TY - JOUR
T1 - Inhibitory actions by ibandronate sodium, a nitrogen-containing bisphosphonate, on calcium-activated potassium channels in Madin-Darby canine kidney cells
AU - Wu, Sheng Nan
AU - Chen, Hui Zhen
AU - Chou, Yu Hung
AU - Huang, Yan Ming
AU - Lo, Yi Ching
N1 - Funding Information:
The authors would like to thank Yu-Kai Liao and Ching-An Kao for contributing to part of the earlier experiments. This study was partly supported by National Cheng Kung University (no. 1030101 ), Tainan City, Taiwan. Hui-Zen Chen received a student fellowship from National Cheng Kung University, Tainan City, Taiwan.
Publisher Copyright:
© 2015 Published by Elsevier Ireland Ltd.
PY - 2015/8/1
Y1 - 2015/8/1
N2 - The nitrogen-containing bisphosphonates used for management of the patients with osteoporosis were reported to influence the function of renal tubular cells. However, how nitrogen-containing bisphosphates exert any effects on ion currents remains controversial. The effects of ibandronate (Iban), a nitrogen-containing bisphosphonate, on ionic channels, including two types of Ca2+-activated K+ (KCa) channels, namely, large-conductance KCa (BKCa) and intermediate-conductance KCa (IKCa) channels, were investigated in Madin-Darby canine kidney (MDCK) cells. In whole-cell current recordings, Iban suppressed the amplitude of voltage-gated K+ current elicited by long ramp pulse. Addition of Iban caused a reduction of BKCa channels accompanied by a right shift in the activation curve of BKCa channels, despite no change in single-channel conductance. Ca2+ sensitivity of these channels was modified in the presence of this compound however, the magnitude of Iban-mediated decrease in BKCa-channel activity under membrane stretch with different negative pressure remained unchanged. Iban suppressed the probability of BKCa-channel openings linked primarily to a shortening in the slow component of mean open time in these channels. The dissociation constant needed for Iban-mediated suppression of mean open time in MDCK cells was 12.2μM. Additionally, cell exposure to Iban suppressed the activity of IKCa channels, and DC-EBIO or 9-phenanthrol effectively reversed its suppression. Under current-clamp configuration, Iban depolarized the cells and DC-EBIO or PF573228 reversed its depolarizing effect. Taken together, the inhibitory action of Iban on KCa-channel activity may contribute to the underlying mechanism of pharmacological or toxicological actions of Iban and its structurally similar bisphosphonates on renal tubular cells occurring in vivo.
AB - The nitrogen-containing bisphosphonates used for management of the patients with osteoporosis were reported to influence the function of renal tubular cells. However, how nitrogen-containing bisphosphates exert any effects on ion currents remains controversial. The effects of ibandronate (Iban), a nitrogen-containing bisphosphonate, on ionic channels, including two types of Ca2+-activated K+ (KCa) channels, namely, large-conductance KCa (BKCa) and intermediate-conductance KCa (IKCa) channels, were investigated in Madin-Darby canine kidney (MDCK) cells. In whole-cell current recordings, Iban suppressed the amplitude of voltage-gated K+ current elicited by long ramp pulse. Addition of Iban caused a reduction of BKCa channels accompanied by a right shift in the activation curve of BKCa channels, despite no change in single-channel conductance. Ca2+ sensitivity of these channels was modified in the presence of this compound however, the magnitude of Iban-mediated decrease in BKCa-channel activity under membrane stretch with different negative pressure remained unchanged. Iban suppressed the probability of BKCa-channel openings linked primarily to a shortening in the slow component of mean open time in these channels. The dissociation constant needed for Iban-mediated suppression of mean open time in MDCK cells was 12.2μM. Additionally, cell exposure to Iban suppressed the activity of IKCa channels, and DC-EBIO or 9-phenanthrol effectively reversed its suppression. Under current-clamp configuration, Iban depolarized the cells and DC-EBIO or PF573228 reversed its depolarizing effect. Taken together, the inhibitory action of Iban on KCa-channel activity may contribute to the underlying mechanism of pharmacological or toxicological actions of Iban and its structurally similar bisphosphonates on renal tubular cells occurring in vivo.
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U2 - 10.1016/j.toxrep.2015.08.010
DO - 10.1016/j.toxrep.2015.08.010
M3 - Article
AN - SCOPUS:84940533564
SN - 2214-7500
VL - 2
SP - 1182
EP - 1193
JO - Toxicology Reports
JF - Toxicology Reports
ER -