The expression of transporter genes was also increased following Hg0 vapor inhalation. The enhanced GST expression may imply the increased formation of mercury-glutathione conjugate for cellular efflux via multidrug resistance-associated proteins (MRP). The enhanced expression of MRP2 supports this assumption. In addition, the threefold increase in multidrug resistance gene (MDR1) encoded P-glycoprotein indicates that cellular mercury could also be pumped out of cellsbytheP-glycoproteinpump.Inaddition,theexpressionof genes encoding the zinc transporter ZnT1 and the organic cation transporter OCT1 was also increased. Alterations were also detected in signal transduction-related genes. The expression of genes encoding for acute-phase responses, such as c-jun/AP-1 complex, Nur 77 early response protein, and phosphatidylinostiol-3-kinase (PI3-p85) was depressed. On the other hand, the expression of genes encoding the protein kinase C alpha and protein kinase C gamma was enhanced. Mercury has a high affinity to lipid, and the expression of