摘要：

The effect of clotrimazole on Ca 2+ signaling in Madin Darby canine kidney (MDCK) cells was investigated by using fura-2 as a Ca 2+ indicator. Clotrimazole (1–30 μM) induced a concentration-dependent [Ca 2+] i increase. The [Ca 2+] i increase comprised an initial rise and a slow decay. External Ca 2+ removal partly inhibited the Ca 2+ signals by reducing both the initial rise and the decay phase, indicating that clotrimazole triggered both Ca 2+ influx and Ca 2+ release. Pretreatment with 30 μM clotrimazole in Ca 2+-free medium abolished the Ca 2+ release induced by thapsigargin (1 μM), an endoplasmic reticulum Ca 2+ pump inhibitor, and conversely, pretreatment with thapsigargin prevented clotrimazole from releasing more Ca 2+. This suggests that the thapsigargin-sensitive Ca 2+ store is the source of clotrimazole-induced Ca 2+ release. Clotrimazole (10 μM) triggered Mn 2+ quench of fura-2 fluorescence which was partly inhibited by 1 mM La 3+. Addition of 3 mM Ca 2+ induced a [Ca 2+] i increase after preincubation with 10 μM clotrimazole in Ca 2+-free medium, indicating that clotrimazole activated capacitative Ca 2+ entry. However, 10 and 30 μM clotrimazole inhibited 1 μM thapsigargin-induced capacitative Ca 2+ entry by 21% and 74%, respectively. Pretreatment with 40 μM aristolochic acid to inhibit phospholipase A 2 reduced 30 μM clotrimazole-induced Ca 2+ release by 51%, but inhibiting phospholipase C with 2 μM U73122 had little effect. This implies that clotrimazole induces Ca 2+ release in an IP 3-independent manner, which could be modulated by phospholipase A 2-coupled events.

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