Effects of Imuran on the Development of Thymus in the Rat Fetuses

consecutive daily doses of azathioprine 5mg and 15mg/kg body weight on the 4-5th, 8-9th and 12-13th day of gestation respectively for the study of the effect of azathioprine on the development of fetal thymus and lymphatic organs of the rat. Fetal body weights. external anomalies and fetal death or resorptions were examined. Thymus, spleen and lymph node were studied histologically in the Methyl Green-Pyronin, PAS, H-E and Silver stains on the day of 20th of gestation and on the Ist and 2nd weeks of neonatal age after their weights were measured. The results observed under ordinary microscope were as follows. In comparison with control groups, experimental groups were: 1. Fetal body weights were decreased slightly, but the weights of thymus and spleen were decreased conspicuously. 2. In the thymus, the number of immature thyrnocytes were increased in the cortex, hence the contrast between cortex and medulla was obscure. 3. In the lymph node, the formation of lymphatic nodule is delayed, and medium-sized or large lymphocytes were increased in number diffusely. 4. In the spleen, the number of medium-sized and large lymphocytes were increased in the inner portion of periarterial lymphocyte sheath and the size of white pulp was decreased. 5. In the thymus, spleen and lymph node, mast cells increased in number and reticular fibers appeared more densely. 6. Among the experimental groups, the groups of drug administration on the 4-5th or 7-8th day of gestation were affected more severely than the groups on the l2-13th day of gestation