Restriction of lactase gene expression along the proximal-to-distal axis of rat small intestine occurs during postnatal development.
OBJECTIVE
Developmental changes of lactase activity along the proximal-to-distal axis of the small intestine are poorly understood. A study of delineate lactase gene expression at the cellular level was undertaken.


METHODS
The topographical regulation of lactase was studied in conjunction with sucrase-isomaltase in proximal, middle, and distal segments of 0-, 7-, 14-, 16-, 18-, 21-, and 28-day-old and adult rats using in sity hybridization, immunohistochemistry, and ribonuclease protection assays.


RESULTS
From 0 to 16 days, lactase messenger RNA (mRNA) and protein were abundant along the total length of the small intestine. However, at weaning, lactase mRNA and protein were no longer detectable in the terminal ileum. After 28 days, zones of reduced lactase expression were found in the duodenum and terminal ileum. These zones demonstrated expression of lactase protein in scattered enterocytes along the villus (patchy expression). In contrast, sucrase-isomaltase was first detected at 16 days, with patchy expression along the total small intestine; at 21 days it was abundant.


CONCLUSIONS
Concordant changes in both lactase mRNA and protein detection during development suggest that the horizontal gradient of lactase enzyme expression is dependent on lactase mRNA abundance. Furthermore, zones of patchy lactase expression appear around weaning and flank the area of high lactase expression in the midintestine. Patchy expression is also found for sucrase-isomaltase before weaning.
Rings
E H
EH
Department of Pediatrics, University of Amsterdam, The Netherlands.
Krasinski
S D
SD
van Beers
E H
EH
Moorman
A F
AF
Dekker
J
J
Montgomery
R K
RK
Grand
R J
RJ
Büller
H A
HA
D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D004848:Epithelium / Q000737:chemistry / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007421:Intestine, Small / Q000737:chemistry / Q000201:enzymology*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013394:Sucrase-Isomaltase Complex / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D014886:Weaning; D001616:beta-Galactosidase / Q000032:analysis / Q000235:genetics* / Q000378:metabolism
D012333:RNA, Messenger; D013394:Sucrase-Isomaltase Complex; D001616:beta-Galactosidase