Increase in Membrane Permeability in the Absence of Ca and Mg in the Smooth Muscle of Guinea-Pig Taenia Coli

• Published in: Japanese journal of pharmacology 1985, Vol.37(1), pp.59-65
• Main Authors: KARAKI, Hideaki, AHN, Hee Y., NAKAGAWA, Haruto, URAKAWA, Norimoto
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; calcium; Calcium - physiology; Cell Membrane Permeability; Colon - physiology; Fundamental and applied biological sciences. Psychology; Guinea Pigs; In Vitro Techniques; Intestine. Mesentery; Lithium - pharmacology; magnesium; Magnesium - physiology; Male; membrane permeability; Muscle Contraction - drug effects; Muscle, Smooth - physiology; Ouabain - pharmacology; Potassium - physiology; smooth muscle; Sodium - physiology; taenia coli; Time Factors; Verapamil - pharmacology; Vertebrates: digestive system
• ISSN: 0021-5198; 1347-3506
• 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 (1×10−3 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 NaCI (160 mM) decreased tissue weight in both control and ouabain-treated taenia. In muscle treated with Ca- and Mg-deficient solution, however, hyperosmotic NaCI 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.