Uptake and release of63Ni2+ byXenopus embryos during early cleavage stages |
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Authors: | F William Sunderman Jr Frank J Mongillo Marilyn C Plowman Sean M Brennan |
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Institution: | (1) Departments of Laboratory Medicine, University of Connecticut School of Medicine, 06032 Farmington, CT, USA;(2) Departments of Pharmacology, University of Connecticut School of Medicine, 06032 Farmington, CT, USA;(3) Departments of Anatomy, University of Connecticut School of Medicine, 06032 Farmington, CT, USA;(4) University of Connecticut Medical School, 263 Farmington Avenue, 06032 Farmington, CT, USA |
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Abstract: | Summary Uptake and release of63Ni was studied in dejelliedXenopus laevis embryos exposed to63Ni2+ (0.3–30 mol/1) for 0.5-h intervals during the period 1–4.5 h post-fertilization (i.e. from first cleavage to early blastula stage). At first cleavage, the mean uptake of63Ni by embryos was 12-17 times that by non-fertilized eggs, suggesting that conversion of the vitelline envelope to the fertilization envelope enhanced integumental permeability to63Ni2+. 63 Ni uptake by embryos at the 1-2-cell stage averaged 1.8–2.5 times that at the early blastula stage. An average of 5% of total63Ni in washed embryos was recovered in isolated fertilization envelopes, indicating that63Ni2+ passed through the envelope into internal compartments. Progressive increases of63Ni uptake were seen with increasing exposure levels; after exposure during 1–1.5 h post-fertilization to the highest concentration of63Ni2+ (30 mol/1),63Ni uptake averaged 11.4 (SD±5.1) pmol/embryo. Rapid efflux of63Ni was noted after63Ni2+-exposed embryos were transferred to nickel-free medium; mean63Ni contents at 0.25 h and 2 h post-exposure diminished to 50% and 15% of the initial values, regardless of the exposure level. The finding thatXenopus embryos are permeable to63Ni2+ during early cleavage stages provides a convenient experimental system to investigate the embryotoxicity and teratogenicity of nickel. |
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Keywords: | Nickel metabolism Nickel toxicology Xenopus laevis Embryogenesis |
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