Binding of 63Ni(II) to ultrafiltrable constituents of rabbit serum in vivo and in vitro

Abstract

Binding of 63Ni(II) to ultrafiltrable constituents of rabbit serum was studied (a) after in vitro incubation (2 h, 37 °C) of rabbit serum with 63NiCl2 (10-100 μmol/liter), and (b) at intervals (0.25-2h) after in vivo administration of 63NiCl2 (40-160 μmol/kg body wt, i.v.). Serum ultrafiltrates were fractionated by thin layer chromatography, and the separated compounds made visible by autoradiography and by ninhydrin staining. Several (5) ultrafiltrable 63Ni complexes were demonstrable as distinct radiodense 63Ni bands with chromatographic mobilities corresponding to those of ninhydrin positive bands. Unbound 63Ni(II) was not detected in serum ultrafiltrates in either the in vitro or in vivo experiments. In sera (n=10) incubated in vitro with 63Ni(II) (10 μmol/liter), the mean percentage of ultrafiltrable 63Ni was 36% (range = 33-38) of total serum 63Ni. In contrast, in sera (n=10) obtained 2 h after i.v. injection of 63Ni(II) (40 μmol/kg), the mean concentration of total serum 63Ni was 10.8 μmol/liter (range=6-14), and the mean percentage of ultrafiltrable 63Ni was 15% (range = 9-21) of total serum 63Ni. The disparity between the percentages of ultrafiltrable 63Ni obtained in vitro and in vivo was obviated when the in vivo experiments were performed in rabbits bilaterally nephrectomized, with ligated common bile ducts. This investigation confirms the existence of several nickel receptors in serum ultrafiltrates and substantiates the role of ultrafiltrable complexes in the excretion of nickel. (Journal received: 9 July 1976)