In vitro inhibition of thymulin production in mercury-exposed thymus of young mice

Lymphocyte differentiation, maturation and peripheral functions are affecte d by the thymic protein hormone thymulin. Mercury at very low concentration s has been seen to impair some lymphocytic functions causing subclinical ma nifestations in exposed workers. The present study was performed to test in vitro the effect of mercury on the production kinetics of thymulin using c ultures of whole thymuses from young mice. Exposure to mercury (10(-8) M an d 10(-6) M) added to the cultures, reduced kinetic thymulin production at a ll time intervals considered (1, 2, 4, 5 and 6 h) as compared to kinetic th ymulin production of thymuses from young control mice. After the first hour the inhibition is more evident at the highest mercury concentration. Thymu lin production decreased by 70, 74, 82 and 86% and by 55, 66, 73 and 81% fo r mercury concentrations of 10-6 M and 10-8 M, respectively, after 2, 4, 5 and 6 h. Mercury toxic effect on thymulin kinetics may be directly exerted to thymulin synthesis in epithelial cells, although it is less dramatic tha n that of cycloheximide (CHX), known as a potent inhibitor of protein synth esis in such cells. The toxic effect of mercury on thymic endocrine activit y might cause the subclinical effects on cell-mediated immunological status observed in mercury exposed workers. (C) 2001 Published by Elsevier Scienc e B.V. All rights reserved.