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- Title
Effect of calmodulin on ginseng saponin-induced Ca<sup>2+</sup>-Activated CI-channel activation in Xenopus laevis oocytes.
- Authors
Lee, Jun-Ho; Jeong, Sang-Min; Lee, Byung-Hwan; Kim, Jong-Hoon; Ko, Sung-Ryong; Kim, Seung-Hwan; Lee, Sang-Mok; Nah, Seung-Yeol
- Abstract
We previously demonstrated the ability of ginseng saponins (active ingredients of Panax ginseng) to enhance Ca2+-activated Cl∼ current. The mechanism for this ginseng saponin-induced enhancement was proposed to be the release of Ca2+ from IP3-sensitive intracellular stores through the activation of PTX-insensitive Gαa/11, proteins and PLC pathway. Recent studies have shown that calmodulin (CaM) regulates IP3 receptor-mediated Ca2+ release in both Ca2+-dependent and -independent manner. In the present study, we have investigated the effects of CaM on ginseng saponin-induced Ca2+-activated CI-current responses in Xenopus oocytes. Intraoocyte injection of CaM inhibited ginseng saponin-induced Ca2+-activated CI-current enhancement, whereas co-injection of calmidazolium, a CaM antagonist, with CaM blocked CaM action. The inhibitory effect of CaM on ginseng saponin-induced Ca2+-activated CI-current enhancement was dose- and time-dependent, with an IC50 of 14.9 ± 3.5 μM. The inhibitory effect of CaM on saponin’s activity was maximal after 6 h of intraoocyte injection of CaM, and after 48 h the activity of saponin recovered to control level. The half-recovery time was calculated to be 16.7 ± 4.3 h. Intraoocyte injection of CaM inhibited Ca2+-induced Ca2+-activated CI-current enhancement and also attenuated IP3-induced Ca2+-activated CI-current enhancement. Ca2+/CaM kinase II inhibitor did not inhibit CaM-caused attenuation of ginseng saponin-induced Ca2+-activated CI-current enhancement. These results suggest that CaM regulates ginseng saponin effect on Ca2+-activated CI-current enhancement via Ca2+-independent manner.
- Publication
Archives of Pharmacal Research, 2005, Vol 28, Issue 4, p413
- ISSN
0253-6269
- Publication type
Article
- DOI
10.1007/BF02977670