Shoback D M, Brown E M
Biochem Biophys Res Commun. 1984 Sep 17;123(2):684-90. doi: 10.1016/0006-291x(84)90283-3.
We employed the calcium (Ca++)-sensitive, intracellular dye QUIN-2 to examine the role of cytosolic Ca++ in the stimulation of PTH release by high extracellular potassium (K+) concentrations. Addition of 55 mM KC1 to cells incubated with 115 mM NaC1 and 5 mM KC1 lowered cytosolic Ca++ at either low (0.5 mM) extracellular Ca++ (from 194 +/- 14 to 159 +/- 9 nM, p less than .01, N = 6) or high (1.5 mM) extracellular calcium (from 465 +/- 38 to 293 +/- 20 nM, p less than .01, N = 10). This reduction in cytosolic Ca++ was due to high K+ per se and not to changes in tonicity since addition of 55 mM NaC1 was without effect while a similar decrease in cytosolic Ca++ occurred when cells were resuspended in 60 mM NaC1 and 60 mM KC1. PTH release was significantly (p less than .01) greater at 0.5 and 1.5 mM Ca++ in QUIN-2-loaded cells incubated with 60 mM NaC1 and 60 mM KC1 than in those exposed to 115 mM NaC1 and 5 mM KC1. In contrast to most secretory cells, therefore, stimulation of PTH release by high K+ is associated with a decrease rather than an increase in cytosolic Ca++.
我们使用对钙（Ca++）敏感的细胞内染料喹啉-2来研究细胞溶质Ca++在高细胞外钾（K+）浓度刺激甲状旁腺激素（PTH）释放中的作用。在含有115 mM氯化钠（NaCl）和5 mM氯化钾（KCl）的培养液中培养的细胞，添加55 mM KCl后，无论是在低（0.5 mM）细胞外Ca++（从194±14降至159±9 nM，p<0.01，N = 6）还是高（1.5 mM）细胞外钙（从465±38降至293±20 nM，p<0.01，N = 10）的情况下，细胞溶质Ca++均降低。细胞溶质Ca++的这种降低是由于高K+本身所致，而非由于张力变化，因为添加55 mM NaCl没有效果，而当细胞重悬于60 mM NaCl和60 mM KCl中时，细胞溶质Ca++也出现类似降低。在用60 mM NaCl和60 mM KCl培养的喹啉-2负载细胞中，在0.5和1.5 mM Ca++条件下，PTH释放显著（p<0.01）高于暴露于115 mM NaCl和5 mM KCl的细胞。因此，与大多数分泌细胞不同，高K+刺激PTH释放与细胞溶质Ca++的降低而非增加有关。
