A plasticizer released from IV drip chambers elevates calcium levels in neurosecretory terminals

We report that intracellular calcium levels rise in mammalian neurosecretor y terminals and in cultured pheochromocytoma cells during acute exposure to physiological medium incubated in IV drip chambers. The agent responsible for this effect is shown to be di(2-erhylhexyl)phthalate (DEHP). DEHP (800 nM) added to saline solution caused a rise in [Ca2+](i) similar to that eli cited by the contaminant-containing solution. The extraction of this contam inant from the IV drip chamber, as measured by spectrophotometry, was time- dependent and was markedly accelerated by the presence of 50 mM ethanol in the solution. Larger [Ca2+](i) increases were observed in terminals exposed to solutions incubated in IV drip chambers for greater durations. The rise in calcium requires transmembrane calcium flux through membrane channels, as the response is blocked by either 100 muM cadmium or by lowering the ext racellular free Ca2+ concentration to 10 muM. Our results suggest that acut e alterations in intracellular calcium should be considered in addition to long-term effects when determining the safety of phthalate-containing plast ics and that laboratory researchers using plastic perfusion materials consi der this potential source of artifactual results, (C) 2000 Academic Press.