Modulation of the effects of methylmercury on rat neurodevelopment by co-exposure with Labrador Tea (Rhododendron tomentosum ssp. subarcticum)

Co-administration of a Rhododendron tomentosum extract does not affect mercury tissue concentrations and excretion rate in methylmercury-treated adult male rats

“…In a controlled exposure study, tea consumption was associated with higher blood mercury levels in volunteers who ate fish [22], while higher maternal blood mercury levels were associated with herbal tea consumption in a large British birth cohort study [1]. In rodents, similarly to our previous work on perinatal co-exposure to MeHg and Labrador Tea [23], other investigators reported that co-administration of green tea extract to fish-fed rats led to higher blood mercury levels [34], and that mice co-exposed to green tea extract and MeHg presented higher muscle mercury levels than mice exposed to MeHg alone [35]. Together, these investigations suggest that dietary phytochemicals may interfere with MeHg absorption, distribution, metabolism and excretion.…”

“…Gamma glutamyl transferase (GGT) activity, which is involved in the biliary metabolism of MeHg-glutathione conjugate to the more easily reabsorbed MeHg-cysteine [13], was not significantly affected by any of the treatment groups (Table 1). Despite in vitro data suggesting that Labrador Tea may affect cytochrome p450 activities [36], no statistically significant perturbation of liver enzymatic activities (Table 1) was observed following exposure to Labrador Tea at a concentration previously shown to affect oxidative stress biomarkers and blood MeHg levels in developing rat pups [23].…”

“…subarcticum collection and characterization of the ethanolic extract were described by Black et al [24]. The same freeze-dried extract (Labrador Tea) conserved under nitrogen gas in amber vials at − 20 °C was used to dose rat pups in a previous study [23] and adult rats in this study. The corn oil (Mazola brand, ACH foods, Memphis, TN, USA) and cookies (Teddy Graham, Nabisco, Toronto, ON, Canada) were purchased from a local grocery store.…”

“…We previously reported that male and female rat pups developmentally exposed to MeHg and Labrador Tea (an antioxidant-rich Rhododendron tomentosum decoction consumed in Canadian Arctic communities) presented significantly higher blood mercury levels at weaning compared to pups exposed to the same MeHg dose administered alone [23]. In this follow-up study, adult male rats were exposed to the same daily dose of Labrador Tea or to an antibiotics cocktail (a positive control for gut bacteria inhibition) for 4 weeks (days 1 to 28), with or without concomitant daily exposure to MeHg for 3 weeks (days 8 to 28).…”

Mercury in the brain of polar bears (Ursus maritimus ) and ringed seals (Pusa hispida).

“…Also, there is evidence that compounds in the diet modulate the effects of Hg on the nervous system. Several plant extracts have been shown to protect against MeHg-induced neurodevelopmental toxicity and neurotoxicity in laboratory animals (Black et al 2011, Christinal and Sumathi 2013, Lucena et al 2013, Lucena et al 2010, Sumathi et al 2012. Other dietary components of wildlife and humans such as selenium (Se), found in fish, can diminish Hg-induced neurotoxicity (Berry and Ralston 2008, Beyrouty and Chan 2006, Yang et al 2008, while the protective effects o f fatty acids are still being discussed (Grotto et al 2011, Kaur et al 2011, Kaur et al 2008, Newland 2012, Rice 2008, Yang et al 2012.…”