Copper deficiency in rodents alters dopamine -mono-oxygenase activity, mRNA and protein level

Abstract

Cu is an essential cofactor for at least twelve mammalian enzymes including dopamine β-mono-oxygenase (DBM), which converts dopamine (DA) to noradrenaline (NA). Previous studies reported that certain Cu-deficient (Cu-) rat tissues have lower NA and higher DA than Cu-adequate (Cu+) tissues, suggesting that DBM function was impaired. However, in vitro studies suggested that DBM activity is higher in Cu- tissue. Experiments were conducted on adrenal glands (AG), medulla oblongata/pons (MO), vas deferens (VD) and heart (HT) from a single rat experiment to provide data to help clarify this puzzling contradiction. In vitro DBM activity assays showed Cu- samples had significantly higher activity than Cu+ samples in both AG and MO, but not VD. Activity data were confirmed by Western immunoblots. Quantitative real-time PCR demonstrated higher DBM mRNA in Cu- tissues but unaltered levels of several other cuproenzymes and Cu-binding proteins. Previous pharmacological data implied that high DBM was associated with low NA. HPLC analyses confirmed that NA and DA levels in Cu MO, VD and HT were significantly lower and higher, respectively, than in Cu+ tissues. However, the NA content of AG was not statistically lower. Furthermore there was no correlation between higher DBM mRNA and lower NA in four Cutissues. Adequate dietary Cu is essential to support DBM function in vivo but additional studies are needed to determine the mechanism for increased DBM transcription associated with Cu deficiency.