Characterization of Na+/H+ exchange in sheep rumen epithelial cells kept in primary culture

The study aimed at testing whether Na+/H+ exchange activity is maintained during isolation and cultivation of rumen epithelial cells (REC) and whether Na+/H+ exchange is altered during proliferation and differentiation. REC were isolated from sheep rumen epithelium by fractional trypsinization and further cultivated for up to 21 days. Characteristics of Na+ uptake into cultured REC were the same as previously described for the Na+/H+ exchange in the intact rumen epithelium. Na+ uptake was increased by intracellular acidification and was inhibited by high doses of amiloride. Amiloride inhibited 3H-thymidine incorporation into REC at concentrations similar to those found for the inhibition of Na+ uptake. Fetal calf serum, a growth factor, stimulated amiloride-sensitive Na+ uptake. We therefore conclude that cultured rumen epithelial cells express Na+/H+ exchange and that the activity of the exchange is at least correlated to the intensity of proliferation.