REGULATION OF AE2 CL- HCO3- EXCHANGER DURING INTESTINAL DEVELOPMENT/

The Na+-independent Cl-/HCO3- exchangers in many tissues are encoded b y AE2, which is a member of the anion-exchanger (AE) gene family. Mole cular regulation of AE2 remains mostly unknown. In this study, AE2 mRN A levels during enterocyte differentiation and intestinal development were examined in rat small intestines. AE2 mRNA levels did not show ob vious segmental variation or vary along the crypt-villus axis. In cont rast, AE2 mRNA decreased between days 14 and 21 after birth, the perio d corresponding to the transition period between the suckling and wean ling stages in rats. Effects of L-thyroxine and dexamethasone on AE2 e xpression were examined because these hormones play important roles in gene regulation during development. L-Thyroxine administration starti ng on day 9 after birth led to an similar to 60% decrease (P < 0.001) in AE2 mRNA on day 13. Dexamethasone had no effect on AE2 mRNA level r egardless of whether the hormone was administered alone or in conjunct ion with L-thyroxine. Our results indicate that AE2 mRNA in the intest ine is regulated during development and that this regulation may in pa rt be related to hormonal changes.