NaF-induced Ca2+ mobilization is dependent upon the culture density in a parathyroid hormone-responsive osteoblast-like cell line.
The effect of NaF on cytosolic free Ca2+ concentrations [( Ca2+]i) was examined in a clonal osteoblast-like cell line (MOB 3-4) loaded with Fura 2. MOB 3-4 cells in a sparse culture, which exhibited neither alkaline phosphatase (ALP) activity nor the response to parathyroid hormone (PTH), responded to NaF (0.1-10 mM) to increase [Ca2+]i transiently. In contrast, the cells in a dense culture, which exhibited both ALP activity and the response to PTH, responded to NaF (above 4 mM) to increase [Ca2+]i slowly. [Ca2+]i in osteoblasts in primary culture slowly increased in response to both NaF (above 4 mM) and PTH (3 U/ml). Thus, the sensitivity and the response of MOB 3-4 cells to NaF and PTH varied with the culture density, and high culture density matured the cells like osteoblasts in primary culture. These NaF-induced Ca2+ mobilizations were not dependent upon external Ca2+ and were enhanced by Al3+ (1 microM), whereas the PTH-induced Ca2+ mobilizations were due to Ca2+ influx. These results suggest that the maturation of MOB 3-4 cells, dependent upon the culture density, modulates intracellular signal transduction pathways and thereby alters the NaF-induced Ca2+ mobilization, and that the culture density must be taken into consideration in studying Ca2+ mobilization in such an osteoblast-like cells line as MOB 3-4 cell line.
Kawase
T
T
Department of Pharmacology, Niigata University School of Dentistry, Gakkocho-dori, Japan.
Ishikawa
I
I
Suzuki
A
A
D000818:Animals; D000831:Animals, Newborn; D001572:Benzofurans; D001842:Bone and Bones / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000494:pharmacology; D016257:Fura-2; D007700:Kinetics; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D012969:Sodium Fluoride / Q000494:pharmacology*
D001572:Benzofurans; D010281:Parathyroid Hormone; D004533:Egtazic Acid; D012969:Sodium Fluoride; D002118:Calcium; D016257:Fura-2