Brown H M, Rydqvist B, Moser H
Department of Physiology, University of Utah School of Medicine, Salt Lake City.
Cell Calcium. 1988 Jun;9(3):105-19. doi: 10.1016/0143-4160(88)90014-0.
Intracellular Ca2+ concentration (Cai) in the dark and during light stimulation, was measured in Balanus photoreceptors with Ca2+ ion-selective electrodes (Ca-ISE) and Arsenazo III absorbance changes (AIII). The average basal Cai of 17 photoreceptors in darkness was 300 +/- 160 nM determined with liquid ion-exchanger (t-HDOPP) Ca-ISE. Ca-ISE measurements indicated that light increased Cai by 700 nM (average), whereas AIII indicated an average change of 450 nM. The time course of AIII absorbance changes matched the time course of changes in the receptor potential more closely than did the Ca-ISE. Changes in Cai were graded with light intensity but the change in Cai was much greater for a decade change in intensity at high light intensity than at low intensity. The peak light induced conductance change of voltage clamped cells had a relationship to light intensity similar to that of the change in Cai. The peak Cai level measured with Ca-ISE was in good agreement with the free Ca2+ concentration of injected buffer solutions. Control Cai levels were usually restored within 5 min following injection of Ca2+ buffers. Injection of Ca2+ buffers with free Ca2+ of 0.6 microM produced a membrane depolarization. Larger increases in Cai (greater than microM) produced by injection of CaCl2 or release of Ca2+ from injected buffers by acidifying the cell, produced a pronounced membrane hyperpolarization. Increasing Cai with all of these techniques reduced the amplitude of the receptor potential. The time course of the receptor potential recovery was usually similar to that of Cai recovery.
利用钙离子选择性电极（Ca-ISE）和偶氮胂III吸光度变化（AIII），测量了藤壶光感受器在黑暗中和光刺激期间的细胞内钙离子浓度（Cai）。用液体离子交换剂（t-HDOPP）Ca-ISE测定，17个光感受器在黑暗中的平均基础Cai为300±160 nM。Ca-ISE测量表明，光照使Cai平均增加700 nM，而AIII表明平均变化为450 nM。AIII吸光度变化的时间进程比Ca-ISE更紧密地匹配受体电位的变化时间进程。Cai的变化随光强度分级，但在高光强度下强度变化一个数量级时，Cai的变化比低光强度时大得多。电压钳制细胞的峰值光诱导电导变化与光强度的关系类似于Cai的变化。用Ca-ISE测量的峰值Cai水平与注射缓冲溶液的游离钙离子浓度高度一致。注射钙离子缓冲液后，通常在5分钟内恢复对照Cai水平。注射游离钙离子为0.6 microM的钙离子缓冲液会导致膜去极化。通过注射氯化钙或酸化细胞从注射缓冲液中释放钙离子使Cai大幅增加（大于 microM），会导致明显的膜超极化。使用所有这些技术增加Cai都会降低受体电位的幅度。受体电位恢复的时间进程通常与Cai恢复的时间进程相似。
