Calcium-Transport in Quiescent and 1,25-Dihydroxycholecalciferol-Stimulated Human Osteosarcoma Cells. Role in 24 Hydroxylase Enhancement

Summary

The present study evaluates in osteosarcoma cells, the effects of a calcium channel inhibitor nicardipine in 24-hydroxylase activity and ⁴⁵Ca desaturation curve in presence of 1,25-dihydroxycholecalciferol (1,25(OH)₂D₃). This sterol induced an increase in 24-OHase activity and ⁴⁵Ca fluxes. Nicardipine reversed the effect of 1,25(OH)₂D₃ on ⁴⁵Ca fluxes but reinforced the enhancement of the 24-OHase activity. The fact that the effects of 1,25(OH)₂D₃ were reduced by cycloheximide support the hypothesis of a de novo protein synthesis. Our study has allowed us to dissociate the effects of 1,25(OH)₂D₃ on 24-OHase enhancement from those on Ca²⁺ transport.

Key-Words

⁴⁵Ca Kinetics - 1,25-Dihydroxycholecalciferol Osteosarcoma Cells - 24-OHase