1,25-Dihydroxycholecalciferol regulates rat intestinal calbindin D9k posttranscriptionally.
To determine whether calbindin D9k (CaBP) is subject to posttranscriptional control, 6-wk-old Sprague Dawley-derived rats were fed one of three purified diets, 1.5% Ca and 3.0% Ca, mostly as carbonate, and 2.9% Ca, mostly as gluconate. Two weeks later, 5-cm segments of duodenum, jejunum, ileum, cecum and colon were obtained and analyzed for CaBP and CaBP-mRNA. Analysis of the steady-state distribution of CaBP-mRNA and of CaBP revealed a statistically significant (r = 0.95; P < 0.01) linear relationship between CaBP-mRNA and CaBP. When, however, animals that had been fed the 1.5% Ca diet received by intrajugular injection 1.2 nmol 1,25-dihydroxycholecalciferol [1.25-(OH)2-D3] and their CaBP-mRNA and CaBP were analyzed as a function of time after 1,25-(OH)2-D3 administration, the kinetic response of the two molecules differed. The CaBP-mRNA increased linearly by approximately 68% for 4 h after administration and then declined over the next 6 h to a concentration below the preinjection value. Thus, appearance and disappearance of CaBP-mRNA approximated 17% x h(-1). The CaBP, however, increased steeply to 80% above preinjection concentration until 2 h postinjection, i.e., at a rate of 40% x h(-1). Thereafter, CaBP decreased to 35% above the preinjection value between 5 and 10 h postinjection (2.5% x h(-1)). These findings are consistent with a 1,25-(OH)2-D3-mediated posttranscriptional regulation of CaBP concentrations, because the 1,25-(OH)2-D3-mediated increase in CaBP-mRNA is not reflected in an immediately changed CaBP level.
Duflos
C
C
Ecole Pratique des Hautes Etudes, INSERM U 45, Hôpital Edouard Herriott, Lyon, France.
Bellaton
C
C
Baghdassarian
N
N
Gadoux
M
M
Pansu
D
D
Bronner
F
F
D000818:Animals; D001483:Base Sequence; D064026:Calbindins; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000008:administration & dosage; D002432:Cecum / Q000378:metabolism; D003106:Colon / Q000378:metabolism; D015342:DNA Probes; D004032:Diet; D004386:Duodenum / Q000187:drug effects / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects*; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
D064026:Calbindins; D015342:DNA Probes; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; C576508:S100g protein, rat; D002117:Calcitriol; D002118:Calcium