Zimmermann B
Institut für Zoophysiologie und Zellbiologie, Universität Potsdam, Germany.
Cell Calcium. 1998 Jan;23(1):53-63. doi: 10.1016/s0143-4160(98)90074-4.
Ca2+ influx into secretory cells of the intact salivary gland of the blowfly Calliphora erythrocephala elicited by the agonist 5-hydroxytryptamine (5-HT) or the Ca2+ uptake inhibitor thapsigargin was studied by using Fura-2 and digital fluorescence imaging and by recordings of the transepithelial potential. Application of saturating [5-HT] in the absence of Ca2+ (Ca2+o) from the bathing saline did not affect the initial Ca2+ transient but greatly attenuated the subsequent sustained Ca2+ elevation observed in the presence of Ca2+o demonstrating that the latter component of the [Ca2+]i response is largely dependent on Ca2+ entry across the baso-lateral plasma membrane. La3+ or Gd3+ (10 microM) mimicked the effects of the withdrawal of Ca2+o. Experimental attempts temporally to uncouple 5-HT stimulation and Ca2+ influx by withdrawal of Ca2+o during agonist application revealed a second Ca2+ entry pathway. This pathway was insensitive to 10 microM La3+ and produced transient [Ca2+]i increases whose amplitudes were a function of the [5-HT] during the preceding stimulation and that were selectively suppressed by 50 microM SK&F 96365. Both (10 microM) La(3+)-insensitive [Ca2+]i transients and (10 microM) La3+ inhabitable tonic [Ca2+]i increases could be sequentially activated in the presence of 5-HT or thapsigargin (1 microM). These results indicate that Ca2+ store depletion by 5-HT or thapsigargin activates two distinct store-operated Ca2+ entry pathways, one of which supports tonic [Ca2+]i increases. The other is transiently activated, even under conditions that prohibit store refilling and does not significantly contribute to the [Ca2+]i responses evoked by saturating 5-HT concentrations.
利用Fura-2和数字荧光成像技术以及跨上皮电位记录，研究了激动剂5-羟色胺（5-HT）或Ca²⁺摄取抑制剂毒胡萝卜素引发的家蝇红头丽蝇完整唾液腺分泌细胞中的Ca²⁺内流。在无Ca²⁺（Ca²⁺ₒ）的情况下，从浴液中施加饱和浓度的[5-HT]，并不影响初始Ca²⁺瞬变，但大大减弱了在有Ca²⁺ₒ存在时观察到的随后持续的Ca²⁺升高，这表明[Ca²⁺]i反应的后一成分在很大程度上依赖于Ca²⁺通过基底外侧质膜的内流。La³⁺或Gd³⁺（10微摩尔）模拟了去除Ca²⁺ₒ的效果。在激动剂应用期间通过去除Ca²⁺ₒ来暂时解偶联5-HT刺激和Ca²⁺内流的实验尝试揭示了第二条Ca²⁺进入途径。该途径对10微摩尔La³⁺不敏感，并产生[Ca²⁺]i的瞬时增加，其幅度是先前刺激期间[5-HT]的函数，并且被50微摩尔SK&F 96365选择性抑制。在存在5-HT或毒胡萝卜素（1微摩尔）的情况下，（10微摩尔）对La³⁺不敏感的[Ca²⁺]i瞬变和（10微摩尔）对La³⁺敏感的持续性[Ca²⁺]i增加可以依次被激活。这些结果表明，5-HT或毒胡萝卜素引起的Ca²⁺储存耗竭激活了两条不同的储存操纵性Ca²⁺进入途径，其中一条支持持续性[Ca²⁺]i增加。另一条即使在禁止储存再填充的条件下也会被瞬时激活，并且对饱和5-HT浓度引起的[Ca²⁺]i反应没有显著贡献。
