Clinical Chemistry, Vol 21, 521-527, Copyright © 1975 by the American Association for Clinical Chemistry

Binding of ⁶³Ni(II) to Ultrafiltrable Constituents of Rabbit Serum In Vivo and In Vitro

¹ Department of Laboratory Medicine, University of Connecticut School of Medicine, Farmington, Conn. 06032.

F. William Sunderman, Jr., M.D., University of Connecticut Health Center, P.0. Box G, Farmington, Conn. 06032.

Binding of ⁶³Ni(Il) 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 (0.25-2 h) 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.