Uptake and release of 63Ni2+ by Xenopus embryos during early cleavage stages.
Uptake and release of 63Ni was studied in dejellied Xenopus laevis embryos exposed to 63Ni2+ (0.3-30 mumol/l) 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 of 63Ni 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 to 63Ni2+. 63Ni 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 total 63Ni in washed embryos was recovered in isolated fertilization envelopes, indicating that 63Ni2+ passed through the envelope into internal compartments. Progressive increases of 63Ni uptake were seen with increasing exposure levels; after exposure during 1-1.5 h post-fertilization to the highest concentration of 63Ni2+ (30 mumol/l), 63Ni uptake averaged 11.4 (SD +/- 5.1) pmol/embryo. Rapid efflux of 63Ni was noted after 63Ni2(+)-exposed embryos were transferred to nickel-free medium; mean 63Ni 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 that Xenopus embryos are permeable to 63Ni2+ during early cleavage stages provides a convenient experimental system to investigate the embryotoxicity and teratogenicity of nickel.
Sunderman
F W
FW
Department of Laboratory Medicine, University of Connecticut School of Medicine, Farmington 06032.
Mongillo
F J
FJ
Plowman
M C
MC
Brennan
S M
SM
D000818:Animals; D001693:Biological Transport, Active; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism; D009532:Nickel / Q000493:pharmacokinetics* / Q000633:toxicity; D010063:Ovum / Q000378:metabolism; D011868:Radioisotopes; D013723:Teratogens; D013997:Time Factors; D014982:Xenopus laevis / Q000196:embryology / Q000378:metabolism*
D011868:Radioisotopes; D013723:Teratogens; D009532:Nickel