In:
American Journal of Physiology-Gastrointestinal and Liver Physiology, American Physiological Society, Vol. 274, No. 2 ( 1998-02-01), p. G389-G396
Kurzfassung:
We investigated the effects of 1α,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] on paracellular intestinal Ca 2+ absorption by determination of transepithelial electric resistance (TEER), as a measure of tight-junction ion permeability and bidirectional transepithelial 45 Ca 2+ fluxes in confluent Caco-2 cell cultures. The rise of TEER to steady-state levels of ∼2,000 Ω ⋅ cm 2 was significantly attenuated by 1,25(OH) 2 D 3 (by up to 50%) in a dose-dependent fashion between 10 −11 and 10 −8 M. Synthetic analogs of 1,25(OH) 2 D 3 , namely, 1α,25-dihydroxy-16-ene,23-yne-vitamin D 3 and 1α,25-dihydroxy-26,27-hexafluoro-16-ene,23-yne-vitamin D 3 , exhibited similar biopotency, whereas their genomically inactive 1-deoxy congeners were only marginally effective. Enhancement of transepithelial conductance of Caco-2 cell monolayers by vitamin D was accompanied by a significant increase in bidirectional transepithelial 45 Ca 2+ fluxes. Although 1,25(OH) 2 D 3 also induced cellular 45 Ca 2+ uptake from the apical aspect of Caco-2 cell layers and upregulated the expression of calbindin-9kDa mRNA, no significant contribution of the Ca 2+ -adenosinetriphosphatase-mediated transcellular pathway to transepithelial Ca 2+ transport could be detected. Therefore stimulation of Ca 2+ fluxes across confluent Caco-2 cells very likely results from a genomic effect of vitamin D sterols on assembly and permeability of tight-junctional complexes.
Materialart:
Online-Ressource
ISSN:
0193-1857
,
1522-1547
DOI:
10.1152/ajpgi.1998.274.2.G389
Sprache:
Englisch
Verlag:
American Physiological Society
Publikationsdatum:
1998
ZDB Id:
1477329-6
SSG:
12
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