THE EXPRESSION OF INTESTINAL SODIUM-GLUCOSE COTRANSPORTER IN CERVIDS

Activity and abundance of the intestinal sodium-glucose cotransporter (SGLTI) in domestic grazing ruminants (sheep. cattle) are regulated by the sugar content of the diet, If soluble nutrients bypass rumen ferm entation a substantial amount of starch will reach the small intestine . This starch, when hydrolysed, provides glucose to the luminal conten ts. The presence of SGLT1 protein in the intestinal blush border membr anes may reflect differences in feed selection and digestion sites. In order to test the bypass hypothesis we have determined the quantity o f SGLT1 protein in brush border membrane vesicles (BBMV) isolated from the intestinal tissue of ruminants of different feeding types using p olyacrylamide gel electrophoresis and western blotting with an SGLT1 a ntibody as the probe. The levels of 75 kDa SGLT1 protein were very hig h in BBMV isolated from the duodenal tissue of pre-ruminant lambs and calves and were low in the BBMV prepared from the duodenal tissues of ruminating goat, sheep and cattle. In contrast the SGLT1 protein was d etected in high abundance in the intestinal BBMV of adult cervids. Duo denal SGLT1 protein in cervids had a higher sensitivity to endogenous proteases and therefore lower stability during BBMV preparation compar ed to that of other species, but in the presence of a set of protease inhibitors a stable SGLT1 was obtained. The presence of SGLT1 protein in the intestine of cervids reflected the differences in feed selectio n of these ruminants.