POSTTRANSCRIPTIONAL ELEVATION OF MOUSE-BRAIN MN-SOD PROTEIN BY MERCURIC-CHLORIDE

Alterations in gene expression, protein content and enzyme activity of brain Mn-SOD following mercuric chloride (HgCl2) exposure were examin ed in ICR male mice. Subcutaneous administration of HgCl2 (1 mg Hg/kg) resulted in a significant increase (4-fold) in the brain Mn-SOD conte nt at 6 h after injection while the total mercury concentration was ab out 0.11 mu g/g of brain. The enhancement of Mn-SOD protein caused by HgCl2 was completely abolished by pretreatment with dexamethasone (3 m g/kg) 1 h prior to HgCl2 administration, suggesting involvement of inf lammation in inorganic mercury-induced increase in the antioxidant enz yme. This increase in level of Mn-SOD content coincided with a substan tial rise in the enzyme activity; however, Northern blot analysis reve aled that the induction of protein level was not due to that of its ge ne expression. The results of the present study indicate that mouse br ain Mn-SOD appears to undergo post-translational modification by the e nvironmental toxic metal, and induction of the antioxidant enzyme coul d be of an initial response to the metal-induced oxidative stress. (C) 1997 Elsevier Science B.V.