外液のCaイオン濃度変化のOpalina膜電位におよぼす影響

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1) Time changes in the membrane potential of Opalina (collected from the rectum of Rana japonica) after changing the external Ca-concentration were measured by making use of an intracellular glass capillary microelectrode and a cathode ray oscilloscope. 2) An increase in the Ca-concentration of the external medium brought about an initial rapid depolarization of the membrane followed by a slow hyperpolarization. The digree of change in membrane potential increased with the increase in Ca-concentration [see the left sides of Fig. 1 (10mMCaCl_2] and Fig. 2 (30mM CaCl_2). Also see Fig. 5, showing the relation betwwen the external Ca-concentration and the membrane potential measured three minutes after changing the CA-concetration.]. 3) The hyperpolarized membrane in a Ca-rich medium showed further repid hyperpolarization just after changing the external medium from a Ca-rich one to a normal one. Then the menbrane potential gradually decreased and reached a normal level (see the right sides of Figs. 1 and 2). The initial hyper-polarization due to the decrease in Ca-concentration became even more marked with the increase in Ca-concentration of the Ca-rich medium in which animal was adapted [compare the right side of Fig. 1(10mM CaCl_2) with the right side of Fig. 2 (30mM CaCl_2)]. 4) In a K-rich medium (KCl was substituted for all NaCl in the medium with a K-concentration of 55mM) the time course of the change in membrane potential due to the change in external Ca-concentration was almost the same as those in solutions with a normal K-concentration, although the magnitudes of the membrane potentials were extremely small (compare Figs. 3 and 4 with Figs. 1 and 2). External Na ions seem to have no direct relationship to the effect of Ca ions on membrane potential. 5) It is highly probable that the membrane of Opalina is permeable to Ca ions, and that the initial depolarization and the initial hyperpolarization are related to diffusion potentials resulting from the difference in Ca-concentration between the outside and the inside of the cell. 6) A reversal response of cilia on the cell surface of Opalina, except where a solution of CaCl_2 is locally applied (Naitoh, 1962), seem to be due to the outward mambrane current generated by the discharge of membrane potential at the membrane area depolarized by CaCl_2 solution.
社団法人日本動物学会の論文
1964-08-15

外液のCaイオン濃度変化のOpalina膜電位におよぼす影響

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