EFFECTS OF AN ENVIRONMENTAL TOXICANT ON ULTRASTRUCTURE IN PARAMECIUM-CAUDATUM AND THE PROTECTIVE EFFECT OF DISSOLVED CALCIUM

Acute exposures of the unicellular organism Paramecium caudatum cells to the carcinogen quinoline gave rise to disruption of inner and outer mitochondrial membranes while leaving the nuclear, cytoplasmic and ci liary membrane systems unchanged, as shown by transmission electron mi croscopy (TEM) of treated and control cells. Time course TEM studies s howed that quinoline entered cells and began to disrupt inner mitochon drial membranes within 10 min of treatment. Subsequent effects include d swelling of the mitochondria and eventual lysis. Additions of extrac ellular Ca2+ to the quinoline treatments attenuated the mitochondrial membrane damage so that no difference was observed between controls an d the quinoline/calcium treatments. Experiments using proton nuclear m agnetic resonance spectrometry and ultraviolet absorption spectrophoto metry suggested that the quinoline-free base interacted weakly with ca lcium ions in buffered aqueous solution, causing changes in partition equilibria between the organic and aqueous phases. These results indic ated that the protective effect of calcium involved changes in quinoli ne solubility and resultant decreases in intracellular quinoline conce ntrations in exposed cells.