Calcium fluxes and intracellular distribution in clonal osteosarcoma cell lines

Abstract

Calcium efflux patterns were investigated in two clonal osteosarcoma cell lines, ROS 17 2 and ROS 2 3 . Efflux was measured after equilibrating the cells with 45calcium in medium containing 1% or 10% serum. The results of 45calcium efflux were analyzed by fitting them to a model of three exponential terms, using a computer program based on the non-linear least square method. The results indicated the presence of three exchangeable calcium pools which differ in their rate constants of calcium efflux: a “very fast turnover” (S 1) a “fast turnover” (S 2) and a “slow turnover” (S 3). Washing the labelled cells with sucrose solutions, at pH 7.8 and pH 4, removed most of the calcium localized in S 1, indicating that this calcium is membrane bound. The parameters of calcium efflux in ROS cells were found to be different from those measured previously in cultured bone cells: (1) There was no difference between efflux patterns in cells incubated in medium containing 1% and 10% serum; (2) Rates of calcium fluxes were much lower in ROS cells than those in bone cells; and (3) The amount of calcium in S 3 was very small.