1α,25‐dihydroxyvitamin D 3 rapidly alters phospholipid metabolism in the nuclea envelope of osteoblasts

1α,25‐Dihydroxyvitamin D 3 (1α, 25‐(OH) 2 D 3 ) 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) 2 D 3 ‐induced changes in the calcium, the effect of the hormone on phospholipid metabolism in isolated osteoblast nuclei wa assessed. 1α,25 (OH) 2 D 3 , 20 nM, increased inositol triphosphate levels in the nuclei after 5 min of treatment. The biologically inactive epimer, 1β,25‐(OH) 2 D 3 , 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) 2 D 3 , 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) 2 D 3 , suggesting that these two agents increase nuclear calcium in these osteoblast‐like cells by similar mechanisms. In summary, 1α,25‐(OH) 2 D 3 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) 2 D 3 and ATP effects of nuclear calcium may be mediated by changes in phospholipid metabolism in the nuclei of these osteoblastlike cells. © Wiley‐Liss, Inc.