頁籤選單縮合
題 名 | Functional Coupling of Voltage-Dependent L-Type Ca[fec7]Current to Ca[fec7]-Activated K狇Current in Pituitary GH[feb0]Cells |
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作 者 | Wu,Sheng-nan; Lo,Yuk-keung; Li,Hui-fang; Shen,Ai-yu; | 書刊名 | 中國生理學雜誌 |
卷 期 | 44:4 2001.12[民90.12] |
頁 次 | 頁161-167 |
分類號 | 361.8 |
關鍵詞 | Ca[fec7]-activated K狇current; L-type Ca[fec7]current; GH[feb0]cells; |
語 文 | 英文(English) |
英文摘要 | Ca²⁺-activated K⁺ currents (I□) can contribute to action potential repolarization and after-hyperpolarization in GH3 cells. In this study, we examined how the activation of I□) at the cellular level could be functionally coupled to Ca²⁺ influx through L-type Ca²⁺ channels. A 30-msec Ca²⁺ influx step to 0 mV was found to exhibit substantial contribution of Ca²⁺ influx through the activation of I□ to the activation of I□. A bell-shaped relationship between the conditioning potentials and the integrated I□ was observed, suggesting that the magnitude of integrated I□ correlates well with that of integrated I□ in the same cell. A linear relationship of integrated I□ and integrated I□ was found with a coupling ratio of 69±7. The value of the coupling ratio was unaffected by the presence of Bay K 8644 or nimodipine, although these compounds could effectively affect the amplitudes of both I□ and I□. However, tetrandrine could decrease the coupling ratio. Paxilline or intracellular Ca²⁺ buffer with EGTA decreased the coupling ratio, while apamin had no effect on it. Interestingly, phorbol 12-myristate 13-acetate also reduced the coupling ratio significantly, whereas thapsigargin increased this value. Thus, the present study indicates that the activation of I□ during brief Ca²⁺ influx, which is inhibited by paxilline, is coupled to Ca²⁺ influx primarily through the L-type channels. The selective modulation of I□ by second messengers or Ca²⁺ release from internal stores may affect the coupling efficiency and hence cellular excitability. |
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