Effect of a platinum chemotherapy drug on intracellular elements during the cell cycle, using X-ray microanalysis

Intracellular elemental concentrations were measured in the cytoplasm, nucleus and nucleolus of cultured Chinese hamster ovary (CHO) cells, using energy dispersive electron probe X-ray microanalysis and transmission electron microscopy. Synchronous CHO cell populations were analyzed at different times during the growth cycle. The elements K, P, Mg and Zn were all more concentrated in the nucleus and nucleolus than in the cytoplasm, while no specific subcellular compartmentalization was evident for the elements Na, Cl, Ca, Fe and S. Significant changes in intracellular elemental concentrations were associated with the progression of cells from G1 phase to S phase of the growth cycle. Most significant were the effects on the monovalent ions, Na, K and Cl. The effect of a second generation platinum chemotherapy agent, cis-dichloro-bis (isopropylamine) trans-dihydroxy platinum IV (iproplatin) on intracellular elements was investigated by analyzing subcellular compartments of drug-treated synchronous CHO cell populations. Changes in intracellular elemental levels occurred, most notably in the nucleus of G1 phase cells, when a general depletion of most essential elements was evident. Attempts to analyze cells for their Pt content proved disappointing, since quantitation for Pt was not possible. However, measurement of Pt peak/background ratio yielded significant Pt peaks on analyzing lysosomes of cells treated with high concentrations of iproplatin. These Pt peaks were associated with high levels of S and Fe.