1,25-Dihydroxyvitamin D3 stimulates Ca-ATPase in a vascular smooth muscle cell line

I have recently shown that a vascular smooth muscle cell line has receptors for 1,25-dihydroxyvitamin D. To examine a possible role of 1,25-dihydroxyvitamin D in the regulation of cellular calcium homeostasis, effect of the sterol on Ca-ATPase activity was studied. 1,25-dihydroxyvitamin D3 stimulated the enzyme activity in a dose dependent manner at 10(-10) and 10(-9) M when the cells were incubated with the sterol for 10 hours. By contrast, 60 minutes incubation of the cells with 1,25-dihydroxyvitamin D failed to stimulate the enzyme activity. Both 25-dihydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 did stimulate the enzyme activity, but at three orders of magnitude higher concentrations. Cycloheximide, at 10(-5)M, abolished the action of 1,25-dihydroxyvitamin D3. These data suggest that 1,25-dihydroxyvitamin D3 stimulates Ca-ATPase activity probably via its receptor and may play a role in regulating cellular calcium homeostasis.