二价阳离子对蛙肌纤维钾挛缩持续时间的影响。
Influence of divalent cations on potassium contracture duration in frog muscle fibres.
作者信息
Lorković H, Rüdel R
出版信息
Pflugers Arch. 1983 Jul;398(2):114-9. doi: 10.1007/BF00581057.
Single fibres or small fibre bundles were dissected from twitch muscles of frogs and washed in low Cl-solutions. Contractures were provoked by 122.5 mM K+. At room temperature (17-20 degrees C) the contracture duration was about 1.5 s in the absence of divalent cations and about 3 s in the presence of 2 mM Ca2+. Contractures were prolonged when Ca2+ was replaced by Ni2+ showing that inward Ca current was not the factor responsible for the contracture prolongation. K contracture duration was prolonged in the cold (3 degrees C) by a factor of about 4 in the presence of non-permeating divalent cations (Ni, Co), when 0.1 mM La3+ was applied together with 2 mM Ca2+, and in the virtual absence of divalent cations. The contractures were prolonged in the cold by a factor of 6 or more in the presence of permeant divalent cations (Ca, Sr, Ba, Mg, and Mn at 8 mM). Diffusion of divalent cations in the transverse tubules of the muscle fibres was shown to have a Q10 similar to that in free solution. It was concluded that inward current of divalent cations may shorten contracture duration by causing ionic depletion of the transverse tubules.
从青蛙的抽动肌中分离出单根纤维或小纤维束，并在低氯溶液中冲洗。用122.5 mM K⁺引发挛缩。在室温（17 - 20摄氏度）下，在没有二价阳离子的情况下，挛缩持续时间约为1.5秒，在存在2 mM Ca²⁺的情况下约为3秒。当Ca²⁺被Ni²⁺取代时，挛缩时间延长，这表明内向Ca电流不是导致挛缩延长的因素。在冷环境（3摄氏度）中，在存在非渗透性二价阳离子（Ni、Co）时，当0.1 mM La³⁺与2 mM Ca²⁺一起应用时，以及在几乎没有二价阳离子的情况下，K⁺挛缩持续时间延长约4倍。在存在渗透性二价阳离子（8 mM的Ca、Sr、Ba、Mg和Mn）时，冷环境中的挛缩延长6倍或更多。已证明二价阳离子在肌纤维横管中的扩散具有与在自由溶液中相似的Q10。得出的结论是，二价阳离子的内向电流可能通过导致横管离子耗竭而缩短挛缩持续时间。
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