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 maintai ned during isolation and cultivation of rumen epithelial cells (REC) a nd whether Na+/H+ exchange is altered during proliferation and differe ntiation. REC were isolated from sheep rumen epithelium by fractional trypsinization and further cultivated for up to 21 days; Characteristi cs of Na+ uptake into cultured REC were the same as previously describ ed 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 H-3 thymidine incorporation i nto REC at concentrations similar to those found for the inhibition of Na+ uptake. Fetal calf serum, a growth factor, stimulated amiloride-s ensitive Na+ uptake. We therefore conclude that cultured rumen epithel ial cells express Na+/H+ exchange and that the activity of the exchang e is at least correlated to the intensity of proliferation.