A subchronic inhalation study with unleaded petrol in rats.

The effect of intermittent 2 months' exposure to 2 g/m3 unleaded petrol on the hypothalamo-pituitary-thyroid-adrenal system was evaluated by measuring hypothalamic noradrenaline (NA), serum corticosterone (CS), thyroxine (T4) and adrenal catecholamine (CA) levels in male rats. Serum CS and adrenal CA were increased and hypothalamic NA was decreased by exposure. No changes were observed in serum T4. Exposure induced an increase in spleen, kidney, liver and lung weights; weights of adrenals and hypothalamus were not changed. All the petrol-induced effects depended on the length of exposure. Rats exposed to petrol gained less weight than controls. The results suggest a non-specific stress response in the rat.