Localization of cells expressing SGLT1 mRNA in the yolk sac and small intestine of broilers.

The uptake of glucose is mediated mainly by the sodium-glucose cotransporter, SGLT1. Previous studies using quantitative PCR showed that SGLT1 mRNA was induced in the yolk sac and in the small intestine prior to hatch. However, PCR analysis did not allow for the localization of cells expressing SGLT1 mRNA. The objective of this study was to use in situ hybridization to identify cells in the yolk sac and small intestine that expressed SGLT1 mRNA during the transition from late embryogenesis to early post-hatch. Expression of SGLT1 mRNA in yolk sac epithelial cells was low from embryonic d 11 to 17, peaked at embryonic d 19, and declined at day of hatch. In the small intestine, cells expressing SGLT1 mRNA were present not only along the intestinal villi but also in the crypts. There was greater expression of SGLT1 mRNA in the intestinal epithelial cells that line the villus than in the olfactomedin 4-expressing stem cells located in the crypts. The latter result suggests that stem cells have the ability to import glucose. Expression of SGLT1 mRNA in the intestine increased from embryonic d 19 to day of hatch and then maintained a high level of expression from d 1 to d 7 post-hatch. For both the yolk sac and small intestine, the temporal pattern of SGLT1 mRNA expression detected by in situ hybridization was consistent with the pattern revealed by PCR.