Lactate dehydrogenase in preimplantation rabbit embryos.

Unfertilized eggs and early embryos up to the 2-day (16-cell) cleavage stage of development in the rabbit contain predominantly the most cathodal lactate dehydrogenase isoenzyme made up of A-type subunits. Following early cleavage there is a progressing increase in total LDH activity in the embryo as development proceeds through 4- and 6-day blastocyst stages. This is accompanied by an increase in the amount of B-type subunits and a concomitant shift in the lactate dehydrogenase isoenzyme electrophoretic pattern toward the anodal isoenzyme types.