Cadmium delays growth hormone expression during rainbow trout development

Growth hormone (GH) mRNAs were first detected in rainbow trout Oncorhynchus mykiss during organogenesis (stage 29) within a control group while GH expression in cadmium exposed embryos was not detected until a later organogenic period (stage 31). GH transcripts were subsequently detected at all further developmental stages analysed within both treatment groups. These included hatching (stage 32), larval development (stages 33, 34, 35 and 36) and first feeding (stage 37). These results confirm that the GH axis is functional during early rainbow trout development and demonstrate an in vivo endocrine disrupting capacity at the molecular level for cadmium in teleosts. This is of particular relevance to freshwater habitats as heavy metal induced endocrine disruption may be a contributing factor in the decline of salmonid populations.