Early manifestations of vitamin D effects in rat osteogenic sarcoma cells

We have recently demonstrated that 48 hour exposure of ROS 17/2 cells to low concentrations of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) (1.0 pg/ml) stimulated the cellular accumulation of 45Ca, and exposure to high concentrations (160 pg/ml) inhibited such accumulation. In the present study, short-term (15 min) effects of the sterol on 45Ca accumulation in ROS 17/2 cells were compared with the long-term (48 hours) effects in order to clarify mechanisms responsible for 1,25(OH)2D3 control of calcium metabolisms in ROS 17/2 cells. ROS 17/2 cells were grown for 48 hours in the presence and absence of 1,25(OH)2D3 and then incubated for an additional 15 min in the presence and absence of 1,25(OH)2D3 immediately before measuring 45Ca accumulation. Cellular 45Ca was measured after incubating the cells in the medium containing 0.5 microCi/ml of 45CaCl2 for 4 min at 25 degrees C. The effect of actinomycin D was determined by preincubating the cells in 0.1 microgram/ml of actinomycin D for 45 min at 25 degrees C. Exposure to low concentrations (1.0 pg/ml) of 1,25(OH)2D3 for either 48 hours or 15 min increased 45Ca in the cells by 10-20%. An additional 15 min exposure following 48 hour exposure yielded an increase in the cellular 45Ca similar to that after 48 hours or 15 min exposure. Exposure to high concentrations (160 pg/ml) for either 48 hour or 15 min decreased cell 45Ca by approximately 20%. An additional 15 min exposure to the high concentrations did not change the 48 hour effect. Actinomycin D reversed early inhibitory effects of high concentrations, but had no effect on the early stimulatory effects of low concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)