Metallothionein-bound cadmium in the gut of the insect Orchesella cincta (Collembola) in relation to dietary cadmium exposure

Metallothionein is considered to be a potential biomarker for heavy metal e xposure in the terrestrial environment. However, limited information is ava ilable on metallothioneins from insects, a major class of terrestrial inver tebrates. In this study we have quantified metallothioneins in the springta il Orchesella cincta by determining metallothionein-bound cadmium after sep aration of these proteins using gel filtration and reversed phase chromatog raphy from total body homogenates of animals dietary exposed to different c oncentrations of cadmium. Furthermore, we have studied in more detail where cadmium and metallothionein-bound cadmium is located within this animal. T he concentration of metallothionein-bound cadmium increases with the exposu re concentration in the same way as the total internal concentration. Both reach a plateau at an exposure concentration of approximately 1.0 mu mol Cd /dry food. Cadmium is primarily located within the gut of O. cincta and iso lation of metallothionein from this organ gives results identical to isolat ions from total bodies. Based on this results an estimation of the metallot hionein level at the highest exposure concentration results in a concentrat ion of about 115 mu g metallothionein/g fresh gut. The O. cincta metallothi onein gives the possibility of using this protein as a biomarker for heavy metal exposure in soil insects. (C) 2000 Elsevier Science Inc. All rights r eserved.