Alterations of metallothionein isomers in Hg(0)-exposed rat brain.
Previously we found that exposure to mercury vapor effectively induced brain metallothionein (MT) in rats. Here, using FPLC-gel chromatography, we examined time-dependent alterations in the MT isomers, MT-I/II and MT-III, following 3 weeks of exposure. Rats were exposed to mercury vapor at 8.3 mg/m3 for 15 h in total over 5 consecutive days. Total MT levels in rat cerebrum and cerebellum increased by 65% and 155%, respectively, 24 h after the final exposure. The increased levels in both tissues remained unchanged for at least 2 weeks after termination of exposure. Interestingly, most MT in control rat cerebrum and cerebellum was accounted for by MT-III, with MT-I/II being less than 10%. Through mercury vapor exposure, MT-I/II was quickly induced to a significant extent in both tissues, reaching a level comparable to that of MT-III. The induction rate of MT-I/II in the cerebellum was somewhat higher than in the cerebrum. Chromatograms showed that the MT-I/II thus induced began to decline at an early stage in both tissues. In the cerebrum, the amount of MT-I/II on day 22 was about 30% of the maximum level on day 1. On the other hand, the induction of MT-III was not that dramatic, but it did become evident, at least in the latter stage, when MT-I/II had begun to decrease. Thus, though the induction rate of MT-III was not as high as MT-I/II, it was sustained throughout the experimental period.
Yasutake
A
A
Biochemistry Section, National Institute for Minamata Disease, Minamata, Kumamoto 867-0008, Japan. yasutake@nimd.go.jp
Nagano
M
M
Hirayama
K
K
D000280:Administration, Inhalation; D000818:Animals; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002849:Chromatography, Gas; D007536:Isomerism; D008297:Male; D008628:Mercury / Q000008:administration & dosage / Q000633:toxicity*; D008630:Mercury Poisoning / Q000378:metabolism*; D008668:Metallothionein / Q000032:analysis / Q000145:classification / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014835:Volatilization
D008668:Metallothionein; D008628:Mercury