A plasticizer released from IV drip chambers elevates calcium levels in neurosecretory terminals.
We report that intracellular calcium levels rise in mammalian neurosecretory 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-ethylhexyl)phthalate (DEHP). DEHP (800 nM) added to saline solution caused a rise in [Ca(2+)](i) similar to that elicited by the contaminant-containing solution. The extraction of this contaminant 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 [Ca(2+)](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 microM cadmium or by lowering the extracellular free Ca(2+) concentration to 10 microM. Our results suggest that acute alterations in intracellular calcium should be considered in addition to long-term effects when determining the safety of phthalate-containing plastics and that laboratory researchers using plastic perfusion materials consider this potential source of artifactual results.
Tully
K
K
Program in Neuroscience, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.
Kupfer
D
D
Dopico
A M
AM
Treistman
S N
SN
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D004051:Diethylhexyl Phthalate / Q000494:pharmacology*; D004349:Drug Packaging; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D009490:Neurosecretory Systems / Q000187:drug effects / Q000378:metabolism*; D016716:PC12 Cells; D010904:Pituitary Gland, Posterior / Q000187:drug effects / Q000378:metabolism; D010968:Plasticizers / Q000494:pharmacology*; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013056:Spectrophotometry, Ultraviolet; D014407:Tumor Cells, Cultured
D010968:Plasticizers; D004051:Diethylhexyl Phthalate; D002118:Calcium