Desensitization to ANG II in guinea pig ileum depends on membrane repolarization: role of maxi-K+ channel

Desensitization to ANG II in guinea pig ileum depends on membrane repolarization: role of maxi-K+ channel

Author Silva, Bagnolia Araujo da Autor UNIFESP Google Scholar
Nouailhetas, Viviane Louise Andree Autor UNIFESP Google Scholar
Aboulafia, Jeannine Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Desensitization of ANG II tonic contractile response of the guinea pig ileum is related to membrane repolarization determined by Ca2+-activated K+ (maxi-K+) channel opening. ANG II-stimulated depolarized myocytes presented sustained activation of maxi-K+ channels, characterized by reduction from 415 to 12 ms of the closed time constant. ANG II desensitization was prevented by 100 nM iberiotoxin, being reversible within 30 min. Depolarization by KCl, higher than 4 mM, impaired desensitization, suggesting that the membrane potential must attain a threshold to counteract the repolarization induced by maxi-K+ channel opening. Once this value is attained, there is no time dependency because the desensitization process was shut off by addition of KCl along the time course of the tonic response. In contrast, the sustained ACh tonic component was not altered by these maneuvers. We conclude that desensitization of the ANG II tonic component is foremost due to the opening of maxi-K+ channels, leading to membrane repolarization, thus dosing the voltage-dependent Ca2+ channels responsible for the Ca2+ influx that sustains the tonic component in this muscle.
Keywords isometric contraction
patch-clamp technique
acetylcholine
maxi-K+ channel
iberiotoxin
Language English
Date 1999-10-01
Published in American Journal Of Physiology-cell Physiology. Bethesda: Amer Physiological Soc, v. 277, n. 4, p. C739-C745, 1999.
ISSN 0363-6143 (Sherpa/Romeo, impact factor)
Publisher Amer Physiological Soc
Extent C739-C745
Origin http://ajpcell.physiology.org/content/277/4/C739
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000083919100017
URI http://repositorio.unifesp.br/11600/42345

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