Careful    Zinc is one of the most common crustal elements.   It's also involved in a complex set of interactions that can result in production of metallothioneins.


Moreover,  MTs have the capacity to bind both physiological (such as zinc, copper, selenium) and xenobiotic (such as cadmium, mercury, silver, arsenic) heavy metals and experimental data suggest MTs may provide protection against metal toxicity, be involved in zinc and copper regulation, and provide protection against oxidative stress.[4]


I had a Masters student show that this protein occurs in honey bees.  He showed that bees exposed to cadmium produce it.  His study was focused on honey bees in an area downwind from a copper smelter where bees were exposed to arsenic, cadium, zinc, and copper.


But there are trade-offs.  1) zinc at low levels is beneficial, but is toxic to bees at high levels.


2) Activation of production of metallothioneins (based on Richard Cronn's study) resulted in detrimental changes such as decreased levels of zinc and copper - and in fact, these metals all compete for binding sites, so high level exposures to cadmium produced lowered copper and zinc - at sites where smelter pollution actually presented higher than normal exposures to zinc and copper.


3) Note also that many insects and molluscs possess copper-containing hemocyanin for oxygen transport.


4) Bottom line, in normal situations, there is sufficient copper and zinc for bee health.  Adding zinc may result in bee toxicity and/or metallothionein protein production.


One clear result was that LOTS of metallothionein proteins were produced upon bee exposure to cadmium, and copper levels fell off dramatically.


Analysis for metallothionein proteins is rather laborious and costly, copper analysis is a lot easier and cheaper.  In the smelter region, one could identify the most polluted areas, not only be production of metallothioneins, but also by reduced copper levels.



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