Different pathways for Ca2+ mobilization by angiotensin II and carbachol in the circular muscle of the guinea-pig ileum

Different pathways for Ca2+ mobilization by angiotensin II and carbachol in the circular muscle of the guinea-pig ileum

Author Shimuta, S. I. Google Scholar
Borges, ACR Google Scholar
Prioste, R. N. Google Scholar
Paiva, T. B. Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Ca2+ pathways activated by angiotensin II and carbachol were evaluated in the circular muscle of the guinea-pig ileum by recording mechanical and electrical activities. Transient contractions induced by angiotensin II were greatly reduced by Ca2+ removal from the medium whereas carbachol-induced responses were not significantly altered. Nifedipine had no effect on the responses to both agonists. A high concentration of tetrodotoxin (0.1 mu M) inhibited angiotensin II-induced contractile responses without affecting the depolarization, whereas 1 mM Ni2+ inhibited the mechanical and electrical effects. Neither tetrodotoxin nor Ni2+ affected carbachol-induced effects. These results indicate that angiotensin II-induced phasic contractions depend on extracellular Ca2+ but not on voltage-dependent L-type Ca2+ channels. It is suggested that angiotensin II activates Ni2+-sensitive Na+ and non-specific cationic channels, whereas the responses to carbachol are dependent on receptor-activated Ca2+ release. Furthermore the different response of the longitudinal and circular muscles to the inhibitory effects of tetrodotoxin and Ni2+ on the angiotensin II- and carbachol-induced contractions indicates that these agonists exert their own myogenic effects on each layer and are able to trigger different Ca2+ mobilization pathways. (C) 1999 Elsevier Science B.V. All rights reserved.
Keywords angiotensin II
carbachol
ileal circular muscle
mechanical activity
electrical activity
tetrodotoxin
Ni2+
Language English
Date 1999-02-12
Published in European Journal of Pharmacology. Amsterdam: Elsevier B.V., v. 367, n. 1, p. 59-66, 1999.
ISSN 0014-2999 (Sherpa/Romeo, impact factor)
Publisher Elsevier B.V.
Extent 59-66
Origin http://dx.doi.org/10.1016/S0014-2999(98)00919-4
Access rights Closed access
Type Article
Web of Science ID WOS:000078672000009
URI http://repositorio.unifesp.br/handle/11600/26033

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