H-1 NMR spectroscopic investigations of tissue metabolite biomarker response to Cu(II) exposure in terrestrial invertebrates: identification of free histidine as a novel biomarker of exposure to copper in earthworms

High resolution H-1 NMR spectroscopy of biofluids, cells and tissue extracts allows rapid, non-destructive analysis fdr a wide range of metabolites and organic compounds with minimal sample pre-treatment. We have applied high resolution 1H NMR spectroscopy to investigate the biochemical effects of Cu(ll) in two earthworm species Eisenia andrei (n=78) and Lumbricus rubellus (n=45) exposed under laboratory and semi-field conditions respectively. The most marked metabolic response was the elevation of endogenous whole body free histidine in animals which positively correlated with increasing copper exposure and total copper burden in the semi-field experiment. Histidine forms thermodynamically stable copper complexes under a wide range of physico-chemical conditions and we proposed that the elevation of free histidine in response to copper challenge provides an energetically 'low-cost' detoxification mechanism. Histidine elevation may also provide a novel molecular biomarker of Cu(ll) exposure in environmental situations.