Abstract: Objective To investigate the expression of thyroid stimulating hormone receptor (TSHR) in lymphoid nodes of BALB/c mice and in the mice treated with diethylstilbestrol (DES) during the neonatal period, and to explore the possible sources of thyroid stimulating hormone (TSH) expressed in the lymphoid nodes and the possible mechanism of the effect of DES on the expression of TSH.Methods Neonatal BALB/c mice whose weight discrepancies were less than 5% were divided randomly into a control group and a DES group. A total of 120 mice(30 pairs of females and 30 pairs of males) were chosen. Within 24 hours after birth, the mice in the DES group were injected subcutaneously at the cervix-backside with DES at intervals of 24 hours for 5 times, and the mice in the control group were injected with germfree bean oil using the same method. Mice were killed on postnatal day 7, 14, 21, 35, 49 and 63. 5 pairs of female mice and 5 pairs of male mice at each time point. Deep cervical lymph nodes were taken out, embedded in paraffin and sliced serially in a thickness of 4μm. The expression of TSHR in the lymphoid nodes was detected by immunohistochemistry technique. Results In both control and DES groups, TSHR positive cells were present in lymphoid nodes from postnatal day 7 to day 63. In female mice, the expression of TSHR reached peak on day 49 and in male mice on day 35. At each the same time point, the average absorbance (AEM>A/EM>) and the integrate absorbance (IEM>A/EM>) of TSHR expression were higher in the DES group than those in the control group. In female mice, statistic differences were showed in both AA and IEM>A/EM> between the two groups at all the time points, and in male mice statistic differences were showed in AEM>A/EM> on day 14, 21, 35 and 49 and in IA on day 14, 21, 35, 49 and 63 between the two groups. Conclusion TSHR positive cells are present in all the lymphoid nodes of both female and male BALB/c mice at all the detected time points. This suggests that the lymphocytes in lymphoid nodes of BALB/c mice during the postnatal period may have the receptor foundation of combing TSH which comes from antehypophysis. Expossure to DES during the neonatal period may lead an increased TSHR expression in lymphoid nodes of BALB/c mice, particularly in female mice. The effect of DES on the expression of TSHR in lymphocytes of both female and male mice may last up to adulthood of the mouse at least.

Key words: Lymphoid node, Diethylstilbestrol, Thyroid stimulating hormone receptor, Immunohistochemistry, Neonatal BALB/c mouse