Effects of dexamethasone, calcium and 1,25-dihydroxycholecalciferol on calcitonin and calcitonin gene-related peptide mRNA levels from the CA-77 C cell line.
We used the CA-77 cell, a murine C-cell line derived from a medullary thyroid carcinoma, to study the effects of glucocorticoids, calcium, and vitamin D metabolites on calcitonin (CT) gene expression. Total RNA was isolated, and CT and CT gene-related peptide (CGRP) mRNAs were measured by Northern hybridizations using specific probes. A control mRNA probe (cyclophilin) was used to quantitate the specificity of the changes in CT and CGRP mRNAs. The CA-77 C cell line cultured in basal conditions with a medium deprived of fetal calf serum, but was supplemented by insulin, expressed mainly the CGRP mRNA. Dexamethasone was found to increase both CT and CGRP mRNAs in a time- and dose-dependent way without changing the alternative splicing. A slight but significant increase in the steady-state CT mRNA level was found 3 days after addition of 10(-10) M dexamethasone; the same dose slightly decreased the CGRP mRNA level; concentrations of dexamethasone > or = 10(-9) M elevated both mRNAs. A twelve-fold increase for CT mRNA, and an eightfold increase in CGRP mRNA occurred 3 days after administration of 10(-6) M dexamethasone. Kinetic data revealed inductions of both mRNAs 24 hours after exposure to 10(-7) M dexamethasone, and highest CT and CGRP mRNAs levels were observed after 72 hours of treatment. Calcium from 1-4 mM in short-term (1 hour and 4 hour) or long-term stimulations (1 day and 4 days), with or without dexamethasone cotreatment was ineffective. CT and CGRP mRNAs levels were both half-reduced 48 hours after addition of 10(-7) M 1,25-dihydroxycholecalciferol; this effect was transient, as it disappeared 2 days later.
Collignon
H
H
University of Pierre and Marie Curie, Paris.
Laborie
C
C
Tahri
E H
EH
el M'Selmi
A
A
Garel
J M
JM
D000818:Animals; D015152:Blotting, Northern; D002116:Calcitonin / Q000235:genetics*; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics*; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D003907:Dexamethasone / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D007700:Kinetics; D051379:Mice; D012333:RNA, Messenger / Q000378:metabolism; D013964:Thyroid Neoplasms / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D003907:Dexamethasone; D002116:Calcitonin; D002117:Calcitriol; D015740:Calcitonin Gene-Related Peptide; D002118:Calcium