Hookah (shisha, narghile, “water pipe”) indoor air contamination in German unrealistic experiment. Serious methodological biases and ethical concern

Metallothionein (MT) is a low-molecular weight sulfur-rich protein that plays role in metal homeostasis/detoxification and radical scavenging. The following study investigated the ability of exogenous MT to protect against oxidative damage induced by thallium (TI) in rat liver. Male Wistar rats were divided into four groups; a control and three experimental groups. The control group received physiological saline. Group 1 animals were injected with thallium acetate intraperitoneally (i.p.) at a single dose of LD50 (32 mg/kg). In group 2 and group 3, metallothionein I was administrated once at two different doses (1 or 2.5 mg/kg i.p., respectively) 1 h before TI intoxication. Levels of endogenous antioxidants, oxidative stress markers were measured and histopathological examinations were performed 4 days after TI administration. TI accumulation in liver decreased related to the dose of MT. Mostly all of the alterations in the levels antioxidants restored to normal levels in MT administrated animals. H2O2 levels and lipid peroxidation decreased, integrity of hepatocytes and membranous structures inside the cells were preserved. The toxic effects of TI were modulated in MT administrated animals particularly at the dose of 2.5 mg/kg. These findings suggest an active role of exogenous MT against TI-induced oxidative stress in rat liver.