Valence states of plasma chromium in rats after intraperitoneal administration of sodium chromate.

It is well known that soluble chromates, when added to blood in vitro or in vivo, hardly interact with the plasma components and easily penetrate the erythrocytes, and that reduction to the trivalent species follows.1-3) However, in vitro reduction of chromium(VI) in human4) and rat5) plasma has been observed. Some problems of the fate of chromium(VI) in blood, especially in vivo remain unsolved, because of the difficulty in determining this chromium species in biological samples. For studying these problems, suitable analytical methods for the determination of chromium(VI) in biological samples are required. Recently, high-performance liquid chromatography (HPLC) with an anionexchange column (FPLC system with Mono Q HR 5/5, Pharmacia, Sweden) was reported to be useful for the determination of water-soluble chromium(VI).6) Using this method, the reduction of chromium(VI) in plasma, erythrocyte lysate and soluble fractions of the livers of rats has been examined after addition of sodium chromate to the samples in vitro.5) In the present experiment, the plasma of rats injected intraperitoneally (ip) with Na2CrO4 was examined for the presence of chromium(VI), using this HPLC method. The fate of this chromium species in blood will be also discussed. Male adult rats (360-430 g) of the Sprague-Dawley strain (Clea Japan, Tokyo, Japan), fed on a commercial pelleted diet (CE-2, Clea Japan) and sterilized tap water ad libitum, were injected with a saline solution [1 mg chromium(VI)/ml, 5 mg chromium(VI)/kg body weight] of Na2CrO4• 4H2O (analytical reagent grade, J. T. Baker, Phillipsburg, Nj, U.S.A.). Blood was taken from the hearts of Nembutal-anesthetized animals with heparinized syringes at 5, 10, 20, 40 and 60 min after injection. The blood was centrifuged at 3000 rpm for 10 min at 4•Ž and the plasma was separated. The plasma samples were immediately analyzed for chromium(VI) by the anion-exchange HPLC described above. The eluates were also examined for total chromium by atomic absorption spectro-