Effect of mercurials on lymphocyte functions in vitro.

The effect of in vitro treatment with mercurials on several functions of mouse lymphocytes was studied. When lymphocytes were cultured in the presence of mercurials, DNA synthesis induced by mitogen (concanavalin A, phytohemagglutinin-P, lipopolysaccharide) and polyclonal B cell activation induced by lipopolysaccharide were strongly inhibited by methylmercuric chloride at the concentration of 10(-6) M, but mercuric chloride inhibited these functions by 50% at 10(-5) M. Furthermore, 10(-7) M methylmercuric chloride and 10(-6) M mercuric chloride inhibited mixed lymphocyte reaction by 80%. Thus, the inhibitory effect of methylmercuric chloride was 10 times stronger than that of mercuric chloride when the mercurials were present in the culture throughout the incubation. On the other hand, DNA synthesis once induced by mitogens was not significantly affected when 10(-6) M methylmercury was added during the last 3 h of the incubation. Pretreatment with 10(-6) M methylmercury for 1 h, however, showed 50% inhibition of thymidine incorporation into DNA and also reduced the rate of metabolism of phosphatidyl inositol by 50%. These results indicate that methylmercury may act on mouse lymphocytes at an early stage of transformation induced by the mitogens, while inorganic mercury failed to cause the pronounced difference in its potency of inhibition on the functions of lymphocytes by the different treatments of the cells under the various conditions used.