The influence of in utero exposure to formaldehyde on newborn rat thymus structure

Aim. To study the structure of the thymus of newborn rats born from female rats exposed to inhalation of formaldehyde during gestation. Materials and Methods. The work was carried out on 72 white outbred rats of the first day of postnatal development. The first group consisted of newborn rats (n=37) – the offspring of six rats that were exposed to formaldehyde (FA) in concentration of 2.766 mg/m3 during the entire period of pregnancy. FA exposure was given once a day for 60 minutes in a 1 m3 exposure chamber. The second group included control animals (n=35), which were kept in conditions similar to those of the experimental groups with the exclusion of the effect of FA. In the newborn rats, the body mass and the absolute and relative mass of the thymus were determined. The structure of thymus was studied in a light optical microscope. The number of cells in the cortex and medulla of the thymus was counted over an area of 2500 μm2. Results. The body mass and absolute mass of thymus of the newborn rats of the first group showed a statistically significant reduction against control values. The differences between the values of relative mass of thymus in the compared groups were insignificant. The number of cells in the cortex and medulla of the thymus under the influence of FA did not show any significant changes. Conclusion. The effect of inhalation of FA on the organism of pregnant rats during the entire gestation period consists in a decrease in the body mass and in the absolute mass of the thymus of newborn rats. With this, the relative mass of the thymus did not undergo significant changes. The thymus structure in the light microscope did not show any significant changes either.