title: Developmental differences in the expression of the cholera toxin sensitive subunit (Gs alpha) of adenylate cyclase in the rat small intestine.
abstract: BACKGROUND
  The stimulatory guanosine triphosphate (GTP) binding protein alpha subunit (Gs alpha) of adenylate cyclase is the target protein for cholera toxin.
  
  
  OBJECTIVE
  The expression of this signal transducer was analysed in the small intestine of developing rats by RNA transfer (northern blot) analysis by immunoblotting, and by ADP-ribosylation of membrane proteins.
  
  
  RESULTS
  Intestinal Gs alpha mRNA (about 1.9 kb) was increased in the neonate compared with the adult rat. Two isoforms of Gs alpha proteins, a 45,000 and a 52,000 form, were expressed in the small intestinal epithelial cell and both were ADP-ribosylated by cholera toxin. A significant increase in the larger isoform (52,000) and in its ribosylation was noted in the 2 week old suckling compared with post-weaned older animals. The protein content or ribosylation of the smaller form (45,000) did not significantly change with age.
  
  
  CONCLUSIONS
  These data show that a developmental decline of intestinal Gs alpha expression seems to be, in part, regulated at the mRNA level. An increased Gs alpha expression in the immature intestine may help to explain a previously reported, dose dependent increased adenylate cyclase response and an increase in fluid secretion to cholera toxin in neonates compared with adults.
authors.affiliation: Developmental Gastroenterology Laboratory, Massachusetts General Hospital and Harvard Medical School, Boston, USA.
authors.forename: I R
authors.initials: IR
authors.lastname: Sanderson
authors.forename: Z
authors.initials: Z
authors.lastname: Xu
authors.forename: S W
authors.initials: SW
authors.lastname: Chu
authors.forename: Q Y
authors.initials: QY
authors.lastname: Xie
authors.forename: L J
authors.initials: LJ
authors.lastname: Levine
authors.forename: W A
authors.initials: WA
authors.lastname: Walker
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015152:Blotting, Northern; D002772:Cholera Toxin / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000187:drug effects* / Q000235:genetics; D015870:Gene Expression; D006160:Guanosine Triphosphate / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007421:Intestine, Small / Q000187:drug effects* / Q000378:metabolism*; D012333:RNA, Messenger; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D012333:RNA, Messenger; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases