Ashley C C, Campbell A K
Biochim Biophys Acta. 1978 Sep 22;512(2):429-35. doi: 10.1016/0005-2736(78)90265-1.
The effect of the putative transmitter, L-glutamate, on free intracellular Ca2+, tension and membrane potential in single muscle fibres from the barnacle Balanus nubilus has been investigated. External application of L-glutamate (0.1--10 mM) resulted in a transient increase in free intracellular Ca2+, monitored by the Ca2+-activated protein aequorin. This increase in free intracellular Ca2+ was associated with membrane depolarization and force development, and was followed by a period of 'desensitization' in which the preparation was unresponsive to L-glutamate. This could be reversed by removing L-glutamate from the external saline. External application of a number of closely related compounds, including D-glutamate and L-aspartate, were ineffective for initiating the transient light response. The L-glutamate response was virtually abolished in Na-free (Li) medium and completely abolished in Ca-free (Na) medium. The responses to L-glutamate were not reduced in Mg-free medium. The fibre's response to 1mM L-glutamate was also inhibited by D-600 (10 micrometer) or by La3+ (1mM), suggesting that Ca was directly involved in the underlying ionic conductance changes brought about by this putative excitatory transmitter.
对推定递质L-谷氨酸对藤壶巴氏藤壶单根肌纤维中游离细胞内Ca2+、张力和膜电位的影响进行了研究。通过Ca2+激活蛋白水母发光蛋白监测，外部施加L-谷氨酸（0.1 - 10 mM）导致游离细胞内Ca2+短暂增加。游离细胞内Ca2+的这种增加与膜去极化和力的产生相关，随后是一段“脱敏”期，在此期间标本对L-谷氨酸无反应。通过从外部盐溶液中去除L-谷氨酸可使其逆转。外部施加多种密切相关的化合物，包括D-谷氨酸和L-天冬氨酸，均无法引发短暂的光反应。在无钠（锂）培养基中，L-谷氨酸反应几乎完全消失，在无钙（钠）培养基中则完全消失。在无镁培养基中，对L-谷氨酸的反应没有降低。纤维对1mM L-谷氨酸的反应也受到D-600（10微米）或La3+（1mM）的抑制，这表明Ca直接参与了这种推定兴奋性递质引起的潜在离子电导变化。
