THE EXPRESSION OF THE NA+ GLUCOSE COTRANSPORTER (SGLT1) GENE IN LAMB SMALL-INTESTINE DURING POSTNATAL-DEVELOPMENT

We have shown previously that the activity and abundance of the intestinal Na+/glucose cotransporter (SGLT1) declines dramatically during the postnatal development of lambs, and that it can be restored in the intestine of ruminant sheep by intra-luminal infusion Of D-glucose. The work presented in this paper has followed the expression of the SGLT1 gene along the vertical and horizontal axes of the ovine small intestine during early development, using quantitative in situ hybridisation histochemistry. Along the vertical axis, SGLT1 mRNA was first detectable just below the crypt-villus junction and rose rapidly to a peak level approx 150 mum above this point. After reaching a maximum, the amount of message gradually declined towards the villus tip. This pattern of mRNA accumulation along the crypt-villus axis was similar in all intestinal positions and age groups. Along the length of the small intestine (horizontal axis), a decline in the level of SGLT1 mRNA was observed first in the distal intestine. This decrease in SGLT1 mRNA was significant in the intestine (75% of length) of 5-week-old lambs when compared to tissue taken from 25 and 50% of length (P < 0.01 and P < 0.02, respectively). However, the observed fall in the expression of this gene during weaning did not coincide with the fall in activity and amount of SGLT1. In adult animals, where the activity of SGLT1 is very low, the amount of message was greatly reduced. This work supports the finding that the expression of SGLT1 is primarily controlled at the post-transcriptional level during the postnatal development of ovine intestine.