Permeability of intact and dechorionated zebra fish embryos to glycerol and dimethyl sulfoxide.

Intact developing embryos of the zebra fish Brachydanio rerio were exposed to [14C]DMSO and [3H]glycerol (1 M in Fish Ringer) to assess the degree of permeation of these cryoprotectants. Glycerol enters the embryo more easily, although reaching only about 8% of the expected equilibrium level after 2 hr at room temperature; DMSO reaches only about 2.5% of this level. In an attempt to identify the barrier to permeation, dechorionated embryos were similarly exposed to isotopic DMSO. Permeation increased severalfold, indicating that the chorion retards the free exchange of solute. Embryos are unaffected by exposure to 1 M DMSO in Fish Ringer at 23 degrees C for up to 1 hr. The number of embryos hatching after 1-hr exposure to DMSO at varying concentrations was significantly reduced at 1.5 and 2 M. Embryos exposed to 1 M glycerol for 1 hr at 23 degrees C showed disruption of periblast cells and separation of the blastoderm; it was impossible to remove glycerol either by abrupt or very slow dilution.