Short treatment of osteoclasts in bone marrow culture with calcitonin causes prolonged suppression of calcitonin receptor mRNA.
Cells exhibiting osteoclast characteristics of calcitonin receptors (CTRs) and tartrate-resistant acid phosphatase (TRAP) histochemistry are formed in murine bone marrow cultures treated with 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. We have previously demonstrated that CTR mRNA is highly expressed in these cultures. The aim of this study was to investigate homologous regulation of the CTR, and regulation of TRAP expression in osteoclast-like cells after brief treatment with salmon CT (sCT). Murine bone marrow cells were cultured in 9 cm dishes in the presence of 10 nmol/L 1,25-(OH)2D3. On day 6 of culture, when multinucleated cells were abundant, the cells were treated with 1 nmol/L sCT for 1 h. Both control and treated cells were then harvested at intervals up to 72 h posttreatment, and both CTR and TRAP mRNA levels assessed by reverse-transcription PCR (RT-PCR). In parallel cultures, cells with CTR expression detectable by autoradiography, and TRAP positivity by histochemistry, were counted. The effects of brief sCT treatment could be seen 6 h after treatment when the CTR RT-PCR product was markedly reduced. Total recovery of CTR mRNA levels had not occurred even after 72 h. Calcitonin treatment had little effect on TRAP mRNA levels. There was no difference in the numbers of multinucleated TRAP(+) osteoclast-like cells between treated and control cells. These results indicate that brief sCT treatment, while not influencing multinucleated osteoclast-like cell number, causes specific, acute reduction of CTR mRNA in bone marrow culture-derived osteoclasts. The prolonged decrease in CTR mRNA levels suggests that recovery may require new osteoclast formation, and indicates that regulation of the CTR in cells of the osteoclast lineage is different from that in nonosteoclastic cells and tissues.
Rakopoulos
M
M
St. Vincent's Institute of Medical Research, St. Vincent's Hospital, Victoria, Australia.
Ikegame
M
M
Findlay
D M
DM
Martin
T J
TJ
Moseley
J M
JM
D000135:Acid Phosphatase / Q000187:drug effects* / Q000378:metabolism; D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D001853:Bone Marrow / Q000187:drug effects*; D001854:Bone Marrow Cells; D002116:Calcitonin / Q000494:pharmacology*; D002478:Cells, Cultured; D015536:Down-Regulation; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D018003:Receptors, Calcitonin / Q000187:drug effects* / Q000235:genetics; D013644:Tartrates / Q000494:pharmacology
D000700:Analgesics; D012333:RNA, Messenger; D018003:Receptors, Calcitonin; D013644:Tartrates; C028815:salmon calcitonin; D002116:Calcitonin; D000135:Acid Phosphatase