Single and combined effects of heavy metals and hormones on lysosomes of haemolymph cells from the mussel Mytilus galloprovincialis

Effects of heavy metals on lysosomes were studied in living cells from the mussel (Mytilus galloprovincialis Lam.). Haemolymph cells were obtained from the mussel adductor muscle, stained with neutral red (NR), and analysed by digital imaging to evaluate NR retention times within lysosomes. Exposure to Hg2+, Cd2+ and Cu2+ induced a reduction of NR retention time, indicating lysosomal membrane destabilisation. The intensity of these effects was correlated with the metal affinity for sulfhydryls. In contrast, Zn2+ showed no effect on lysosomes. Moreover, 200 muM Zn2+ protected lysosomes against the effects of Cd2+ and Cu2+, but not against Hg2+. Cell loading with the fluorescent pH probe Lyse Sensor followed by digital imaging showed a rise of lysosomal pH induced by Cd2+ and Hg2+, while Zn2+ prevented the effect of Cd2+ and also partially that of Hg2+ The different protective effect of Zn2+ against Hg2+ suggests a dual action of Hg2+ on lysosomes, possibly involving both membrane destabilisation and proton pump inhibition. Cell exposure to 17 beta -estradiol also caused a reduction of NR retention time, which was synergistic to that of Hg2+ This suggests a common pathway between metals and hormone, possibly involving Ca2+ signaling.