An examination of the oxidation of mercury vapor by rat brain homogenate.
The oxidation of mercury vapor (Hg degrees) to divalent inorganic mercury (Hg2+) was studied in rat brain homogenates. By using a "degassing" method, it was possible to speciate the mercury present in the homogenate and, for the first time, to measure the rate of oxidation as a function of the substrate (Hg degrees) concentration. Mercury oxidation was first-order with respect to substrate concentration at all concentrations tested, and the first-order rate constant for the oxidation process was proportional to homogenate concentration. The role of catalase compound I in mercury vapor oxidation by brain homogenate was examined by observing the effects of two inhibitors of catalase (catalase compound I) on homogenate mercury-oxidizing activity and catalase activity. Sodium azide (50 mM) completely inhibited both mercury-oxidizing activity and catalase activity. Aminotriazole (3-amino-1H-1,2,4-triazole) (50 mM) completely inhibited only mercury-oxidizing activity; some residual catalase activity was found in the aminotriazole-treated homogenate. It was concluded that catalase compound I plays a major role in the oxidation of Hg degrees, but the possibility that catalase-independent pathways make a minor contribution cannot be excluded.
Sichak
S P
SP
Division of Toxicology, University of Rochester School of Medicine, NY.
Mavis
R D
RD
Finkelstein
J N
JN
Clarkson
T W
TW
D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D001386:Azides / Q000494:pharmacology; D001921:Brain / Q000201:enzymology / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D007700:Kinetics; D008628:Mercury / Q000493:pharmacokinetics*; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D019810:Sodium Azide
D001386:Azides; D019810:Sodium Azide; D002374:Catalase; D008628:Mercury; D000640:Amitrole