1α,25‐dihydroxyvitamin D3 rapidly alters phospholipid metabolism in the nuclea envelope of osteoblasts

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Abstract
1α,25-Dihydroxyvitamin D3 (1α, 25-(OH)2D3) has been shown to increase cytosolic calcium and inositol trophosphate levels in rat osteosarcoma cells (ROS 17/2.8) and to increase nuclear calcium in these cells. To determine the mechanism(s) of 1α, (OH)2D3-induced changes in the calcium, the effect of the hormone on phospholipid metabolism in isolated osteoblast nuclei wa assessed. 1α,25 (OH)2D3, 20 nM, increased inositol triphosphate levels in the nuclei after 5 min of treatment. The biologically inactive epimer, 1β,25-(OH)2D3, had no significant effect on inositol triphosphate levels. ATP, 1 mM, also increased inositol triphosphate levels in the isolated nuclei after 5 min. 1α,25-(OH)2D3, 20 nM, increased calcium in the isolated nuclei in the presence but not in the absence of extranuclear calcium with 5 min. Nuclear calcium was also increased within 5 min by ATP, 1 mM, and inositol triphosphate, 1 mM. The effects of ATP on nuclear calcium was not additive with 1α, 25-(OH)2D3, suggesting that these two agents increase nuclear calcium in these osteoblast-like cells by similar mechanisms. In summary, 1α,25-(OH)2D3 amd ATP rapidly increase inositol triphosphate levels in isolated from ROS 17/2.8 cells. The hormone, the nucleotide, and the inositol phospholipid nuclear calcium. Thus, the 1α,25-(OH)2D3 and ATP effects of nuclear calcium may be mediated by changes in phospholipid metabolism in the nuclei of these osteoblastlike cells. © Wiley-Liss, Inc.

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