Kinetics of D-glucose and L-leucine transport into sheep and pig intestinal brush border membrane vesicles.

The kinetic parameters (Vmax, Kt) of Na+-dependent D-glucose transport into brush border membrane vesicles (BBMV) from sheep and pig jejunum were determined. Due to the fermentation of ingested carbohydrates in the rumen the small intestine of ruminants (sheep) has to absorb much less glucose than the small intestine of monogastric omnivores (pigs) or herbivores. Kinetic analysis of the concentration dependence of D-glucose transport revealed a ten-fold smaller Vmax value combined with a five times lower Kt value in sheep BBMV compared with pig BBMV. The Vmax value for L-leucine transport did not differ between the two species investigated, whereas the Kt value in the sheep exceeded that in the pig. It is concluded from these results that the mechanism for Na+-dependent D-glucose transport in ruminants is adapted to the small amounts of carbohydrates reaching the small intestine.