Differential responsiveness of intestinal epithelial cells to 1,25-dihydroxyvitamin D3--role of protein kinase C.
Non-transformed rat intestinal epithelial cell (IEC) lines were used to study the action of 1,25-dihydroxyvitamin D(3) (1,25(OH)2D) in the intestine. The capacity of 1,25(OH)2D to increase the expression of the cytochrome P450 component of the vitamin D 24-hydroxylase (CYP24) was determined in IEC-6 and IEC-18 cell lines. In IEC-6 cells, which are derived from crypt cells isolated from the whole small intestine, 1,25(OH)2D markedly increased expression of CYP24 protein and mRNA within 12 h. In contrast, in IEC-18 cells, which are derived from crypt cells from the ileum only, 1,25(OH)2D did not increase expression of CYP24 until 24-48 h. The maximal levels of CYP24 mRNA seen in the IEC-18 cells were only 31% of the maximal levels seen in the IEC-6 cells. In the presence of 1,25(OH)2D, phorbol esters rapidly increased CYP24 mRNA levels in IEC-18 cells from almost undetectable to levels seen in IEC-6 cells. Protein kinase inhibitors abolished the stimulation by 1,25(OH)2D and by phorbol esters in both cell lines. Stimulation of mRNA levels by phorbol esters required new protein synthesis but stimulation by 1,25(OH)2D did not. These studies demonstrated that the rapid action of 1,25(OH)2D in IEC-6 cells is related to the activation of protein kinase C, an event which is missing in the IEC-18 cells. This differential response to 1,25(OH)2D probably takes place at a post-receptor site, since the number of vitamin D receptors in each cell line was found to be similar.
Geriatric Research, Education, and Clinical Center, St Louis VA Medical Center, St Louis, Missouri 63125, USA.
H J
HJ
Armbrecht
M A
MA
Boltz
T L
TL
Hodam
V B
VB
Kumar
D000818:Animals; D015152:Blotting, Northern; D002117:Calcitriol / Q000494:pharmacology*; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D015151:Immunoblotting; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D011493:Protein Kinase C / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D018167:Receptors, Calcitriol / Q000378:metabolism; D013250:Steroid Hydroxylases / Q000235:genetics / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D065668:Vitamin D3 24-Hydroxylase
D012333:RNA, Messenger; D018167:Receptors, Calcitriol; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D065668:Vitamin D3 24-Hydroxylase; D011493:Protein Kinase C; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate