Himpens B, Lydrup M L, Hellstrand P, Casteels R
Laboratorium voor Fysiologie, Campus Gasthuisberg O/N, K.U. Leuven, Belgium.
Pflugers Arch. 1990 Dec;417(4):404-9. doi: 10.1007/BF00370660.
The free intracellular calcium ion concentration ([Ca2+]i) was measured simultaneously with isometric force in strips of guinea-pig mesotubarium using the Fura-2 technique. During the relaxed period (5-15 min) between spontaneous contractions [Ca2+]i continues to decrease after full mechanical relaxation to reach a minimal level of 86 +/- 8 nM (n = 9) just before the start of the next contraction. During the spontaneous contractions (5-15 min) [Ca2+]i reached a maximum of 211 +/- 19 nM and then oscillated between 155 +/- 16 nM and 194 +/- 9 nM. Increased extracellular Ca2+ concentration to 10 mM from the standard concentration of 1.5 mM caused a decreased frequency of spontaneous contractions and an increase in [Ca2+]i both in the relaxed and contracted states. In 10 mM extracellular Ca2+, addition of AlF4-, as 1 mM NaF + 10 microM AlCl3, caused a sustained increase in [Ca2+]i and maintained force. Addition of verapamil (10 microM) in this situation decreased [Ca2+]i to the resting level. The results suggest that the cyclic appearance of trains of action potentials is related to variation in [Ca2+]i, possibly via inactivation of Ca2(+)-dependent K+ channels.
采用Fura-2技术，在豚鼠中输卵管条带上同时测量细胞内游离钙离子浓度（[Ca2+]i）和等长收缩力。在自发收缩之间的舒张期（5 - 15分钟），[Ca2+]i在完全机械舒张后继续下降，在下一次收缩开始前达到最低水平86±8 nM（n = 9）。在自发收缩期间（5 - 15分钟），[Ca2+]i达到最大值211±19 nM，然后在155±16 nM和194±9 nM之间振荡。将细胞外Ca2+浓度从标准浓度1.5 mM增加到10 mM，导致自发收缩频率降低，并且在舒张和收缩状态下[Ca2+]i均升高。在10 mM细胞外Ca2+中，添加AlF4-（作为1 mM NaF + 10 microM AlCl3）导致[Ca2+]i持续升高并维持收缩力。在此情况下添加维拉帕米（10 microM）可使[Ca2+]i降至静息水平。结果表明，一连串动作电位的周期性出现与[Ca2+]i的变化有关，可能是通过Ca2(+)-依赖性钾通道的失活实现的。
