Increased NHE2 expression in rat intestinal epithelium during ontogeny is transcriptionally mediated.
We have previously described changes in intestinal brush-border membrane vesicle (BBMV) Na+/H+ exchange activity and characterized Na+/H+ exchanger (NHE3) expression during rat ontogeny. The current studies were designed to investigate developmental changes in NHE2 expression in rat intestine. In previous studies, pH-dependent uptake of Na+ in jejunal BBMV utilizing HOE-694 inhibition demonstrated that NHE2 functional protein levels were lowest in 2-wk-old rats, higher in 3-wk-old and adult rats, and highest in 6-wk-old rats [Collins et al. Am. J. Physiol. 273 (Cell Physiol. 42): C1937-C1946, 1997]. In the current investigation, Northern blot analyses showed that NHE2 mRNA levels in the jejunum were similar in 6-wk-old, adult, and 3-wk-old rats and three- to fivefold lower in 2-wk-old rats. In situ hybridization of 2- and 6-wk-old rat intestine with NHE2-specific probes confirmed Northern blot observations. Polyclonal antibodies were developed against an NHE2-specific peptide from amino acids 652-661. Western blots with NHE2 antiserum showed that the intensity of a specific 90-kDa band was lowest in 2-wk-old animals and four- to sixfold higher in 3- and 6-wk-old and adult animals. Immunohistochemical analysis showed specific staining of NHE2 antiserum to only the apical intestinal membrane. Furthermore, nuclear run-on analyses showed a 1.7-fold higher NHE2 transcription rate in 6-wk-old rats than in 2-wk-old rats. Overall, the current data suggest that increases in NHE2 expression upon weaning are mediated by increased gene transcription.
Collins
J F
JF
Departments of Pediatrics and Physiology, Steele Memorial Children's Research Center, University of Arizona Health Sciences Center, Tucson, Arizona 85724, USA.
Kiela
P R
PR
Xu
H
H
Zeng
J
J
Ghishan
F K
FK
D000375:Aging; D000818:Animals; D018507:Gene Expression Regulation, Developmental; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000254:growth & development / Q000378:metabolism*; D007583:Jejunum / Q000254:growth & development / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic
D012333:RNA, Messenger; C513110:Slc9a2 protein, rat; D017923:Sodium-Hydrogen Exchangers