Browsing by Author "Boric, MP"

Now showing 1 - 7 of 7
  • No Thumbnail Available
    Item
    Clonidine-induced nitric oxide-dependent vasorelaxation mediated by endothelial α2-adrenoceptor activation
    (2001) Figueroa, XF; Poblete, MI; Boric, MP; Mendizábal, VE; Adler-Graschinsky, E; Huidobro-Toro, JP
    1 To assess the involvement of endothelial alpha (2)-adrenoceptors in the clonidine-induced vasodilatation, the mesenteric artery of Sprague Dawley rats was cannulated and perfused with Tyrode solution (2 ml min(-1)). We measured perfusion pressure, nitric oxide (NO) in the perfusate using chemiluminescence, and tissue cyclic GMP by RIA.
  • No Thumbnail Available
    Item
    GW1229, a novel neuropeptide Y Y-1 receptor antagonist, inhibits the vasoconstrictor effect of neuropeptide Y in the hamster microcirculation
    (1997) Bitran, M; Daniels, AJ; Boric, MP
    We studied the effect of GW1229, a novel neuropeptide Y Y-1 receptor antagonist, on the vasoconstriction induced by neuropeptide Y and structurally related analogs in the hamster cheek pouch microcirculation. Changes in arteriolar diameter and microvascular conductance were assessed by intravital microscopy and measurement of sodium(22) clearance. GW1229 did not affect basal vascular conductance but inhibited, concentration dependently, the reduction in arteriolar diameter and vascular conductance induced by 100 nM neuropeptide Y. GW1229 also counteracted the vasoconstrictor effect of 100 nM [Leu(31),Pro(34)]neuropeptide Y, and that of 300 nM neuropeptide Y-(13-36). In contrast, GW1229 had no effect on the vasoconstriction induced by noradrenaline. We conclude that the vasoconstrictor effect of neuropeptide Y in the hamster cheek pouch is mediated by neuropeptide Y Y-1 receptors. The maintenance of physiological tone in this vascular bed does not involve the participation of endogenous neuropeptide Y.
  • No Thumbnail Available
    Item
    Histamine reduces gap junctional communication of human tonsil high endothelial cells in culture
    (2004) Figueroa, XF; Alviña, K; Martínez, AD; Garcés, G; Rosemblatt, M; Boric, MP; Sáez, JC
    The regulation of gap junctional communication by histamine was studied in primary cultures of human tonsil high endothelial cells (HUTECs). We evaluated intercellular communication, levels, state of phosphorylation, and cellular distribution of gap junction protein subunits, mainly connexin (Cx)43. Histamine induced a time-dependent reduction in dye coupling (Lucifer yellow) associated with reduction in connexin43 localized at cell-cell appositions (immunofluorescence), without changes in levels and phosphorylation state of connexin43 (immunoblots). These effects were prevented with chlorpheniramine, an H-1 receptor blocker; indomethacin, a cyclooxygenase blocker; or GF109203X, a protein kinase C inhibitor. Treatment with phorbol myristate acetate, a protein kinase C activator, and 4bromo (4Br)-A23187, a calcium ionophore, mimicked the histamine-induced effects on dye coupling. 8Bromo-cAMP doubled the dye coupling extent and prevented the histamine-induced reduction in incidence of dye coupling. After 24-h histamine treatment, known to desensitize H, receptors, reapplication of histamine increased cell coupling in a way prevented by ranitidine, an H-2 receptor blocker. Thus, activation of H-1 and H-2 receptors, which increase intracellular levels of free Ca2+ and cAMP, respectively, may affect gap junctional communication in opposite ways. Stabilization of actin filaments with phalloidine diminished but did not totally prevent histamine-induced cell shape changes and reduction in dye coupling. Hence, the histamine-induced reduction in gap junctional communication between HUTEC is mediated by cytoskeleton-dependent and -independent mechanisms and might contribute to modulate endothelial function in lymphoid tissue. (C) 2004 Elsevier Inc. All fights reserved.
  • No Thumbnail Available
    Item
    Neuropeptide Y induced inhibition of noradrenaline release in rat hypothalamus
    (1999) Bitran, M; Tapia, W; Eugenín, E; Orio, P; Boric, MP
    We aimed at characterizing the receptor subtype and the signaling pathway involved in the inhibitory effect of neuropeptide Y on the release of endogenous noradrenaline from rat hypothalamus. Slices of hypothalamus were stimulated with two trains of electrical pulses, and the release of noradrenaline and nitric oxide was measured, The electrical stimulation of hypothalamic slices induced a consistent release of both endogenous noradrenaline and NO. Neuropeptide Y inhibited concentration dependently the stimulated noradrenaline release. Similarly, agonists for neuropeptide Y Y-2, Y-2 and Y-5 receptors inhibited noradrenaline release, albeit with a potency lower than neuropeptide Y. GW1229, a selective neuropeptide Y Y-1 receptor antagonist counteracted the effect of neuropeptide Y, but not that of PYY-(3-36), an agonist active at neuropeptide Y Y-5 and Y-2 receptors. These results indicate that the inhibitory effect of neuropeptide Y is likely mediated by several receptor subtypes, including neuropeptide Y Y-2, Y-5 and possibly Y-2 receptors. One mu M NPY significantly enhanced NO release induced by the electrical stimulation. N-G-monomethyl-L-arginine, an inhibitor of nitric oxide synthase, abolished NO release and blocked the inhibitory effect of neuropeptide Y on noradrenaline release. We conclude that nitric oxide participates in the signaling pathway of neuropeptide Y in the rat hypothalamus. (C) 1999 Elsevier Science B.V. All rights reserved.
  • No Thumbnail Available
    Item
    Neuropeptide Y is a vasoconstrictor and adrenergic modulator in the hamster microcirculation by acting on neuropeptide Y-1 and Y-2 receptors
    (1995) Boric, MP; Martinez, A; Donoso, MV; HuidobroToro, JP
    The microvascular effects of neuropeptide Y, and two analogs with preferential affinity for different neuropeptide Y receptor subtypes, were assessed by intravital microscopy on the hamster cheek pouch. The interaction of neuropeptide Y and its analogs with noradrenaline was also studied. Superfusion with 0.1-300 nM neuropeptide Y caused a concentration-dependent reduction in microvascular conductance that was paralleled by reductions in arteriolar and venular diameters. These effects of neuropeptide Y were equipotent with noradrenaline, but slower to develop and longer-lasting than that of noradrenaline. Neuropeptide Y did not affect permeability to macromolecules, as measured by extravasation of fluorescent dextran. The neuropeptide Y Y-1 receptor agonist, [Leu(31),Pro(34)]neuropeptide Y, mimicked neuropeptide Y with similar potency but shorter duration, while neuropeptide Y-(13-36), a neuropeptide Y Y-2 receptor agonist, was at least 10-fold less potent than neuropeptide Y to induce a delayed and prolonged reduction in microvascular conductance. The joint superfusion of 1 nM neuropeptide Y plus 0.1 mu M noradrenaline did not cause synergism, nor even summation of effects, but reduced the contractile effect of noradrenaline. No synergism was observed after a 10 min priming with 1 nM neuropeptide Y, followed by its joint application with 0.1 mu M noradrenaline, but a significant vasodilation and hyperemia ensued upon stopping noradrenaline application. Priming with 1 nM [Leu(31),Pro(34)]neuropeptide Y prolonged noradrenaline vasoconstriction without evidence of hyperemia. In contrast, priming with 1 nM neuropeptide Y-(13-36) significantly antagonized noradrenaline vasoconstriction. These findings indicate that both neuropeptide Y receptor subtypes are present in arterioles and venules of the hamster, and suggest that their activation with neuropeptide Y induces a rapid (Y-1 receptor subtype activation) and a delayed (Y-2 receptor subtype activation) vasocontractile response. The interaction with noradrenaline is complex, without evidence for synergism, but neuropeptide Y Y-2 receptor activation seems to antagonize noradrenaline and/or to facilitate auto-regulatory vasodilation after the catecholamine-induced vasoconstriction.
  • No Thumbnail Available
    Item
    Reduced natriuresis after oral sodium load in cholestatic rats
    (2000) Casar, JC; Valdivieso, A; Bravo, JA; Chacón, C; Boric, MP
    The purpose of this study was to assess the participation of the atrial natriuretic peptide (ANP)-cGMP system in electrolyte and volume handling of cholestatic rats submitted to an acute oral sodium load. Cholestasis was induced by ligation and section of the common bile duct (n = 51), Control rats were sham operated (n = 56), Three weeks after surgery, 24-hr urinary volume, sodium, potassium, cGMP and creatinine excretion were measured. Three days later, animals received 10 mmol/kg NaCl (1 M) by gavage, and urinary excretion was measured for 6 hr. In parallel groups of rats, plasma volume, electrolytes and ANP concentration, extracellular fluid volume (ECFV), and renal medullary ANP-induced cGMP production were determined in basal conditions or 1 hr after oral sodium overload. As compared with controls, cholestatic rats had a larger ECFV and higher plasma ANP (67.2 +/- 5.2 vs 39.7 +/- 3.5 pg/ml), but lower hematocrit and blood volume, and were hyponatremic, Cholestatic rats showed higher basal excretion of sodium, potassium, and volume than controls, but equal urinary cGMP, After the NaCl overload, cholestatic rats showed a reduced sodium excretion but equal urinary cGMP, One hr after sodium overload, both groups showed hypernatremia, but whereas in control rats ECFV and ANP increased (50.7 +/- 4.7 pg/ml), in cholestatic rats ECFV was unchanged, and plasma volume and ANP were reduced (37.5 +/- 5.8 pg/ml), ANP-induced cGMP production in renal medulla was similar in cholestatic and control nonloaded rats (14.2 +/- 5.2 vs 13.4 +/- 2.6 fmol/min/mg), One hr after the load, medullary cGMP production rose significantly in both groups, without difference between them (20.6 +/- 3.1 vs 22.7 +/- 1.7 fmol/min/mg). We conclude that the blunted excretion of an acute oral sodium load in cholestatic rats is associated with lower plasma ANP due to differences in body fluid distribution and cannot be explained by renal refractoriness to ANP.
  • No Thumbnail Available
    Item
    Stimulation of NO production and of eNOS phosphorylation in the microcirculation in vivo
    (2000) Durán, WN; Seyama, A; Yoshimura, K; González, DR; Jara, PI; Figueroa, XF; Boric, MP
    The role of nitric oxide (NO) in microvascular permeability is controversial, in part because the regulation of its endothelial constitutive synthase, eNOS, has been studied in vitro but not in vivo. Our study was designed to detect the morphologic and functional presence of eNOS and to test whether eNOS could be phosphorylated by platelet-activating factor (PAF), an agent that induces hyperpermeability. Immunocytochemistry was applied using human anti-eNOS antibodies in the hamster cheek pouch (hcp). The hcp microvessels demonstrated positive reaction products in the endothelium. The functional presence of eNOS in hcp was investigated by topical application of 10(-7) M PAF to the hcp and by measuring NO production by chemiluminescence. The mean baseline value of NO release was 63.3 +/- 6.9 pmol/ml (mean +/- SE), Application of PAF led to an increase in mean NO release to 120.8 +/- 31.2 pmol/ml (P < 0.05). In another series of experiments, 10(-7) M PAF was applied topically to hcp preincubated with [P-32]orthophosphoric acid. Immunoprecipitation and Western blots detected P-32-labeled bands that migrated with the mobility of positive eNOS indicating phosphorylated eNOS protein. The intensity of the radioactive bands was evaluated by computer;assisted image analysis. Comparison of the net band intensities yielded a mean PAF-treated/control ratio of 1.6 +/- 0.1. Our data demonstrate the morphologic and functional presence of eNOS in the microcirculation. The data also provide evidence that the function of microvascular eNOS is subject to regulation by phosphorylation. (C) 2000 Academic Press.