A Possible Role of a Nuclear Factor NF-LPH1 in the Regional Expression of Lactase-Phlorizin Hydrolase along the Small Intestine

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Lactase-phlorizin hydrolase (LPH), an enterocyte-specific disaccharidase, displays not only a post weaning decline but also regional differences in the small intestine. To investigate the mechanisms of regional LPH expression along the small intestine, the correlation between LPH mRNA abundance, lactase activity and the amount of a nuclear factor (NF-LPH 1) binding to a cis-element was determined in various intestinal segments of suckling and adult rats. In suckling rats, both LPH mRNA and lactase activity were expressed at maximum in the jejunum, but they were hardly detected in the colon. In adult rats, both LPH mRNA and lactase activity were the highest in the jejunum and virtually absent in the ileum. Lactase activity and LPH mRNA abundance in suckling rats were 2-3 times more than those of adult rats in all regions of the small intestine. An electromobility shift assays of nuclear proteins revealed that NF-LPH 1 was present in rat small intestine as well as in Caco-2 cells. The amount of NF-LPH 1 binding to the cis-element was also approximately 2-fold more in the intestinal nuclear extracts of suckling rats than that of adult rats. NF-LPH 1 was detected in all regions of the small intestine in both suckling and adult rats. In both cases, the amounts of NF-LPH 1 binding to the cis-element increased from the duodenum to upper jejunum, and decreased toward the ileum. The coordinate postnatal declines of LPH mRNA and NF-LPH 1 expression in various regions of the small intestine suggest that NF-LPH1 might be involved not only in the regulation of postnatal LPH gene expression but in region-specific LPH gene expression as well.