Effect on the histological structure of thymus on sprague-dawley treated with arsenic trioxide

In coastal areas of northern Chile medium or high levels of arsenic are commonly found in drinking water. Arsenic exposure may be associated with acute or chronic effects. The objective of this investigation was to determine the histological damage caused by arsenic trioxide level of the compartments of the thymus of Sprague-Dawley rats. We used 24 rats of both sexes of 55 days of life. The rats were weighed and divided into 3 groups (4 females and 4 males). In the treated groups were administered 5 mg and 10 mg of As₂O₃ respectively, in a single daily dose for 15 days intraperitoneally. The control group was administered distilled water without arsenic. After treatment the animals were sacrificed and the thymus removed, washed, weighed and divided into two, then fixed in 10% buffered formalin. By conventional histology samples were obtained serially every 4 thymus, 5 microns thick and separated by 100 microns each, then were stained with HE. We analyzed 30 fields (120 fields per organ). The results showed that As₂O₃ causes loss of cellularity in both compartments of the thymus, both in the cortex and in the bone, medullary compartment was more affected (near the corticomedullary junction). There was a significant reduction in the size of the medulla in both groups (5 and 10 mg As₂O₃ respectively), probably the decrease of the tissue responsible for thymic atrophy. We observed an increase in the size of the cortex in female rats treated with 10 mg of As₂O₃. The corticomedullary junction of the treated rats showed diffuse or difficult to distinguish.