Navegando por Palavras-chave "spontaneously hypertensive rats"

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    ANG-(3-4) inhibits renal Na+-ATPase in hypertensive rats through a mechanism that involves dissociation of ANG II receptors, heterodimers, and PKA
    (Amer Physiological Soc, 2014-04-01) Dias, Juliana; Ferrao, Fernanda M.; Axelband, Flavia; Carmona, Adriana K. [UNIFESP]; Lara, Lucienne S.; Vieyra, Adalberto; Universidade Federal do Rio de Janeiro (UFRJ); Natl Inst Sci & Technol Struct Biol & Bioimaging; Universidade Federal de São Paulo (UNIFESP)
    The physiological roles of ANG-(3-4) (Val-Tyr), a potent ANG II-derived peptide, remain largely unknown. the present study 1) investigates whether ANG-(3-4) modulates ouabain-resistant Na+-ATPase resident in proximal tubule cells and 2) verifies whether its possible action on pumping activity, considered the fine tuner of Na+ reabsorption in this nephron segment, depends on blood pressure. ANG-(3-4) inhibited Na+-ATPase activity in membranes of spontaneously hypertensive rats (SHR) at nanomolar concentrations, with no effect in Wistar-Kyoto (WKY) rats or on Na+-K+-ATPase. PD123319 (10(-7) M) and PKA((5-24)) (10(-6) M), an AT(2) receptor (AT(2)R) antagonist and a specific PKA inhibitor, respectively, abrogated this inhibition, indicating that AT(2)R and PKA are central in this pathway. Despite the lack of effect of ANG-(3-4) when assayed alone in WKY rats, the peptide (10(-8) M) completely blocked stimulation of Na+-ATPase induced by 10(-10) M ANG II in normotensive rats through a mechanism that also involves AT(2)R and PKA. Tubular membranes from WKY rats had higher levels of AT(2)R/AT(1)R heterodimers, which remain associated in 10(-10) M ANG II and dissociate to a very low dimerization state upon addition of 10(-8) M ANG-(3-4). This lower level of heterodimers was that found in SHR, and heterodimers did not dissociate when the same concentration of ANG-(3-4) was present. Oral administration of ANG-(3-4) (50 mg/kg body mass) increased urinary Na+ concentration and urinary Na+ excretion with a simultaneous decrease in systolic arterial pressure in SHR, but not in WKY rats. Thus the influence of ANG-(3-4) on Na+ transport and its hypotensive action depend on receptor association and on blood pressure.
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    Effect of treatment with cholecalciferol on the membrane potential and contractility of aortae from spontaneously hypertensive rats
    (Stockton Press, 1996-07-01) Silva, Eneida de Gusmao [UNIFESP]; Fredianineto, E.; Ferreira, A. T.; Paiva, Antonio Cechelli de Mattos[UNIFESP]; Paiva, Therezinha Bandiera [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    1 The diet of spontaneously hypertensive rats (SHR) and normotensive Wistar rats (NWR) was supplemented with 12.5 mu g cholecalciferol per 100 g body weight daily, by gavage, for 4 weeks.2 The amplitude of the contractile responses of aortic rings from SHR to potassium and adrenaline, which was smaller than in NWR aortae, was increased after treatment with cholecalciferol. No further changes were observed in the responses of NWR and SHR aortae in the presence of 100 nM apamin.3 The membrane potentials of aortae from SHR, which were higher than those of aortae from NWR, decreased after treatment with cholecalciferol. Further depolarization was observed in aortic rings from NWR, but not in aortic rings from SHR, after their preincubation with 100 nM apamin.4 It is concluded that cholecalciferol normalizes the membrane potential and contractility of aortae from SHR, probably through an effect on lipid composition and structure of the plasma membrane.
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    Impaired function of alpha-2 adrenoceptors in smooth muscle of mesenteric arteries from spontaneously hypertensive rats
    (Stockton Press, 1998-11-01) Feres, Teresa [UNIFESP]; Borges, Antonio Carlos Romao [UNIFESP]; Silva, Eneida de Gusmão [UNIFESP]; Paiva, Antonio Cechelli de Mattos [UNIFESP]; Paiva, Therezinha Bandiera [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    1 the alpha(2)-adrenoceptor function in mesenteric arteries of spontaneously hypertensive rats (SHR) was investigated by comparing membrane potential changes in response to adrenergic agonists in preparations from female SHR, Wistar-Kyoto (WKY) and normotensive Wistar rats (NWR).2 Resting membrane potential was found to be less negative in mesenteric arteries from SHR than in those from NWR and WKY. Apamin induced a decrease in the membrane potential of mesenteric artery rings without endothelium from NWR and WKY, but had no effects in those from SHR. Both UK 14,304 and adrenaline, in the presence of prazosin, induced a hyperpolarization that was significantly lower in de-endothelialized mesenteric rings from SHR than in those from NWR and WKY. in mesenteric rings with endothelium, however, similar hyperpolarization was observed in the three strains.3 in NWR mesenteric rings with endothelium the hyperpolarization induced by activation of alpha(2)-adrenoceptors was abolished by apamin, whereas in intact SHR mesenteric rings this hyperpolarization was slightly reduced by apamin and more efficiently reduced by N-omega-nitro-L-arginine.4 It is concluded that the activity of potassium channels coupled to alpha(2)-adrenoceptors is altered in the smooth muscle cells of SHR mesenteric arteries, contributing to their less negative membrane potential. On the other hand, the endothelial alpha(2)-receptors are functioning in mesenteric vessels from SHR and their stimulation induces a hyperpolarization mainly through the release of nitric oxide.
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    Inhibition of neurons in commissural nucleus of solitary tract reduces sympathetic nerve activity in SHR
    (Amer Physiological Soc, 2002-05-01) Sato, Monica A. [UNIFESP]; Colombari, Eduardo [UNIFESP]; Morrison, Shaun F.; Northwestern Univ; Universidade Federal de São Paulo (UNIFESP)
    Neurons in the commissural nucleus of the solitary tract (commNTS) play an important role in certain cardiovascular responses dependent on sympathetic vasoconstrictor activation, including the arterial chemoreceptor reflex. Electrolytic lesions of the commNTS elicit a fall in arterial pressure (AP) in spontaneously hypertensive rats (SHR). To determine whether the latter result 1) arose from elimination of commNTS neuronal activity rather than en passant axons and 2) was accompanied by a reduction in sympathetic nerve activity, we evaluated the effect of inhibition of neurons in the commNTS on basal splanchnic sympathetic nerve activity (SNA), AP, and heart rate (HR) in SHR, Wistar-Kyoto (WKY), and Sprague-Dawley (SD) rats. in chloralose-anesthetized, paralyzed, and artificially ventilated SHR, microinjection of GABA into the commNTS markedly decreased splanchnic SNA, AP, and HR. the reductions in SNA and AP following similar microinjections in WKY and SD rats were significantly less than those in SHR. Our findings suggest that tonically active neurons in the commNTS contribute to the maintenance of SNA and the hypertension in SHR. the level of tonic discharge of these commNTS neurons in normotensive WKY and SD rats may be lower than in SHR.
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    Renal hemodynamic response to erythropoietin-induced polycythemia in 5/6 nephrectomised rats is different from normal rats
    (Karger, 1998-05-01) Paixao, Ana Durce Oliveira da [UNIFESP]; Ferreira, Alice Teixeira [UNIFESP]; Oshiro, Maria Etsuko Miyamoto [UNIFESP]; Razvickas, Clara Versolato [UNIFESP]; Boim, Mirian Aparecida [UNIFESP]; Schor, Nestor [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The effects of recombinant human erythropoietin (rHuEPO)-induced polycythemia on renal function and glomerular hemodynamics were evaluated in Munich-Wistar rats (MW+EPO) before and after infusion of indomethacin; the rHuEPO effects on total renal function were also evaluated in 5/6 nephrectomized (CRF) MW and spontaneously hypertensive rats (MW-CRF+EPO and SHR-CRF+EPO, respectively). In normal MW rats, rHuEPO (300 IU/kg BW, 3 x /week, during 2 weeks) induced elevation in MAP, with maintenance of GFR, paralleled by superficial vasodilatation and elevation in SNGFR, suggesting cortical blood redistribution. These hemodynamic alterations induced by rHuEPO were blunted by indomethacin, suggesting a participation of the vasodilator prostaglandins in the renal compensatory mechanism of polycythemia. Elevation in MAP and reduction in GFR occurred in the MW+CRF+EPO group compared with the group receiving vehicle. In contrast, the SHR-CRF+EPO presented a reduction in MAP and maintenance of GFR, suggesting different rHuEPO effects depending on previous renal function and/or hypertensive state.
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    Role of anxiety levels in memory performance of spontaneously hypertensive rats
    (Lippincott Williams & Wilkins, 2004-12-01) Calzavara, M. B.; Lopez, G. B.; Abilio, V. C.; Silva, R. H.; Frussa, R.; Universidade Federal de São Paulo (UNIFESP)
    Spontaneously hypertensive rats (SHR) show behavioural differences when compared to their strain-matched controls. These differences include decreased anxiety-like behaviour in SHR, while both improved performance and behavioural deficits have been reported in learning/ memory studies. Considering that alterations in anxiety levels during the training session can modify retention performance in animal models of memory, the aim of the present study was to investigate the role of anxiety levels in the performance of SHR rats in the plus-maze discriminative avoidance task (PM-DAT), in which memory and anxiety are evaluated simultaneously. Adult (5-month-old) and young (45-day-old) SHR and normotensive Wistar rats (NWR) were treated with chlordiazepoxide (CDZ) or saline. Thirty minutes later, rats were submitted to the PM-DAT training session. After 24 h, the test session was performed. the results showed that: (1) adult SHR showed lower anxiety levels compared to adult NWR; (2) adult SHR and NWR, as well as young NWR, showed significant retention of the task, while young SHR showed impaired performance; (3) 5.0 mg/kg CDZ decreased anxiety levels in adult NWR and young and adult SHR; (4) 5.0 mg/kg CDZ impaired retention in adult SHR and NWR and increased retention in young SHR. Our data suggest an important role of anxiety levels in the performance of SHR in a plus-maze discriminative avoidance task. Behavioural Pharmacology 15:545-553 (C) 2004 Lippincott Williams Wilkins.
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    Role of ATP-sensitive potassium channels in normal and hypertension-associated pregnancy in rats
    (Blackwell Publishing, 2006-09-01) Lima, R.; Tardim, J. C. B. M.; Barros, M. E.; Boim, M. A.; Universidade Federal de São Paulo (UNIFESP)
    Activation of vascular ATP-sensitive K+ (K-ATP) channels has been implicated in vasodilator responses to pregnancy.The effect of glibenclamide, a K-ATP channel inhibitor, on systolic blood pressure (SBP) and renal function was evaluated in pregnant and non-pregnant spontaneously hypertensive rats, as well as in normotensive and hypertensive Wistar rats that had been made hypertensive by simultaneous treatment with N-G-nitro-(L)-arginine methyl ester (0.4 mg/mL) and indomethacin (2 mg/kg, i.p.) from Day 1 of gestation. Pregnant animals received 10 mg/kg glibenclamide for 12 days starting at Day 7. in addition, the mRNA levels of the vascular K-ATP channel (Kir6.2) were estimated in aorta and kidney using real-time reverse transcription-polymerase chain reaction on Day 19 of pregnancy.The decreased SBP observed in pregnant Wistar rats was paralleled by an increase in Kir6.2 mRNA levels. Glibenclamide blunted systemic vasodilation and reduced the mRNA expression of Kir6.2. There was no pregnancy induced vasodilation and no change in Kir6.2 mRNA expression in SHR. Glibenclamide had no effect on pregnant SHR. Hypertensive Wistar rats exhibited high SBP, followed by increased Kir6.2 mRNA levels. the effects of glibenclamide were not evaluated in this group because glibenclamide induced intense vaginal bleeding.The results of the present study suggest that K-ATP channels may be involved in pregnancy induced vasodilation during normotensive pregnancy, but not in pregnant SHR. Glibenclamide may have an abortive effect if administered during the early phases of gestation or in association with nitric oxide and prostaglandin inhibitors.