Christ D, Oh J, Saz H J
South Bend Center for Medical Education, Indiana University School of Medicine, Notre Dame 46556.
Parasitol Res. 1994;80(6):449-53. doi: 10.1007/BF00932689.
The effects of K+ on muscle contractility were explored in the filarial nematode Acanthocheilonema viteae (Dipetalonema viteae). The parasite was slit open longitudinally and mounted in a smooth muscle chamber that was filled with aerated (95% N2-5% CO2) physiological solution at 37 degrees C. KCl at concentrations ranging from 20 to 100 mM induced a rapid isotonic contraction of the filarial muscle. The maximal response from KCl was similar to the maximal response to acetylcholine chloride (ACh). When KCl was applied for several minutes, tolerance frequently occurred. Contractions were also induced by K2SO4 but not by NaCl, Na2SO4 or sucrose. Nifedipine was more than 10 times as potent in reducing the KCl-induced contraction as in reducing that caused by ACh. The KCl-induced contraction was abolished in a Ca-free physiological medium containing ethyleneglycol-bis-(beta-aminoethyl ether) N, N, N', N'-tetraacetic acid (EGTA, 10(-4) M). Low [Ca2+]/[Mg2+] solutions blocked the spontaneous activity, the KCl-induced contractions, and the ACh-induced contractions. KCl also induced contractions in denervated muscle strips, supporting the hypothesis that K+ acts directly on the muscle cells. These results indicate that K+ can depolarize the muscle membrane and induce a muscle contraction that is dependent on extracellular calcium ions.
在丝状线虫棘唇旋尾线虫（双瓣旋尾线虫）中研究了钾离子对肌肉收缩性的影响。将该寄生虫纵向切开并置于一个平滑肌腔室中，该腔室充满了在37℃下通有气体（95% N₂ - 5% CO₂）的生理溶液。浓度范围为20至100 mM的氯化钾可诱导丝状肌肉快速等张收缩。氯化钾的最大反应与对氯化乙酰胆碱（ACh）的最大反应相似。当应用氯化钾几分钟时，经常会出现耐受性。硫酸钾也可诱导收缩，但氯化钠、硫酸钠或蔗糖则不能。硝苯地平在降低氯化钾诱导的收缩方面的效力比降低乙酰胆碱诱导的收缩效力强10倍以上。在含有乙二醇双（β - 氨基乙基醚）N，N，N'，N' - 四乙酸（EGTA，10⁻⁴ M）的无钙生理介质中，氯化钾诱导的收缩被消除。低[Ca²⁺]/[Mg²⁺]溶液可阻断自发活动、氯化钾诱导的收缩和乙酰胆碱诱导的收缩。氯化钾也可诱导去神经肌肉条收缩，支持钾离子直接作用于肌肉细胞的假说。这些结果表明，钾离子可使肌肉膜去极化并诱导依赖于细胞外钙离子的肌肉收缩。
