Karaki H, Ahn H Y, Nakagawa H, Urakawa N
Jpn J Pharmacol. 1985 Jan;37(1):59-65. doi: 10.1254/jjp.37.59.
In Ca-deficient smooth muscle of guinea-pig taenia coli, repeated application of high-K solution (45.4 mM) containing Ca induced contractions of similar shape and magnitude. In muscle treated by a Ca- and Mg-deficient solution, however, addition of Ca and K either did not induce contraction or induced only a delayed contraction. Ouabain (1 X 10(-3) M) also inhibited Ca- and K-induced contraction. Na content of taenia coli smooth muscle increased and K content decreased during incubation in Ca- and Mg-deficient solution. Ouabain produced similar, but smaller, changes in Na and K contents. Contractility of Ca- and Mg-deficient taenia partially recovered if the muscle was treated with Na-deficient solution which resulted in a large decrease in Na content. Similar treatment produced only a small decrease in Na content in ouabain-treated taenia, and contractility did not recover in these muscles. Application of hyperosmotic NaCl (160 mM) decreased tissue weight in both control and ouabain-treated taenia. In muscle treated with Ca- and Mg-deficient solution, however, hyperosmotic NaCl application had little effect on tissue weight. Following pretreatment of muscle with Ca- and Mg-deficient solution (containing 2 mM EDTA) for 2 hr, graded contractions were induced by cumulative application of Ca between 10(-7) to 10(-6) M in the presence of Mg and ATP. It is concluded that Ca- and Mg-deficient solution increases membrane permeability and also abolishes transmembrane gradients of Na and K in guinea pig taenia coli.
在豚鼠结肠带平滑肌缺钙的情况下，反复施加含Ca的高钾溶液（45.4 mM）会引起形状和幅度相似的收缩。然而，在经缺钙和缺镁溶液处理的肌肉中，添加Ca和K要么不引起收缩，要么仅引起延迟收缩。哇巴因（1×10⁻³ M）也抑制Ca和K诱导的收缩。在缺钙和缺镁溶液中孵育期间，结肠带平滑肌的Na含量增加而K含量降低。哇巴因使Na和K含量发生类似但较小的变化。如果用缺钠溶液处理缺钙和缺镁的结肠带，其收缩力会部分恢复，这会导致Na含量大幅下降。类似的处理在哇巴因处理的结肠带中仅使Na含量略有下降，且这些肌肉的收缩力未恢复。施加高渗NaCl（160 mM）会使对照和哇巴因处理的结肠带组织重量减轻。然而，在用缺钙和缺镁溶液处理的肌肉中，施加高渗NaCl对组织重量影响很小。在用缺钙和缺镁溶液（含2 mM EDTA）对肌肉进行2小时预处理后，在Mg和ATP存在的情况下，通过累积施加10⁻⁷至10⁻⁶ M的Ca诱导分级收缩。结论是，缺钙和缺镁溶液会增加豚鼠结肠带平滑肌的膜通透性，同时消除Na和K的跨膜梯度。
