ON MERCURY AND SELENIUM IN FISH BLOOD .5. GLUTATHIONE-PEROXIDASE ACTIVITY IN THE BLOOD OF TUNAS AND MARLINS

The glutathione peroxidase activity (GHS-P-x) in eleven blood specimen s of two species of tuna, i.e., nine individuals of yellow fin tuna Th unnus albacares and two individuals of big-eyed tuna Thunnus obesus, a nd in seven blood specimens of four species of marlin, i.e., three ind ividuals of striped marlin Tetrapturus audax, two individuals of blue marlin Makaira mazara, one individual of swordfish Xiphias gladius and one individual of sailfish Istipohorus platyterus, are presented in r elation to the distribution of selenium and mercury. GSH-P-x in the bl ood of tunas was high compared with that of marlins, as in the cases o f the selenium and mercury concentrations. In both species, GSH-P-x di d not significantly correlate with the concentration of the low oxidat ion state of selenium. On the other hand, GSH-P-x correlated netativel y with the total mercury concentration in the case of marlins while th ere was no correlation in the case of tunas. These findings may sugges t that since there are few protein-containing selenohydryl groups with mercury as organic selenium in the blood of marlins, GSH-P-x tends to drastically decrease with mercury accumulation.