Ion transporters called Na+/H+ exchangers (NHEs) play a significant role in Na+ absorption and regulation of intracellular pH and cell volume. The isoforms NHE1, NHE2, and NHE3, were identified in the intestinal epithelium. The NHE3 isoform that is localized on provides the electroneutral transcellular Na+ transport. Previous investigations showed differences in regulation of NHE3 expression during ontogenetic development and during diurnal cycle in renal tubules. However, little is known about this regulation in colon. The present study investigated, therefore, (1) the diurnal variations of colonic NHE3 mRNA transcript, (2) it's ontogenetic profile in suckling, weanling and adult rats and (3) the changes of NHE3 transcript during intestinal inflammation (TNBS-colitis) using the quantitative RT-PCR of NHE3 mRNA. We found that NHE3 mRNA level display circadian changes with higher value at the beginning of the night and this rythmicity are shifted by reverse feeding. The level of NHE3 mRNA was very high in sucklings, decreases during weaning period and partially increases again during pubescence. The level of NHE3 mRNA in adulthood was not invariable but could be up-regulated during colonic inflammation. We conclude that NHE3 is temporally regulated transporter that is controlled not only during postnatal ontogenesis but also by circadian oscilator and by the inflammatory state.

Supported by Ministry of Health grant NR 8576-3.