Kwan HY, Huang Y, Kong SK, Yao X. cGMP abolishes agonist-induced [Ca(2+)](i) oscillations in human bladder epithelial cells.
Am J Physiol Renal Physiol 2001;
281:F1067-74. [PMID:
11704557 DOI:
10.1152/ajprenal.0031.2001]
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Abstract
Cytosolic calcium oscillations may permit cells to respond to information provided by increases in intracellular Ca(2+) concentration ([Ca(2+)](i) ) while avoiding prolonged exposure to constantly elevated [Ca(2+)](i). In this study, we demonstrated that agonists could induce Ca(2+) oscillations in human bladder epithelial cells. Application of 10 microM acetylcholine or 200 nM bradykinin triggered an initial Ca(2+) transient that was followed by periodic [Ca(2+)](i) oscillations. The oscillations did not depend on extracellular Ca(2+). 8-Bromoguanosine 3',5'-cyclic monophosphate abolished acetylcholine- or bradykinin-induced oscillations. Elevation of cellular cGMP by dipyridamole, an inhibitor of cGMP-specific phosphodiesterase, also terminated the [Ca(2+)](i) oscillations. The inhibitory effect of cGMP could be reversed by KT-5823, a highly specific inhibitor of protein kinase G (PKG), suggesting that the action of cGMP was mediated by PKG. Comparison of the effect of cGMP with that of xestospongin C, an inhibitor of the inositol 1,4,5-trisphosphate (IP(3)) receptor, revealed similarities between the action of cGMP and xestospongin C. Therefore, it is likely that cGMP and PKG may target a signal transduction step(s) linked to IP(3) receptor-mediated Ca(2+) release.
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