Investigation of Excitatory and Inhibitory Effects of L-Arginine and L-NAME on the thickness of the cortex and medulla of Thymus in Pregnant Rats

Considering the important role of Nitric Oxide (NO) in many biologic processes of cells and tissues including during pregnancy and its different stages, this study investigated the effects of L-Arginine as a NO precursor and L-NAME as a NO inhibitor on structural and stereological changes of the thymus in pregnant rats. In this experimental study, thirty-two female Wistar rats, aged 8 weeks and weighing 200-250g, were randomly divided into 4 groups: Control, L-Arginine (200 mg / kg), L-NAME (20 mg / kg) and L-Arginine + L-NAME; 8 rats in each group. On the 18th day of pregnancy, the rats anesthetized with ether, then, their thymus was extracted and fixed in 10% formalin. After tissue passage, the sections were stained with H&E and the histological and morphometric studies were performed. L-Arginine with its stimulative effect on NO synthesis in thymus causes to increase T-lymphocyte population, therefore thickness of cortex is increased and thickness of medulla decreased. Analysis of variance showed that the thickness of cortex and medulla of thymus in the L-Arginine group was significantly different in comparison with the control group, with p=0.000 and p=0.002, respectively. The thickness of cortex and medulla in the L-NAME group showed a significant decrease, with p=0.000, compared to the control group.