Different distribution of cadmium in the liver supernatant between in vivo and in vitro.

Distribution of cadmium (Cd) in liver supernatant was examined by gel filtration chromatography after injecting Cd intravenously into female Wistar rats and also by adding Cd in vitro into the control supernatant. Supernatants were analyzed on an HPLC Asahipak GST-520 column and on-line ICP (inductively coupled argon plasma-atomic emission spectrometer) analysis of the eluate (HPLC-ICP). The relative intensity of the three main Cd-associated peaks changed with time after injection of Cd into rats. The three peaks were tentatively assigned as Cd-binding protein-I and -II (Cd-BP-I and -II) and metallothionein (MT) in the order of respective elution from the column. Relative affinities of Cd for the three peaks were determined by injecting different doses of Cd into rats as follows: MT greater than Cd-BP-II greater than Cd-BP-I. Cd-BP-II was assigned as the major Cd-BP other than MT in the liver supernatant and it contained zinc that can be replaced by Cd. Comparison between the in vivo and in vitro Cd distributions indicated that the former distribution is not reproducible under any in vitro conditions examined and the latter distribution is dependent mostly upon incubation temperature.