Triamcinolone acetonide induces transient changes in accumulation and fluxes of calcium in cultured bone cells

Abstract

The effects of triamcinolone acetonide on the pattern of 45calcium efflux were investigated in cultured bone cells. Efflux was measured after equilibrating the cells with 45calcium for 24 hours and a short (3 hours) or a long (24 hours) preincubation with the hormone. The results were analyzed by fitting them to a model of three exponential terms, using a computer program based on the non-linear least square method. As reported previously the results indicated the presence of three exchangeable calcium pools which differ in their rates of calcium exchange. A short preincubation with the hormone (3 hours) caused the following changes: (1) A marked increase in the amount of exchangeable calcium in the “slow turnover” calcium pool (S 3) which is probably in the mitochondria. (2) A lesser but significant increase in the amount of calcium in the “fast turnover” calcium pool (S 2) which is probably the calcium in the cytosol. (3) An increase in the rates of calcium exchange between S 2 and the medium (ϱ 20) and between S 3 and S 2 (ϱ 32). All these changes were transient. After 24 hours of preincubation with triamcinolone acetonide the amounts of calcium in S 2 and S 3 decreased below the control levels and the fluxes were not significantly different from those of the controls.