OBJECTIVETo study the mechanism of lactose intolerance (LI) by cloning the mouse lactase cDNA and recombining a vector. METHODS Total murine RNA was isolated from the small intestine of a 4-week-old BALB/c mouse (d). Gene-specific primers were designed and synthesized according to the cDNA sequences of lactase-phlorizin hydrolase (LPH) in human, rat, and rabbit. A coding sequence (CDS) fragment was obtained using RT-PCR, and inserted into a clone vector pNEB-193, then the cDNA was sequenced and analyzed using bioinformatics.

RESULTSThe cDNA from the BALB/c mouse with 912 bp encoding 303 amino acid residues. Analysis of the deduced amino acid sequence using bioinformatics revealed that this cDNA shared extensive sequence homology with human LPH containing a conserved glycosyl hydrolase family 1 motif important for regulating lactase intolerance.

CONCLUSIONBALB/c mouse LPH cDNA (GenBank accession No: AY751548) provides a necessary foundation for study of the biological function and regulatory mechanism of the lactose intolerance in mice.

Animals ; Cloning, Molecular ; DNA, Complementary ; Humans ; Lactase-Phlorizin Hydrolase ; genetics ; Mice ; Mice, Inbred BALB C

OBJECTIVE: The specific activity of lactase-phlorizin hydrolase (LPH) is very high at birth and sharply declines after weaning, producing lactose intolerance. The prevalence of lactose intolerance is up to 85% in Korean adults. Molecular basis of the regulatory mechanisms responsible for the decline of LPH specific activity is still unknown. In order to elucidate the molecular mechanisms regulating the LPH expression during development, LPH specific activity and mI4NA level of Korean fetal and adult intestines were compared. METHODS: 20 fetal small intestines (16-27 weeks) were obtained during therapeutic abortion and were divided into 3 equal length. 20 adult jejunal tissues were obtained from patients without small intestinal disease during laparotomy. Mucosal homogenates were prepared for dissacharidases specific activities measurement and total RNA was extracted for northern and slot hvbridization. LPH mRNA level was measured by laser densitometer. RESULTS: LPH specific activities of proximal, middle and distal portion of fetal intestines (n=20) were 36.2 +/- 22.5, 38.6 +/- 23.2 and 23.2 +/- 19.9 mu/mg protein, respectively. LPH specific activity of adult jejunum (n=8) was 5.9 +/- 1.8 mu/mg protein and significantly (p<0.05) lower than those of fetal intestines. However, there was no significant difference in sucrase and trehalase specific activities between fetal intestines and adult jejunum. Although LPH specific activity of adult jejunum was lower than those of fetal intestines, LPH mBNA level of adult jejunum was as high as those of fetal intestines. CONCLUSION: These results show that LPH specific activity and mRNA level do not parallel, indicating the posttranscriptional control of fetal development of LPH expression.
Abortion, Therapeutic ; Adult* ; Female ; Fetal Development ; Fetus* ; Humans ; Intestinal Diseases ; Intestine, Small* ; Intestines ; Jejunum ; Lactase* ; Lactase-Phlorizin Hydrolase ; Lactose Intolerance ; Laparotomy ; Parturition ; Pregnancy ; Prevalence ; RNA ; RNA, Messenger* ; Sucrase ; Trehalase ; Weaning