Hormonal and organ weight changes in rats exposed to simultaneous chronic effects of CO and NO2

Activity of the pituitary-adrenocortical, sympathico-adrenomedullary and thyroid gland systems was examined in groups of male adult rats, average weight 180 g, exposed for 2 months to a mixture of 7 mg.m-3 NO2 and 32 mg.m-3 CO in air and in groups of matched controls inhaling fresh air. Corticosterone (B) concentrations in the serum of rats were determined by the competitive protein-binding method, noradrenaline (NA) in the hypothalamus and catecholamines (CA) in suprarenals by fluorometry, thyroxine (T4) and triiodothyronine (T3) in the thyroid gland by the RIA technique. Measurements of organ weight were related to overall body weight. The data emerging from this study were evaluated using the Student t-test.

one-month exposure led to a decrease in hypothalamic NA and an increase in rat spleen weight; increase in CA concentration in the adrenals was initially insignificant, by the end of a 2-month exposure it reached the level of statistical significance; serum concentrations of B, T3 and T4 remained unaffected and so was the weight of the body, liver, lungs, suprarenals and the hypothalamus of exposed rats; at the concentrations used, NO2 and CO acted as synergists producing a mild stressogenic reaction affecting the activity of the sympathico-adrenomedullary system of exposed rats.