Increased intracellular Na+ and depolarization favor angiotension tachyphylaxis in rabbit aorta

Increased intracellular Na+ and depolarization favor angiotension tachyphylaxis in rabbit aorta

Author Frediani-Neto, Eugenio Autor UNIFESP Google Scholar
Silva, Eneida de Gusmão Autor UNIFESP Google Scholar
Paiva, Therezinha Bandiera Autor UNIFESP Google Scholar
Paiva, Antonio Cechelli de Mattos Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Tachyphylaxis to both angiotensin II (ANG II) and Sar1-ANG II is observed in normal rabbit aorta rings, but helical strips show tachyphylaxis only to Sar1-ANG II, whereas everted rings are not tachyphylactic to either analogue. In normal rings, a good correlation was observed between intraluminal pH and degree of tachyphylaxis to both analogues, suggesting that rate-limiting access of the agonists to their site of action may enhance tachyphylaxis in this preparation. Membrane potential and intracellular Na+ activity measurements, as well as the relaxation by K+ of norepinephrine-contracted preparations in K+-free medium, indicated that helical strips are more depolarized than everted rings due to Na+ leakage into the smooth muscle cells. These results suggest that the differences in the degree of tachyphylaxis induced by angiotensin in different rabbit aorta preparations are due to a less accessible site of action in normal rings and to the higher intracellular Na+ and more depolarized state of helical strips relative to everted rings.
Keywords ANGIOTENSIN-II
SAR1-ANGIOTENSIN-II
TACHYPHYLAXIS
DESENSITIZATION
INTRALUMINAL PH
MEMBRANE POTENTIAL
SMOOTH MUSCLE
Language English
Date 1991-02-01
Published in American Journal Of Physiology-heart And Circulatory Physiology. Bethesda: Amer Physiological Soc, v. 260, n. 2, p. H373-H378, 1991.
ISSN 0002-9513 (Sherpa/Romeo, impact factor)
Publisher Amer Physiological Soc
Extent H373-H378
Origin http://ajpheart.physiology.org/content/260/2/H373
Access rights Closed access
Type Article
Web of Science ID WOS:A1991EY85600008
URI http://repositorio.unifesp.br/11600/42358

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