Specific 1,25 (OH) 2D3-mediated regulation of transcellular calcium transport in Caco-2 cells
Fleet, J.C.; Wood, R.J.
American Journal of Physiology 276(4): G958-G964
1999
ISSN/ISBN: 0002-9513 PMID: 10198340 Document Number: 505184
Calcium transport in the apical-to-basolateral (A-to-B) or B-to-A direction was examined in cells treated with 10 nM 1,25-dihydroxyvitamin D3 for up to 72 h. Net A-to-B calcium transport was positive at all time points and increased from 0.14 ± 0.06 to 0.50 ± 0.01 nmol well-1 min-1 after 72 h of calcitriol treatment. Neither phenol red transport nor transepithelial electrical resistance was altered by calcitriol treatment, suggesting that the increase in net A-to-B calcium transport was not due to paracellular movement. Neither 25-hydroxyvitamin D3 nor 24,25-dihydroxyvitamin D3 (100 nM, 48 h) alters basal or calcitriol-stimulated A-to-B calcium transport. Treatment with the calmodulin antagonist trifluoperazine (50 mM) reduced calcitriol-stimulated A-to-B Ca transport by 56%. The transcription inhibitor actinomycin D inhibited calcitriol-regulated A-to-B calcium transport as well as calbindin D9k and 24-hydroxylase mRNA accumulation. These data demonstrate that calcitriol-mediated A-to-B calcium transport in Caco-2 cells is a specific, transcellular process that requires transcriptional events normally mediated through the vitamin D recector. Reprinted by permission of the publisher.