Abstract
Intestinal calcium binding protein (iCaBP) is the best known molecular expression of the hormone 1,25 dihydroxyvitamin D (1,25) and its synthesis in response to 1,25 requires the presence of specific 1,25 receptor macromolecules (1.25R). In rats, the developmental appearance of the 1.25R, iCaBP and its responsiveness to 1,25 occur around weaning. To test the hypothesis that in the fetal sheep, where there is evidence for a role of fetal 1,25 in mineral metabolism, there would be prenatal appearance of intestinal 1,25R and iCaBP, we isolated cytosolic intestinal 1,25R from samples of fetal (F:n=8) and maternal (M:n=5) small intestinal mucosa at 138d of gestation (term=145d). 1,25R were characterized by sedimentation coefficient (Sed), Scatchard analysis of saturation binding data and DNA-cellulose affinity chromatography (DNAcell).
Gel filtration of F and M intestinal mucosal cytosols revealed a high affinity calcium binding protein in the 12,000 molecular weight region that demonstrated decreased anionic charge when bound to calcium (Ca) with the following elution profile on DEAE-A25 chromatography: (-Ca:elution at 0.2M NaCl / +Ca:elution in void volume). The purified apoprotein exhibited an acidic PI of 5.2 on isoelectric focusing.
Conclusion: These data suggest that 1,25 is biologically active in the ovine fetal intestine.
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Ross, R., Chen, H. & Florer, J. EVIDENCE THAT 1,25 DIHYDROXYVITAMIN D3, IS BIOACTIVE IN THE FETAL SHEEP INTESTINE. Pediatr Res 21 (Suppl 4), 276 (1987). https://doi.org/10.1203/00006450-198704010-00655
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DOI: https://doi.org/10.1203/00006450-198704010-00655