about the etiology and pathophysiology of neurogenic pulmonary edema. The roles of systemic sympathetic discharge, central nervous system trigger zones, intracranial pressure, inflammation and anesthesia in the etiopathogenesis of neurogenic pulmonary edema are considered in detail. The management of the patient and experimental models of neurogenic pulmonary edema are also discussed., J. Šedý, J. Zicha, J. Kuneš, P. Jendelová, E. Syková., and Obsahuje bibliografii a bibliografické odkazy
Neurogenic pulmonary edema (NPE), which is induced by acute spinal cord compression (SCC) unde r the mild (1.5 %) isoflurane anesthesia, is highly dependent on baroreflex-mediated bradycardia because a deeper (3 %) isoflurane anesthesia or atropine pretreatment comple tely abolished bradycardia occurrence and NPE development in rats subjected to SCC. The aim of the present study was to evaluate whether hypertension- associated impairment of baroreflex sensitivity might exert some protection against NPE developmen t in hypertensive animals. We therefore studied SCC-induced NPE development in two forms of experimental hypertension - spontaneously hypertensive rats (SHR) and salt hypertensive Dahl rats, which were reported to have reduced baroreflex sensitivity. SCC elicited NPE in both hypertensive models irrespective of their baroreflex sensitivity. It is evident that a moderate impairment of baroreflex sensitivity, which was demonstrated in salt hypertensive Dahl rats, does not exert sufficient protective effects against NPE development., J. Šedý, J. Kuneš, J. Zicha., and Obsahuje bibliografii a bibliografické odkazy
Maintenance of norepinephrine (NE)-induced contraction is dependent on Ca2+ influx through L-type voltage-dependent Ca2+ channels (VDCC), which is opposed by nitric oxide. Adrenergic receptors are coupled with different G proteins, including inhibitory G proteins (Gi) that can be inactivated by pertussis toxin (PTX). Our study was aimed to investigate the effects of endothelium removal, PTX pretreatment and acute VDCC blockade by nifedipine on the contractions of femoral arteries stimulated by norepinephrine. We used 12-week-old male WKY, half of the rats being injected with PTX (10 μg/kg i.v., 48 h before the experiment), which considerably reduced their blood pressure (BP). Contractions of isolated arteries were measured using Mulvany-Halpern myograph. NE dose-response curves determined in femoral arteries from PTX-treated WKY rats were shifted to the right compared to those from control WKY. On the contrary, removal of endothelium augmented NE dose-response curves shifting them to the left. Acute VDCC blockade by nifedipine (10-7 M) abolished all differences in NE dose-response curves which were dependent on the presence of either intact endothelium or functional Gi proteins because all NE dose-response curves were identical to the curve seen in vessels with intact endothelium from PTX-treated animals. We can conclude that BP reduction after PTX injection is accompanied by the attenuation of NE-induced contraction of femoral arteries irrespective of endothelium presence. Moreover, our data indicate that both vasodilator action of endothelium and Gi-dependent vasoconstrictor effect of norepinephrine operate via the control of Ca2+ influx through VDCC., S. Líšková, J. Kuneš, J. Zicha., and Obsahuje bibliografii a bibliografické odkazy
The objective of the current study was to search for genetic determinants associated with antihypertensive effects of angiotensin-converting enzyme (ACE) inhibitor captopril. Linkage and correlation analyses of captopril-induced effects on blood pressure (BP) with renal transc riptome were performed in the BXH/HXB recombinant inbred (RI) strains derived from spontaneously hypertensive rat (SHR) and Brown Norway (BN-Lx) progenitors. Variability of blood pressure lowering effects of captopril among RI strains was continuous suggesting a polygenic mode of inheritance. Linkage analysis of captopril- induced BP effects revealed a significant quantitative trait locus (QTL) on chromosome 15. This QTL colocalized with cis regulated expression QTL (eQTL) for the Ednrb (endothelin receptor type B) gene in the kidney (SHR allele was associated with increased renal expression) and renal expression of Ednrb correlated with captopril-induced BP effects. These results suggest that blood pressure lowering effects of ACE inhibitor captopril may be modulated by the variants at the Ednrb locus., J. Zicha ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
The development of neurogenic pulmonary edema (NPE) can be elicited by an immediate epidural balloon compression of the thoracic spinal cord. To evaluate whether a slower balloon inflation could prevent NPE development, we examined the extent of NPE in animals lesioned with a rapid (5 μl - 5 μl - 5 μl) or slow rate (3 μl - 2 μl - 2 μl - 2 μl - 2 μl - 2 μl - 2 μl) of balloon inflation. These groups were compared with the NPE model (immediate inflation to 15 μl) and with healthy controls. Slow balloon inflation prevented NPE development, whereas the pulmonary index and histology revealed a massive pulmonary edema in the group with a rapid rate of balloon inflation. Pulmonary edema was preceded by a considerable decrease in heart rate during the inflation procedure. Moreover, rapid inflation of balloon in spinal channel to either 5 μl or 10 μl did not cause NPE. Thus, a slow rate of balloon inflation in the thoracic epidural space prevents the development of neurogenic pulmonary edema, most likely due to the better adaptation of the organism to acute circulatory changes (rapid elevation of systemic blood pressure accompanied by profound heart rate reduction) during the longer balloon inflation period. It should be noted that spinal cord transection at the same level did not cause neurogenic pulmonary edema., J. Šedý ... [et al.]., and Obsahuje seznam literatury