GENETIC-REGULATION OF ENTEROCYTE FUNCTION - A QUANTITATIVE INSITU HYBRIDIZATION STUDY OF LACTASE-PHLORHIZIN HYDROLASE AND NA+-GLUCOSE COTRANSPORTER MESSENGER-RNAS IN RABBIT SMALL-INTESTINE

The enterocyte undergoes sequential changes in its structure and function as it migrates rapidly from the small intestinal crypts to the villus tip. The mechanisms by which these changes are regulated ''in tune'' with ontogenic and dietary changes in the luminal environment are currently under investigation. This study has employed oligonucleotide probes to follow the expression of the lactase-phlorizin hydrolase (LPH) and Na+-glucose cotransporter (SGLT1) genes in rabbit small intestine using quantitative in situ hybridisation histochemistry. The profiles of LPH mRNA and SGLT1 mRNA accumulation along the crypt-villus axis were found to be very similar. Although mRNA was undetectable in the crypt, LPH and SGLT1 mRNA levels rose rapidly at the crypt-villus junction, reaching a maximum between 210 mum and 330 mum above this point. Further up the villus the level of mRNAs declined. SGLT1 mRNA was present in all small intestinal segments (duodenum, jejunum and ileum), whereas LPH mRNA was absent from the ileum. LPH activity rose and fell in conjunction with mRNA, but SGLT1 activity was greatest at the villus tip where mRNA levels were considerably reduced. These data have been used to discuss the genetic regulation of enterocyte differentiation and function.