The metabolism of inhaled mercury vapor in the rat studied by isotope techniques.

The metabolism of inhaled mercury vapor in the rat has been studied, using Hg 203 as a tracer, following short periods of exposure (½ to 5 hours) in a specially constructed exposure unit. The distribution and excretion patterns are remarkably similar to those obtained with HgCl 2 given by intravenous or intramuscular injection. The only major difference associated with the inhalation route is a transient, high level in the lungs, that clears with a half-time of 5 hours. By calculation from assumed minute volumes, virtually all of the inhaled mercury vapor is apparently deposited in the lung, there oxidized to ionic form and absorbed by the blood within a matter of hours. About 30% of the metal is cleared from the body rapidly (half-time, 2 days) and the rest more slowly (half-time, 20 days). The rapid phase is associated with a transient, rapid fecal excretion, the slow phase with approximately equal rates of fecal and urinary excretion. Apart from the transient high levels in the lung, mercury is uniformly distributed in all tissues except the kidney. After 15 days, the latter organ has accumulated 70% or more of the body burden. On a per gram basis, the kidney at that time contains 150 times as high a concentration of the metal as the other tissues. The extraordinary affinity of the kidney for mercury is not related to filtration phenomena.