Lang F, Paulmichl M, Pfeilschifter J, Friedrich F, Wöll E, Waldegger S, Ritter M, Tschernko E
Institute for Physiology, University of Innsbruck, Austria.
Biochim Biophys Acta. 1991 Apr 9;1073(3):600-8. doi: 10.1016/0304-4165(91)90236-a.
Previous studies have demonstrated that bradykinin hyperpolarizes the cell membrane of subconfluent MDCK cells by increase of the potassium conductance. The present study has been performed to elucidate the intracellular mechanisms involved. To this end, the effects of bradykinin on the potential difference across the cell membrane (PD), on formation of inositol phosphates, and on intracellular calcium concentration (Cai) have been analyzed in cells without or with pretreatment with pertussis toxin or 12-O-tetradecanoylphorbol 13-acetate diester (TPA). In untreated cells, bradykinin leads to a transient increase of inositol 1,4,5-trisphosphate and inositol 1,3,4,5-tetrakisphosphate, increase of Cai, activation of potassium channels and hyperpolarization of the cell membrane. The effects of bradykinin on PD and Cai are still present in the absence of extracellular calcium. In cells pretreated with pertussis toxin the effect of bradykinin on inositol trisphosphate formation is almost abolished but bradykinin still leads to a transient increase of Cai and PD in the presence and absence of extracellular calcium. In cells pretreated with TPA the bradykinin-induced increase of inositol trisphosphate formation is blunted, the bradykinin-induced increase of Cai abolished, but the bradykinin-induced hyperpolarization still present. The observations indicate that bradykinin increases Cai in part by phorbol ester and pertussis toxin sensitive activation of phospholipase C. In addition, bradykinin is capable of enhancing Cai by utilizing pertussis toxin insensitive mechanisms. Furthermore, bradykinin is able to transiently enhance the potassium conductance without a general increase of intracellular calcium.
先前的研究表明，缓激肽可通过增加钾电导使亚汇合的MDCK细胞膜超极化。本研究旨在阐明其中涉及的细胞内机制。为此，在未用或用百日咳毒素或12 - O - 十四烷酰佛波醇13 - 乙酸酯（TPA）预处理的细胞中，分析了缓激肽对跨细胞膜电位差（PD）、肌醇磷酸形成以及细胞内钙浓度（Cai）的影响。在未处理的细胞中，缓激肽导致1,4,5 - 三磷酸肌醇和1,3,4,5 - 四磷酸肌醇短暂增加，Cai增加，钾通道激活以及细胞膜超极化。在无细胞外钙的情况下，缓激肽对PD和Cai的影响仍然存在。在用百日咳毒素预处理的细胞中，缓激肽对肌醇三磷酸形成的影响几乎被消除，但在有或无细胞外钙的情况下，缓激肽仍导致Cai和PD短暂增加。在用TPA预处理的细胞中，缓激肽诱导的肌醇三磷酸形成增加减弱，缓激肽诱导的Cai增加被消除，但缓激肽诱导的超极化仍然存在。这些观察结果表明，缓激肽部分通过佛波酯和百日咳毒素敏感的磷脂酶C激活来增加Cai。此外，缓激肽能够通过利用百日咳毒素不敏感的机制来增强Cai。此外，缓激肽能够短暂增强钾电导而不引起细胞内钙的普遍增加。
