Ontogeny of procholecystokinin maturation in rat duodenum, jejunum, and ileum.
Expression and processing of procholecystokinin (proCCK) in rat intestine during development were examined using sequence-specific immunoassays, cleavage with processing-like enzymes, and chromatography. Fetal proCCK concentrations were similar in duodenum, jejunum, and ileum, but the maturation to CCK followed different courses: duodenal CCK increased from 14 pmol/g in the fetus to 86 pmol/g 4 days after birth and then declined to 17 pmol/g in the adult. In jejunum, CCK varied from 34 pmol/g in the fetus to 127 pmol/g at day 7, decreased to 54 pmol/g at day 21, and increased again to 93 pmol/g in the adult. Ileal CCK decreased from 20 pmol/g in the fetus to 10 pmol/g postnatally. Whereas duodenal proCCK after birth matured completely to carboxyamidated CCK, jejunoileal proCCK matured only partially. Chromatography showed an increase of tyrosine-sulfation and proteolytic processing of N-terminal sequences. At day 7 jejunal cholecystokinin octapeptide (CCK-8) constituted only a minute fraction of the carboxyamidated CCK, of which less than half was sulfated. However, in the adult jejunum, CCK-8 constituted a significant fraction, which was completely sulfated. It is concluded that the CCK gene is well expressed at propeptide level in the fetal small intestine. Postpartum maturation of proCCK, however, is late and differs in the three parts of the small intestine. The belated maturation supports the hypothesis that factors other than CCK regulate pancreatic growth in fetal and neonatal life.
Rehfeld
J F
JF
Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Denmark.
Bardram
L
L
Hilsted
L
L
D000595:Amino Acid Sequence; D000818:Animals; D002766:Cholecystokinin / Q000032:analysis* / Q000096:biosynthesis / Q000378:metabolism; D004386:Duodenum / Q000737:chemistry*; D005260:Female; D005333:Fetus / Q000378:metabolism; D005755:Gastrins / Q000096:biosynthesis; D007082:Ileum / Q000737:chemistry*; D007583:Jejunum / Q000737:chemistry*; D008969:Molecular Sequence Data; D011247:Pregnancy; D011498:Protein Precursors / Q000032:analysis* / Q000378:metabolism; D051381:Rats
D005755:Gastrins; D011498:Protein Precursors; C060249:procholecystokinin; D002766:Cholecystokinin