Ouabain‐sensitive ion fluxes in the smooth muscle of the guinea‐pig's taenia coli.

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Abstract
Tissues [guinea pig tenia coli] with raised intracellular Na levels, produced by incubation in K-free media, were used throughout. The uptake of 42K by these Na-loaded tissues was followed for 10 min in the presence and absence of 1.37 .times. 10-4 M ouabain, this being sufficient to inhibit Na pumping maximally. Subtraction of the uptake seen in the presence from that seen in the absence of ouabain gave estimates of the pumped ouabain-sensitive K uptake. Transmembrane ion flux was discussed. The Na pump in smooth muscle was similar to that in other tissues. It seemed to have 2 external activation sites. It was activated by external Rb, K, Cs and Li and inhibited by external Na.