The action of ouabain on the smooth muscle cells of the guinea‐pig's taenia coli

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Abstract
The action of 10-6 g/ml of ouabain on the membrane potential, membrane activity, tension development and the ion content of the smooth muscle of the guinea-pig''s taenia coli was investigated. This ouabain concentration produced depolarization of the membrane, accompanied by an initial increase of the spike frequency and later a depolarization block. Removal of the ouabain produced a sudden and pronounced hyperpolarization leading to a block of spike discharge. Reduction of the external Na concentration or an increase of the external Ca concentration, or exposure to 10-7 g/ml epinephrine repolarized cell membrane in the presence of ouabain. Ouabain decreased the tension development of the taenia coli. Ouabain decreased the intracellular K and Cl and increased the intracellular Na concentration. However, the corresponding changes of equilibrium potentials were not sufficient to explain the changes of the membrane potential. A possible explanation for the action of ouabain is presented suggesting that the drug may decrease the Ca binding properties of the cell membrane.