Vitamin D increases tight-junction conductance and paracellular Ca2+ transport in Caco-2 cell cultures.
We investigated the effects of 1 alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] on paracellular intestinal Ca2+ absorption by determination of transepithelial electric resistance (TEER), as a measure of tight-junction ion permeability and bidirectional transepithelial 45Ca2+ fluxes in confluent Caco-2 cell cultures. The rise of TEER to steady-state levels of approximately 2,000 omega.cm2 was significantly attenuated by 1,25(OH)2D3 (by up to 50%) in a dose-dependent fashion between 10(-11) and 10(-8) M. Synthetic analogs of 1,25(OH)2D3, namely, 1 alpha,25-dihydroxy-16-ene,23-yne-vitamin D3 and 1 alpha,25-dihydroxy-26,27-hexafluoro-16-ene,23-yne-vitamin D3, 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 45Ca2+ fluxes. Although 1,25(OH)2D3 also induced cellular 45Ca2+ 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 Ca2+ transport could be detected. Therefore stimulation of Ca2+ 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.
Chirayath
M V
MV
Department of General and Experimental Pathology, University of Vienna, Austria.
Gajdzik
L
L
Hulla
W
W
Graf
J
J
Cross
H S
HS
Peterlik
M
M
D001692:Biological Transport / Q000187:drug effects; D018938:Caco-2 Cells; D002117:Calcitriol / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology; D012413:Rubidium / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects / Q000502:physiology*; D014807:Vitamin D / Q000494:pharmacology / Q000502:physiology*
D014807:Vitamin D; D002117:Calcitriol; D012413:Rubidium; D002118:Calcium