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Title: ANG-(3-4) inhibits renal Na+-ATPase in hypertensive rats through a mechanism that involves dissociation of ANG II receptors, heterodimers, and PKA
Authors: 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)
Keywords: ANG-(3-4)
kidney proximal tubules
ouabain-resistant Na+-ATPase
spontaneously hypertensive rats
ANG II receptors
Issue Date: 1-Apr-2014
Publisher: Amer Physiological Soc
Citation: American Journal of Physiology-renal Physiology. Bethesda: Amer Physiological Soc, v. 306, n. 8, p. F855-F863, 2014.
Abstract: 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.
ISSN: 1931-857X
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