Effect of methyl mercury exposure on the uptake of radiolabeled inorganic mercury in the brain of rabbits.

Exposure to mercuric compounds at high dose levels has previously been shown to alter the integrity and function of the blood-brain barrier in laboratory animals. In the present study, we have investigated the distribution of intravenously administered inorganic 203Hg in rabbits additionally exposed to MeHg. A single dose of 203HgCl2 was administered together with or 5 min. or 24 hr after administration of a single dose (10 or 37.5 mumol/kg b.wt.) of MeHg. In another experiment, 203HgCl2 was administered to rabbits subchronically exposed to MeHg (1 mumol/kg b.wt. daily for three weeks) 24 hr after cessation of treatment. The integrity of the blood-brain barrier was assayed by measuring the uptake of 203Hg in the brain, as the blood-brain barrier usually serves to exclude inorganic Hg from the brain. The concentration of 203Hg within the brain was similar in all MeHg-treated rabbits, corresponding to 0.02% of the administered dose, and not different from that of control animals. Under these conditions, no obvious damage to the blood-brain barrier by MeHg could be observed.