The effect of ouabain on ion transport across isolated sheep rumen epithelium.

1. The net flux of Na from the lumen to the blood side of isolated sheep rumen epithelium was reduced to zero in the third 30 min period after treatment with ouabain. 2. The net flux of K from blood to lumen side of the epithelium was reduced from 0-34 to 0-13 mumole/cm2. hr in the third 30 min period after ouabain treatment. 3. The net flux of Cl from lumen to blood side of the epithelium was reduced from 1-4 to 0-72 mumole/cm2. hr in the third 30 min period after ouabain treatment. 4. The results support the existence of a Cl pump independent of Na transport and also a K pump in sheep rumen epithelium.